go value 源码
golang value 代码
文件路径：/src/reflect/value.go
// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package reflect
import (
"errors"
"internal/abi"
"internal/goarch"
"internal/itoa"
"internal/unsafeheader"
"math"
"runtime"
"unsafe"
)
// Value is the reflection interface to a Go value.
//
// Not all methods apply to all kinds of values. Restrictions,
// if any, are noted in the documentation for each method.
// Use the Kind method to find out the kind of value before
// calling kind-specific methods. Calling a method
// inappropriate to the kind of type causes a run time panic.
//
// The zero Value represents no value.
// Its IsValid method returns false, its Kind method returns Invalid,
// its String method returns "<invalid Value>", and all other methods panic.
// Most functions and methods never return an invalid value.
// If one does, its documentation states the conditions explicitly.
//
// A Value can be used concurrently by multiple goroutines provided that
// the underlying Go value can be used concurrently for the equivalent
// direct operations.
//
// To compare two Values, compare the results of the Interface method.
// Using == on two Values does not compare the underlying values
// they represent.
type Value struct {
// typ holds the type of the value represented by a Value.
typ *rtype
// Pointer-valued data or, if flagIndir is set, pointer to data.
// Valid when either flagIndir is set or typ.pointers() is true.
ptr unsafe.Pointer
// flag holds metadata about the value.
// The lowest bits are flag bits:
// - flagStickyRO: obtained via unexported not embedded field, so read-only
// - flagEmbedRO: obtained via unexported embedded field, so read-only
// - flagIndir: val holds a pointer to the data
// - flagAddr: v.CanAddr is true (implies flagIndir)
// - flagMethod: v is a method value.
// The next five bits give the Kind of the value.
// This repeats typ.Kind() except for method values.
// The remaining 23+ bits give a method number for method values.
// If flag.kind() != Func, code can assume that flagMethod is unset.
// If ifaceIndir(typ), code can assume that flagIndir is set.
flag
// A method value represents a curried method invocation
// like r.Read for some receiver r. The typ+val+flag bits describe
// the receiver r, but the flag's Kind bits say Func (methods are
// functions), and the top bits of the flag give the method number
// in r's type's method table.
}
type flag uintptr
const (
flagKindWidth = 5 // there are 27 kinds
flagKindMask flag = 1<<flagKindWidth - 1
flagStickyRO flag = 1 << 5
flagEmbedRO flag = 1 << 6
flagIndir flag = 1 << 7
flagAddr flag = 1 << 8
flagMethod flag = 1 << 9
flagMethodShift = 10
flagRO flag = flagStickyRO | flagEmbedRO
)
func (f flag) kind() Kind {
return Kind(f & flagKindMask)
}
func (f flag) ro() flag {
if f&flagRO != 0 {
return flagStickyRO
}
return 0
}
// pointer returns the underlying pointer represented by v.
// v.Kind() must be Pointer, Map, Chan, Func, or UnsafePointer
// if v.Kind() == Pointer, the base type must not be go:notinheap.
func (v Value) pointer() unsafe.Pointer {
if v.typ.size != goarch.PtrSize || !v.typ.pointers() {
panic("can't call pointer on a non-pointer Value")
}
if v.flag&flagIndir != 0 {
return *(*unsafe.Pointer)(v.ptr)
}
return v.ptr
}
// packEface converts v to the empty interface.
func packEface(v Value) any {
t := v.typ
var i any
e := (*emptyInterface)(unsafe.Pointer(&i))
// First, fill in the data portion of the interface.
switch {
case ifaceIndir(t):
if v.flag&flagIndir == 0 {
panic("bad indir")
}
// Value is indirect, and so is the interface we're making.
ptr := v.ptr
if v.flag&flagAddr != 0 {
// TODO: pass safe boolean from valueInterface so
// we don't need to copy if safe==true?
c := unsafe_New(t)
typedmemmove(t, c, ptr)
ptr = c
}
e.word = ptr
case v.flag&flagIndir != 0:
// Value is indirect, but interface is direct. We need
// to load the data at v.ptr into the interface data word.
e.word = *(*unsafe.Pointer)(v.ptr)
default:
// Value is direct, and so is the interface.
e.word = v.ptr
}
// Now, fill in the type portion. We're very careful here not
// to have any operation between the e.word and e.typ assignments
// that would let the garbage collector observe the partially-built
// interface value.
e.typ = t
return i
}
// unpackEface converts the empty interface i to a Value.
func unpackEface(i any) Value {
e := (*emptyInterface)(unsafe.Pointer(&i))
// NOTE: don't read e.word until we know whether it is really a pointer or not.
t := e.typ
if t == nil {
return Value{}
}
f := flag(t.Kind())
if ifaceIndir(t) {
f |= flagIndir
}
return Value{t, e.word, f}
}
// A ValueError occurs when a Value method is invoked on
// a Value that does not support it. Such cases are documented
// in the description of each method.
type ValueError struct {
Method string
Kind Kind
}
func (e *ValueError) Error() string {
if e.Kind == 0 {
return "reflect: call of " + e.Method + " on zero Value"
}
return "reflect: call of " + e.Method + " on " + e.Kind.String() + " Value"
}
// valueMethodName returns the name of the exported calling method on Value.
func valueMethodName() string {
var pc [5]uintptr
n := runtime.Callers(1, pc[:])
frames := runtime.CallersFrames(pc[:n])
var frame runtime.Frame
for more := true; more; {
const prefix = "reflect.Value."
frame, more = frames.Next()
name := frame.Function
if len(name) > len(prefix) && name[:len(prefix)] == prefix {
methodName := name[len(prefix):]
if len(methodName) > 0 && 'A' <= methodName[0] && methodName[0] <= 'Z' {
return name
}
}
}
return "unknown method"
}
// emptyInterface is the header for an interface{} value.
type emptyInterface struct {
typ *rtype
word unsafe.Pointer
}
// nonEmptyInterface is the header for an interface value with methods.
type nonEmptyInterface struct {
// see ../runtime/iface.go:/Itab
itab *struct {
ityp *rtype // static interface type
typ *rtype // dynamic concrete type
hash uint32 // copy of typ.hash
_ [4]byte
fun [100000]unsafe.Pointer // method table
}
word unsafe.Pointer
}
// mustBe panics if f's kind is not expected.
// Making this a method on flag instead of on Value
// (and embedding flag in Value) means that we can write
// the very clear v.mustBe(Bool) and have it compile into
// v.flag.mustBe(Bool), which will only bother to copy the
// single important word for the receiver.
func (f flag) mustBe(expected Kind) {
// TODO(mvdan): use f.kind() again once mid-stack inlining gets better
if Kind(f&flagKindMask) != expected {
panic(&ValueError{valueMethodName(), f.kind()})
}
}
// mustBeExported panics if f records that the value was obtained using
// an unexported field.
func (f flag) mustBeExported() {
if f == 0 || f&flagRO != 0 {
f.mustBeExportedSlow()
}
}
func (f flag) mustBeExportedSlow() {
if f == 0 {
panic(&ValueError{valueMethodName(), Invalid})
}
if f&flagRO != 0 {
panic("reflect: " + valueMethodName() + " using value obtained using unexported field")
}
}
// mustBeAssignable panics if f records that the value is not assignable,
// which is to say that either it was obtained using an unexported field
// or it is not addressable.
func (f flag) mustBeAssignable() {
if f&flagRO != 0 || f&flagAddr == 0 {
f.mustBeAssignableSlow()
}
}
func (f flag) mustBeAssignableSlow() {
if f == 0 {
panic(&ValueError{valueMethodName(), Invalid})
}
// Assignable if addressable and not read-only.
if f&flagRO != 0 {
panic("reflect: " + valueMethodName() + " using value obtained using unexported field")
}
if f&flagAddr == 0 {
panic("reflect: " + valueMethodName() + " using unaddressable value")
}
}
// Addr returns a pointer value representing the address of v.
// It panics if CanAddr() returns false.
// Addr is typically used to obtain a pointer to a struct field
// or slice element in order to call a method that requires a
// pointer receiver.
func (v Value) Addr() Value {
if v.flag&flagAddr == 0 {
panic("reflect.Value.Addr of unaddressable value")
}
// Preserve flagRO instead of using v.flag.ro() so that
// v.Addr().Elem() is equivalent to v (#32772)
fl := v.flag & flagRO
return Value{v.typ.ptrTo(), v.ptr, fl | flag(Pointer)}
}
// Bool returns v's underlying value.
// It panics if v's kind is not Bool.
func (v Value) Bool() bool {
// panicNotBool is split out to keep Bool inlineable.
if v.kind() != Bool {
v.panicNotBool()
}
return *(*bool)(v.ptr)
}
func (v Value) panicNotBool() {
v.mustBe(Bool)
}
var bytesType = TypeOf(([]byte)(nil)).(*rtype)
// Bytes returns v's underlying value.
// It panics if v's underlying value is not a slice of bytes or
// an addressable array of bytes.
func (v Value) Bytes() []byte {
// bytesSlow is split out to keep Bytes inlineable for unnamed []byte.
if v.typ == bytesType {
return *(*[]byte)(v.ptr)
}
return v.bytesSlow()
}
func (v Value) bytesSlow() []byte {
switch v.kind() {
case Slice:
if v.typ.Elem().Kind() != Uint8 {
panic("reflect.Value.Bytes of non-byte slice")
}
// Slice is always bigger than a word; assume flagIndir.
return *(*[]byte)(v.ptr)
case Array:
if v.typ.Elem().Kind() != Uint8 {
panic("reflect.Value.Bytes of non-byte array")
}
if !v.CanAddr() {
panic("reflect.Value.Bytes of unaddressable byte array")
}
p := (*byte)(v.ptr)
n := int((*arrayType)(unsafe.Pointer(v.typ)).len)
return unsafe.Slice(p, n)
}
panic(&ValueError{"reflect.Value.Bytes", v.kind()})
}
// runes returns v's underlying value.
// It panics if v's underlying value is not a slice of runes (int32s).
func (v Value) runes() []rune {
v.mustBe(Slice)
if v.typ.Elem().Kind() != Int32 {
panic("reflect.Value.Bytes of non-rune slice")
}
// Slice is always bigger than a word; assume flagIndir.
return *(*[]rune)(v.ptr)
}
// CanAddr reports whether the value's address can be obtained with Addr.
// Such values are called addressable. A value is addressable if it is
// an element of a slice, an element of an addressable array,
// a field of an addressable struct, or the result of dereferencing a pointer.
// If CanAddr returns false, calling Addr will panic.
func (v Value) CanAddr() bool {
return v.flag&flagAddr != 0
}
// CanSet reports whether the value of v can be changed.
// A Value can be changed only if it is addressable and was not
// obtained by the use of unexported struct fields.
// If CanSet returns false, calling Set or any type-specific
// setter (e.g., SetBool, SetInt) will panic.
func (v Value) CanSet() bool {
return v.flag&(flagAddr|flagRO) == flagAddr
}
// Call calls the function v with the input arguments in.
// For example, if len(in) == 3, v.Call(in) represents the Go call v(in[0], in[1], in[2]).
// Call panics if v's Kind is not Func.
// It returns the output results as Values.
// As in Go, each input argument must be assignable to the
// type of the function's corresponding input parameter.
// If v is a variadic function, Call creates the variadic slice parameter
// itself, copying in the corresponding values.
func (v Value) Call(in []Value) []Value {
v.mustBe(Func)
v.mustBeExported()
return v.call("Call", in)
}
// CallSlice calls the variadic function v with the input arguments in,
// assigning the slice in[len(in)-1] to v's final variadic argument.
// For example, if len(in) == 3, v.CallSlice(in) represents the Go call v(in[0], in[1], in[2]...).
// CallSlice panics if v's Kind is not Func or if v is not variadic.
// It returns the output results as Values.
// As in Go, each input argument must be assignable to the
// type of the function's corresponding input parameter.
func (v Value) CallSlice(in []Value) []Value {
v.mustBe(Func)
v.mustBeExported()
return v.call("CallSlice", in)
}
var callGC bool // for testing; see TestCallMethodJump and TestCallArgLive
const debugReflectCall = false
func (v Value) call(op string, in []Value) []Value {
// Get function pointer, type.
t := (*funcType)(unsafe.Pointer(v.typ))
var (
fn unsafe.Pointer
rcvr Value
rcvrtype *rtype
)
if v.flag&flagMethod != 0 {
rcvr = v
rcvrtype, t, fn = methodReceiver(op, v, int(v.flag)>>flagMethodShift)
} else if v.flag&flagIndir != 0 {
fn = *(*unsafe.Pointer)(v.ptr)
} else {
fn = v.ptr
}
if fn == nil {
panic("reflect.Value.Call: call of nil function")
}
isSlice := op == "CallSlice"
n := t.NumIn()
isVariadic := t.IsVariadic()
if isSlice {
if !isVariadic {
panic("reflect: CallSlice of non-variadic function")
}
if len(in) < n {
panic("reflect: CallSlice with too few input arguments")
}
if len(in) > n {
panic("reflect: CallSlice with too many input arguments")
}
} else {
if isVariadic {
n--
}
if len(in) < n {
panic("reflect: Call with too few input arguments")
}
if !isVariadic && len(in) > n {
panic("reflect: Call with too many input arguments")
}
}
for _, x := range in {
if x.Kind() == Invalid {
panic("reflect: " + op + " using zero Value argument")
}
}
for i := 0; i < n; i++ {
if xt, targ := in[i].Type(), t.In(i); !xt.AssignableTo(targ) {
panic("reflect: " + op + " using " + xt.String() + " as type " + targ.String())
}
}
if !isSlice && isVariadic {
// prepare slice for remaining values
m := len(in) - n
slice := MakeSlice(t.In(n), m, m)
elem := t.In(n).Elem()
for i := 0; i < m; i++ {
x := in[n+i]
if xt := x.Type(); !xt.AssignableTo(elem) {
panic("reflect: cannot use " + xt.String() + " as type " + elem.String() + " in " + op)
}
slice.Index(i).Set(x)
}
origIn := in
in = make([]Value, n+1)
copy(in[:n], origIn)
in[n] = slice
}
nin := len(in)
if nin != t.NumIn() {
panic("reflect.Value.Call: wrong argument count")
}
nout := t.NumOut()
// Register argument space.
var regArgs abi.RegArgs
// Compute frame type.
frametype, framePool, abid := funcLayout(t, rcvrtype)
// Allocate a chunk of memory for frame if needed.
var stackArgs unsafe.Pointer
if frametype.size != 0 {
if nout == 0 {
stackArgs = framePool.Get().(unsafe.Pointer)
} else {
// Can't use pool if the function has return values.
// We will leak pointer to args in ret, so its lifetime is not scoped.
stackArgs = unsafe_New(frametype)
}
}
frameSize := frametype.size
if debugReflectCall {
println("reflect.call", t.String())
abid.dump()
}
// Copy inputs into args.
// Handle receiver.
inStart := 0
if rcvrtype != nil {
// Guaranteed to only be one word in size,
// so it will only take up exactly 1 abiStep (either
// in a register or on the stack).
switch st := abid.call.steps[0]; st.kind {
case abiStepStack:
storeRcvr(rcvr, stackArgs)
case abiStepPointer:
storeRcvr(rcvr, unsafe.Pointer(®Args.Ptrs[st.ireg]))
fallthrough
case abiStepIntReg:
storeRcvr(rcvr, unsafe.Pointer(®Args.Ints[st.ireg]))
case abiStepFloatReg:
storeRcvr(rcvr, unsafe.Pointer(®Args.Floats[st.freg]))
default:
panic("unknown ABI parameter kind")
}
inStart = 1
}
// Handle arguments.
for i, v := range in {
v.mustBeExported()
targ := t.In(i).(*rtype)
// TODO(mknyszek): Figure out if it's possible to get some
// scratch space for this assignment check. Previously, it
// was possible to use space in the argument frame.
v = v.assignTo("reflect.Value.Call", targ, nil)
stepsLoop:
for _, st := range abid.call.stepsForValue(i + inStart) {
switch st.kind {
case abiStepStack:
// Copy values to the "stack."
addr := add(stackArgs, st.stkOff, "precomputed stack arg offset")
if v.flag&flagIndir != 0 {
typedmemmove(targ, addr, v.ptr)
} else {
*(*unsafe.Pointer)(addr) = v.ptr
}
// There's only one step for a stack-allocated value.
break stepsLoop
case abiStepIntReg, abiStepPointer:
// Copy values to "integer registers."
if v.flag&flagIndir != 0 {
offset := add(v.ptr, st.offset, "precomputed value offset")
if st.kind == abiStepPointer {
// Duplicate this pointer in the pointer area of the
// register space. Otherwise, there's the potential for
// this to be the last reference to v.ptr.
regArgs.Ptrs[st.ireg] = *(*unsafe.Pointer)(offset)
}
intToReg(®Args, st.ireg, st.size, offset)
} else {
if st.kind == abiStepPointer {
// See the comment in abiStepPointer case above.
regArgs.Ptrs[st.ireg] = v.ptr
}
regArgs.Ints[st.ireg] = uintptr(v.ptr)
}
case abiStepFloatReg:
// Copy values to "float registers."
if v.flag&flagIndir == 0 {
panic("attempted to copy pointer to FP register")
}
offset := add(v.ptr, st.offset, "precomputed value offset")
floatToReg(®Args, st.freg, st.size, offset)
default:
panic("unknown ABI part kind")
}
}
}
// TODO(mknyszek): Remove this when we no longer have
// caller reserved spill space.
frameSize = align(frameSize, goarch.PtrSize)
frameSize += abid.spill
// Mark pointers in registers for the return path.
regArgs.ReturnIsPtr = abid.outRegPtrs
if debugReflectCall {
regArgs.Dump()
}
// For testing; see TestCallArgLive.
if callGC {
runtime.GC()
}
// Call.
call(frametype, fn, stackArgs, uint32(frametype.size), uint32(abid.retOffset), uint32(frameSize), ®Args)
// For testing; see TestCallMethodJump.
if callGC {
runtime.GC()
}
var ret []Value
if nout == 0 {
if stackArgs != nil {
typedmemclr(frametype, stackArgs)
framePool.Put(stackArgs)
}
} else {
if stackArgs != nil {
// Zero the now unused input area of args,
// because the Values returned by this function contain pointers to the args object,
// and will thus keep the args object alive indefinitely.
typedmemclrpartial(frametype, stackArgs, 0, abid.retOffset)
}
// Wrap Values around return values in args.
ret = make([]Value, nout)
for i := 0; i < nout; i++ {
tv := t.Out(i)
if tv.Size() == 0 {
// For zero-sized return value, args+off may point to the next object.
// In this case, return the zero value instead.
ret[i] = Zero(tv)
continue
}
steps := abid.ret.stepsForValue(i)
if st := steps[0]; st.kind == abiStepStack {
// This value is on the stack. If part of a value is stack
// allocated, the entire value is according to the ABI. So
// just make an indirection into the allocated frame.
fl := flagIndir | flag(tv.Kind())
ret[i] = Value{tv.common(), add(stackArgs, st.stkOff, "tv.Size() != 0"), fl}
// Note: this does introduce false sharing between results -
// if any result is live, they are all live.
// (And the space for the args is live as well, but as we've
// cleared that space it isn't as big a deal.)
continue
}
// Handle pointers passed in registers.
if !ifaceIndir(tv.common()) {
// Pointer-valued data gets put directly
// into v.ptr.
if steps[0].kind != abiStepPointer {
print("kind=", steps[0].kind, ", type=", tv.String(), "\n")
panic("mismatch between ABI description and types")
}
ret[i] = Value{tv.common(), regArgs.Ptrs[steps[0].ireg], flag(tv.Kind())}
continue
}
// All that's left is values passed in registers that we need to
// create space for and copy values back into.
//
// TODO(mknyszek): We make a new allocation for each register-allocated
// value, but previously we could always point into the heap-allocated
// stack frame. This is a regression that could be fixed by adding
// additional space to the allocated stack frame and storing the
// register-allocated return values into the allocated stack frame and
// referring there in the resulting Value.
s := unsafe_New(tv.common())
for _, st := range steps {
switch st.kind {
case abiStepIntReg:
offset := add(s, st.offset, "precomputed value offset")
intFromReg(®Args, st.ireg, st.size, offset)
case abiStepPointer:
s := add(s, st.offset, "precomputed value offset")
*((*unsafe.Pointer)(s)) = regArgs.Ptrs[st.ireg]
case abiStepFloatReg:
offset := add(s, st.offset, "precomputed value offset")
floatFromReg(®Args, st.freg, st.size, offset)
case abiStepStack:
panic("register-based return value has stack component")
default:
panic("unknown ABI part kind")
}
}
ret[i] = Value{tv.common(), s, flagIndir | flag(tv.Kind())}
}
}
return ret
}
// callReflect is the call implementation used by a function
// returned by MakeFunc. In many ways it is the opposite of the
// method Value.call above. The method above converts a call using Values
// into a call of a function with a concrete argument frame, while
// callReflect converts a call of a function with a concrete argument
// frame into a call using Values.
// It is in this file so that it can be next to the call method above.
// The remainder of the MakeFunc implementation is in makefunc.go.
//
// NOTE: This function must be marked as a "wrapper" in the generated code,
// so that the linker can make it work correctly for panic and recover.
// The gc compilers know to do that for the name "reflect.callReflect".
//
// ctxt is the "closure" generated by MakeFunc.
// frame is a pointer to the arguments to that closure on the stack.
// retValid points to a boolean which should be set when the results
// section of frame is set.
//
// regs contains the argument values passed in registers and will contain
// the values returned from ctxt.fn in registers.
func callReflect(ctxt *makeFuncImpl, frame unsafe.Pointer, retValid *bool, regs *abi.RegArgs) {
if callGC {
// Call GC upon entry during testing.
// Getting our stack scanned here is the biggest hazard, because
// our caller (makeFuncStub) could have failed to place the last
// pointer to a value in regs' pointer space, in which case it
// won't be visible to the GC.
runtime.GC()
}
ftyp := ctxt.ftyp
f := ctxt.fn
_, _, abid := funcLayout(ftyp, nil)
// Copy arguments into Values.
ptr := frame
in := make([]Value, 0, int(ftyp.inCount))
for i, typ := range ftyp.in() {
if typ.Size() == 0 {
in = append(in, Zero(typ))
continue
}
v := Value{typ, nil, flag(typ.Kind())}
steps := abid.call.stepsForValue(i)
if st := steps[0]; st.kind == abiStepStack {
if ifaceIndir(typ) {
// value cannot be inlined in interface data.
// Must make a copy, because f might keep a reference to it,
// and we cannot let f keep a reference to the stack frame
// after this function returns, not even a read-only reference.
v.ptr = unsafe_New(typ)
if typ.size > 0 {
typedmemmove(typ, v.ptr, add(ptr, st.stkOff, "typ.size > 0"))
}
v.flag |= flagIndir
} else {
v.ptr = *(*unsafe.Pointer)(add(ptr, st.stkOff, "1-ptr"))
}
} else {
if ifaceIndir(typ) {
// All that's left is values passed in registers that we need to
// create space for the values.
v.flag |= flagIndir
v.ptr = unsafe_New(typ)
for _, st := range steps {
switch st.kind {
case abiStepIntReg:
offset := add(v.ptr, st.offset, "precomputed value offset")
intFromReg(regs, st.ireg, st.size, offset)
case abiStepPointer:
s := add(v.ptr, st.offset, "precomputed value offset")
*((*unsafe.Pointer)(s)) = regs.Ptrs[st.ireg]
case abiStepFloatReg:
offset := add(v.ptr, st.offset, "precomputed value offset")
floatFromReg(regs, st.freg, st.size, offset)
case abiStepStack:
panic("register-based return value has stack component")
default:
panic("unknown ABI part kind")
}
}
} else {
// Pointer-valued data gets put directly
// into v.ptr.
if steps[0].kind != abiStepPointer {
print("kind=", steps[0].kind, ", type=", typ.String(), "\n")
panic("mismatch between ABI description and types")
}
v.ptr = regs.Ptrs[steps[0].ireg]
}
}
in = append(in, v)
}
// Call underlying function.
out := f(in)
numOut := ftyp.NumOut()
if len(out) != numOut {
panic("reflect: wrong return count from function created by MakeFunc")
}
// Copy results back into argument frame and register space.
if numOut > 0 {
for i, typ := range ftyp.out() {
v := out[i]
if v.typ == nil {
panic("reflect: function created by MakeFunc using " + funcName(f) +
" returned zero Value")
}
if v.flag&flagRO != 0 {
panic("reflect: function created by MakeFunc using " + funcName(f) +
" returned value obtained from unexported field")
}
if typ.size == 0 {
continue
}
// Convert v to type typ if v is assignable to a variable
// of type t in the language spec.
// See issue 28761.
//
//
// TODO(mknyszek): In the switch to the register ABI we lost
// the scratch space here for the register cases (and
// temporarily for all the cases).
//
// If/when this happens, take note of the following:
//
// We must clear the destination before calling assignTo,
// in case assignTo writes (with memory barriers) to the
// target location used as scratch space. See issue 39541.
v = v.assignTo("reflect.MakeFunc", typ, nil)
stepsLoop:
for _, st := range abid.ret.stepsForValue(i) {
switch st.kind {
case abiStepStack:
// Copy values to the "stack."
addr := add(ptr, st.stkOff, "precomputed stack arg offset")
// Do not use write barriers. The stack space used
// for this call is not adequately zeroed, and we
// are careful to keep the arguments alive until we
// return to makeFuncStub's caller.
if v.flag&flagIndir != 0 {
memmove(addr, v.ptr, st.size)
} else {
// This case must be a pointer type.
*(*uintptr)(addr) = uintptr(v.ptr)
}
// There's only one step for a stack-allocated value.
break stepsLoop
case abiStepIntReg, abiStepPointer:
// Copy values to "integer registers."
if v.flag&flagIndir != 0 {
offset := add(v.ptr, st.offset, "precomputed value offset")
intToReg(regs, st.ireg, st.size, offset)
} else {
// Only populate the Ints space on the return path.
// This is safe because out is kept alive until the
// end of this function, and the return path through
// makeFuncStub has no preemption, so these pointers
// are always visible to the GC.
regs.Ints[st.ireg] = uintptr(v.ptr)
}
case abiStepFloatReg:
// Copy values to "float registers."
if v.flag&flagIndir == 0 {
panic("attempted to copy pointer to FP register")
}
offset := add(v.ptr, st.offset, "precomputed value offset")
floatToReg(regs, st.freg, st.size, offset)
default:
panic("unknown ABI part kind")
}
}
}
}
// Announce that the return values are valid.
// After this point the runtime can depend on the return values being valid.
*retValid = true
// We have to make sure that the out slice lives at least until
// the runtime knows the return values are valid. Otherwise, the
// return values might not be scanned by anyone during a GC.
// (out would be dead, and the return slots not yet alive.)
runtime.KeepAlive(out)
// runtime.getArgInfo expects to be able to find ctxt on the
// stack when it finds our caller, makeFuncStub. Make sure it
// doesn't get garbage collected.
runtime.KeepAlive(ctxt)
}
// methodReceiver returns information about the receiver
// described by v. The Value v may or may not have the
// flagMethod bit set, so the kind cached in v.flag should
// not be used.
// The return value rcvrtype gives the method's actual receiver type.
// The return value t gives the method type signature (without the receiver).
// The return value fn is a pointer to the method code.
func methodReceiver(op string, v Value, methodIndex int) (rcvrtype *rtype, t *funcType, fn unsafe.Pointer) {
i := methodIndex
if v.typ.Kind() == Interface {
tt := (*interfaceType)(unsafe.Pointer(v.typ))
if uint(i) >= uint(len(tt.methods)) {
panic("reflect: internal error: invalid method index")
}
m := &tt.methods[i]
if !tt.nameOff(m.name).isExported() {
panic("reflect: " + op + " of unexported method")
}
iface := (*nonEmptyInterface)(v.ptr)
if iface.itab == nil {
panic("reflect: " + op + " of method on nil interface value")
}
rcvrtype = iface.itab.typ
fn = unsafe.Pointer(&iface.itab.fun[i])
t = (*funcType)(unsafe.Pointer(tt.typeOff(m.typ)))
} else {
rcvrtype = v.typ
ms := v.typ.exportedMethods()
if uint(i) >= uint(len(ms)) {
panic("reflect: internal error: invalid method index")
}
m := ms[i]
if !v.typ.nameOff(m.name).isExported() {
panic("reflect: " + op + " of unexported method")
}
ifn := v.typ.textOff(m.ifn)
fn = unsafe.Pointer(&ifn)
t = (*funcType)(unsafe.Pointer(v.typ.typeOff(m.mtyp)))
}
return
}
// v is a method receiver. Store at p the word which is used to
// encode that receiver at the start of the argument list.
// Reflect uses the "interface" calling convention for
// methods, which always uses one word to record the receiver.
func storeRcvr(v Value, p unsafe.Pointer) {
t := v.typ
if t.Kind() == Interface {
// the interface data word becomes the receiver word
iface := (*nonEmptyInterface)(v.ptr)
*(*unsafe.Pointer)(p) = iface.word
} else if v.flag&flagIndir != 0 && !ifaceIndir(t) {
*(*unsafe.Pointer)(p) = *(*unsafe.Pointer)(v.ptr)
} else {
*(*unsafe.Pointer)(p) = v.ptr
}
}
// align returns the result of rounding x up to a multiple of n.
// n must be a power of two.
func align(x, n uintptr) uintptr {
return (x + n - 1) &^ (n - 1)
}
// callMethod is the call implementation used by a function returned
// by makeMethodValue (used by v.Method(i).Interface()).
// It is a streamlined version of the usual reflect call: the caller has
// already laid out the argument frame for us, so we don't have
// to deal with individual Values for each argument.
// It is in this file so that it can be next to the two similar functions above.
// The remainder of the makeMethodValue implementation is in makefunc.go.
//
// NOTE: This function must be marked as a "wrapper" in the generated code,
// so that the linker can make it work correctly for panic and recover.
// The gc compilers know to do that for the name "reflect.callMethod".
//
// ctxt is the "closure" generated by makeVethodValue.
// frame is a pointer to the arguments to that closure on the stack.
// retValid points to a boolean which should be set when the results
// section of frame is set.
//
// regs contains the argument values passed in registers and will contain
// the values returned from ctxt.fn in registers.
func callMethod(ctxt *methodValue, frame unsafe.Pointer, retValid *bool, regs *abi.RegArgs) {
rcvr := ctxt.rcvr
rcvrType, valueFuncType, methodFn := methodReceiver("call", rcvr, ctxt.method)
// There are two ABIs at play here.
//
// methodValueCall was invoked with the ABI assuming there was no
// receiver ("value ABI") and that's what frame and regs are holding.
//
// Meanwhile, we need to actually call the method with a receiver, which
// has its own ABI ("method ABI"). Everything that follows is a translation
// between the two.
_, _, valueABI := funcLayout(valueFuncType, nil)
valueFrame, valueRegs := frame, regs
methodFrameType, methodFramePool, methodABI := funcLayout(valueFuncType, rcvrType)
// Make a new frame that is one word bigger so we can store the receiver.
// This space is used for both arguments and return values.
methodFrame := methodFramePool.Get().(unsafe.Pointer)
var methodRegs abi.RegArgs
// Deal with the receiver. It's guaranteed to only be one word in size.
switch st := methodABI.call.steps[0]; st.kind {
case abiStepStack:
// Only copy the receiver to the stack if the ABI says so.
// Otherwise, it'll be in a register already.
storeRcvr(rcvr, methodFrame)
case abiStepPointer:
// Put the receiver in a register.
storeRcvr(rcvr, unsafe.Pointer(&methodRegs.Ptrs[st.ireg]))
fallthrough
case abiStepIntReg:
storeRcvr(rcvr, unsafe.Pointer(&methodRegs.Ints[st.ireg]))
case abiStepFloatReg:
storeRcvr(rcvr, unsafe.Pointer(&methodRegs.Floats[st.freg]))
default:
panic("unknown ABI parameter kind")
}
// Translate the rest of the arguments.
for i, t := range valueFuncType.in() {
valueSteps := valueABI.call.stepsForValue(i)
methodSteps := methodABI.call.stepsForValue(i + 1)
// Zero-sized types are trivial: nothing to do.
if len(valueSteps) == 0 {
if len(methodSteps) != 0 {
panic("method ABI and value ABI do not align")
}
continue
}
// There are four cases to handle in translating each
// argument:
// 1. Stack -> stack translation.
// 2. Stack -> registers translation.
// 3. Registers -> stack translation.
// 4. Registers -> registers translation.
// If the value ABI passes the value on the stack,
// then the method ABI does too, because it has strictly
// fewer arguments. Simply copy between the two.
if vStep := valueSteps[0]; vStep.kind == abiStepStack {
mStep := methodSteps[0]
// Handle stack -> stack translation.
if mStep.kind == abiStepStack {
if vStep.size != mStep.size {
panic("method ABI and value ABI do not align")
}
typedmemmove(t,
add(methodFrame, mStep.stkOff, "precomputed stack offset"),
add(valueFrame, vStep.stkOff, "precomputed stack offset"))
continue
}
// Handle stack -> register translation.
for _, mStep := range methodSteps {
from := add(valueFrame, vStep.stkOff+mStep.offset, "precomputed stack offset")
switch mStep.kind {
case abiStepPointer:
// Do the pointer copy directly so we get a write barrier.
methodRegs.Ptrs[mStep.ireg] = *(*unsafe.Pointer)(from)
fallthrough // We need to make sure this ends up in Ints, too.
case abiStepIntReg:
intToReg(&methodRegs, mStep.ireg, mStep.size, from)
case abiStepFloatReg:
floatToReg(&methodRegs, mStep.freg, mStep.size, from)
default:
panic("unexpected method step")
}
}
continue
}
// Handle register -> stack translation.
if mStep := methodSteps[0]; mStep.kind == abiStepStack {
for _, vStep := range valueSteps {
to := add(methodFrame, mStep.stkOff+vStep.offset, "precomputed stack offset")
switch vStep.kind {
case abiStepPointer:
// Do the pointer copy directly so we get a write barrier.
*(*unsafe.Pointer)(to) = valueRegs.Ptrs[vStep.ireg]
case abiStepIntReg:
intFromReg(valueRegs, vStep.ireg, vStep.size, to)
case abiStepFloatReg:
floatFromReg(valueRegs, vStep.freg, vStep.size, to)
default:
panic("unexpected value step")
}
}
continue
}
// Handle register -> register translation.
if len(valueSteps) != len(methodSteps) {
// Because it's the same type for the value, and it's assigned
// to registers both times, it should always take up the same
// number of registers for each ABI.
panic("method ABI and value ABI don't align")
}
for i, vStep := range valueSteps {
mStep := methodSteps[i]
if mStep.kind != vStep.kind {
panic("method ABI and value ABI don't align")
}
switch vStep.kind {
case abiStepPointer:
// Copy this too, so we get a write barrier.
methodRegs.Ptrs[mStep.ireg] = valueRegs.Ptrs[vStep.ireg]
fallthrough
case abiStepIntReg:
methodRegs.Ints[mStep.ireg] = valueRegs.Ints[vStep.ireg]
case abiStepFloatReg:
methodRegs.Floats[mStep.freg] = valueRegs.Floats[vStep.freg]
default:
panic("unexpected value step")
}
}
}
methodFrameSize := methodFrameType.size
// TODO(mknyszek): Remove this when we no longer have
// caller reserved spill space.
methodFrameSize = align(methodFrameSize, goarch.PtrSize)
methodFrameSize += methodABI.spill
// Mark pointers in registers for the return path.
methodRegs.ReturnIsPtr = methodABI.outRegPtrs
// Call.
// Call copies the arguments from scratch to the stack, calls fn,
// and then copies the results back into scratch.
call(methodFrameType, methodFn, methodFrame, uint32(methodFrameType.size), uint32(methodABI.retOffset), uint32(methodFrameSize), &methodRegs)
// Copy return values.
//
// This is somewhat simpler because both ABIs have an identical
// return value ABI (the types are identical). As a result, register
// results can simply be copied over. Stack-allocated values are laid
// out the same, but are at different offsets from the start of the frame
// Ignore any changes to args.
// Avoid constructing out-of-bounds pointers if there are no return values.
// because the arguments may be laid out differently.
if valueRegs != nil {
*valueRegs = methodRegs
}
if retSize := methodFrameType.size - methodABI.retOffset; retSize > 0 {
valueRet := add(valueFrame, valueABI.retOffset, "valueFrame's size > retOffset")
methodRet := add(methodFrame, methodABI.retOffset, "methodFrame's size > retOffset")
// This copies to the stack. Write barriers are not needed.
memmove(valueRet, methodRet, retSize)
}
// Tell the runtime it can now depend on the return values
// being properly initialized.
*retValid = true
// Clear the scratch space and put it back in the pool.
// This must happen after the statement above, so that the return
// values will always be scanned by someone.
typedmemclr(methodFrameType, methodFrame)
methodFramePool.Put(methodFrame)
// See the comment in callReflect.
runtime.KeepAlive(ctxt)
// Keep valueRegs alive because it may hold live pointer results.
// The caller (methodValueCall) has it as a stack object, which is only
// scanned when there is a reference to it.
runtime.KeepAlive(valueRegs)
}
// funcName returns the name of f, for use in error messages.
func funcName(f func([]Value) []Value) string {
pc := *(*uintptr)(unsafe.Pointer(&f))
rf := runtime.FuncForPC(pc)
if rf != nil {
return rf.Name()
}
return "closure"
}
// Cap returns v's capacity.
// It panics if v's Kind is not Array, Chan, Slice or pointer to Array.
func (v Value) Cap() int {
// capNonSlice is split out to keep Cap inlineable for slice kinds.
if v.kind() == Slice {
return (*unsafeheader.Slice)(v.ptr).Cap
}
return v.capNonSlice()
}
func (v Value) capNonSlice() int {
k := v.kind()
switch k {
case Array:
return v.typ.Len()
case Chan:
return chancap(v.pointer())
case Ptr:
if v.typ.Elem().Kind() == Array {
return v.typ.Elem().Len()
}
panic("reflect: call of reflect.Value.Cap on ptr to non-array Value")
}
panic(&ValueError{"reflect.Value.Cap", v.kind()})
}
// Close closes the channel v.
// It panics if v's Kind is not Chan.
func (v Value) Close() {
v.mustBe(Chan)
v.mustBeExported()
chanclose(v.pointer())
}
// CanComplex reports whether Complex can be used without panicking.
func (v Value) CanComplex() bool {
switch v.kind() {
case Complex64, Complex128:
return true
default:
return false
}
}
// Complex returns v's underlying value, as a complex128.
// It panics if v's Kind is not Complex64 or Complex128
func (v Value) Complex() complex128 {
k := v.kind()
switch k {
case Complex64:
return complex128(*(*complex64)(v.ptr))
case Complex128:
return *(*complex128)(v.ptr)
}
panic(&ValueError{"reflect.Value.Complex", v.kind()})
}
// Elem returns the value that the interface v contains
// or that the pointer v points to.
// It panics if v's Kind is not Interface or Pointer.
// It returns the zero Value if v is nil.
func (v Value) Elem() Value {
k := v.kind()
switch k {
case Interface:
var eface any
if v.typ.NumMethod() == 0 {
eface = *(*any)(v.ptr)
} else {
eface = (any)(*(*interface {
M()
})(v.ptr))
}
x := unpackEface(eface)
if x.flag != 0 {
x.flag |= v.flag.ro()
}
return x
case Pointer:
ptr := v.ptr
if v.flag&flagIndir != 0 {
if ifaceIndir(v.typ) {
// This is a pointer to a not-in-heap object. ptr points to a uintptr
// in the heap. That uintptr is the address of a not-in-heap object.
// In general, pointers to not-in-heap objects can be total junk.
// But Elem() is asking to dereference it, so the user has asserted
// that at least it is a valid pointer (not just an integer stored in
// a pointer slot). So let's check, to make sure that it isn't a pointer
// that the runtime will crash on if it sees it during GC or write barriers.
// Since it is a not-in-heap pointer, all pointers to the heap are
// forbidden! That makes the test pretty easy.
// See issue 48399.
if !verifyNotInHeapPtr(*(*uintptr)(ptr)) {
panic("reflect: reflect.Value.Elem on an invalid notinheap pointer")
}
}
ptr = *(*unsafe.Pointer)(ptr)
}
// The returned value's address is v's value.
if ptr == nil {
return Value{}
}
tt := (*ptrType)(unsafe.Pointer(v.typ))
typ := tt.elem
fl := v.flag&flagRO | flagIndir | flagAddr
fl |= flag(typ.Kind())
return Value{typ, ptr, fl}
}
panic(&ValueError{"reflect.Value.Elem", v.kind()})
}
// Field returns the i'th field of the struct v.
// It panics if v's Kind is not Struct or i is out of range.
func (v Value) Field(i int) Value {
if v.kind() != Struct {
panic(&ValueError{"reflect.Value.Field", v.kind()})
}
tt := (*structType)(unsafe.Pointer(v.typ))
if uint(i) >= uint(len(tt.fields)) {
panic("reflect: Field index out of range")
}
field := &tt.fields[i]
typ := field.typ
// Inherit permission bits from v, but clear flagEmbedRO.
fl := v.flag&(flagStickyRO|flagIndir|flagAddr) | flag(typ.Kind())
// Using an unexported field forces flagRO.
if !field.name.isExported() {
if field.embedded() {
fl |= flagEmbedRO
} else {
fl |= flagStickyRO
}
}
// Either flagIndir is set and v.ptr points at struct,
// or flagIndir is not set and v.ptr is the actual struct data.
// In the former case, we want v.ptr + offset.
// In the latter case, we must have field.offset = 0,
// so v.ptr + field.offset is still the correct address.
ptr := add(v.ptr, field.offset, "same as non-reflect &v.field")
return Value{typ, ptr, fl}
}
// FieldByIndex returns the nested field corresponding to index.
// It panics if evaluation requires stepping through a nil
// pointer or a field that is not a struct.
func (v Value) FieldByIndex(index []int) Value {
if len(index) == 1 {
return v.Field(index[0])
}
v.mustBe(Struct)
for i, x := range index {
if i > 0 {
if v.Kind() == Pointer && v.typ.Elem().Kind() == Struct {
if v.IsNil() {
panic("reflect: indirection through nil pointer to embedded struct")
}
v = v.Elem()
}
}
v = v.Field(x)
}
return v
}
// FieldByIndexErr returns the nested field corresponding to index.
// It returns an error if evaluation requires stepping through a nil
// pointer, but panics if it must step through a field that
// is not a struct.
func (v Value) FieldByIndexErr(index []int) (Value, error) {
if len(index) == 1 {
return v.Field(index[0]), nil
}
v.mustBe(Struct)
for i, x := range index {
if i > 0 {
if v.Kind() == Ptr && v.typ.Elem().Kind() == Struct {
if v.IsNil() {
return Value{}, errors.New("reflect: indirection through nil pointer to embedded struct field " + v.typ.Elem().Name())
}
v = v.Elem()
}
}
v = v.Field(x)
}
return v, nil
}
// FieldByName returns the struct field with the given name.
// It returns the zero Value if no field was found.
// It panics if v's Kind is not struct.
func (v Value) FieldByName(name string) Value {
v.mustBe(Struct)
if f, ok := v.typ.FieldByName(name); ok {
return v.FieldByIndex(f.Index)
}
return Value{}
}
// FieldByNameFunc returns the struct field with a name
// that satisfies the match function.
// It panics if v's Kind is not struct.
// It returns the zero Value if no field was found.
func (v Value) FieldByNameFunc(match func(string) bool) Value {
if f, ok := v.typ.FieldByNameFunc(match); ok {
return v.FieldByIndex(f.Index)
}
return Value{}
}
// CanFloat reports whether Float can be used without panicking.
func (v Value) CanFloat() bool {
switch v.kind() {
case Float32, Float64:
return true
default:
return false
}
}
// Float returns v's underlying value, as a float64.
// It panics if v's Kind is not Float32 or Float64
func (v Value) Float() float64 {
k := v.kind()
switch k {
case Float32:
return float64(*(*float32)(v.ptr))
case Float64:
return *(*float64)(v.ptr)
}
panic(&ValueError{"reflect.Value.Float", v.kind()})
}
var uint8Type = TypeOf(uint8(0)).(*rtype)
// Index returns v's i'th element.
// It panics if v's Kind is not Array, Slice, or String or i is out of range.
func (v Value) Index(i int) Value {
switch v.kind() {
case Array:
tt := (*arrayType)(unsafe.Pointer(v.typ))
if uint(i) >= uint(tt.len) {
panic("reflect: array index out of range")
}
typ := tt.elem
offset := uintptr(i) * typ.size
// Either flagIndir is set and v.ptr points at array,
// or flagIndir is not set and v.ptr is the actual array data.
// In the former case, we want v.ptr + offset.
// In the latter case, we must be doing Index(0), so offset = 0,
// so v.ptr + offset is still the correct address.
val := add(v.ptr, offset, "same as &v[i], i < tt.len")
fl := v.flag&(flagIndir|flagAddr) | v.flag.ro() | flag(typ.Kind()) // bits same as overall array
return Value{typ, val, fl}
case Slice:
// Element flag same as Elem of Pointer.
// Addressable, indirect, possibly read-only.
s := (*unsafeheader.Slice)(v.ptr)
if uint(i) >= uint(s.Len) {
panic("reflect: slice index out of range")
}
tt := (*sliceType)(unsafe.Pointer(v.typ))
typ := tt.elem
val := arrayAt(s.Data, i, typ.size, "i < s.Len")
fl := flagAddr | flagIndir | v.flag.ro() | flag(typ.Kind())
return Value{typ, val, fl}
case String:
s := (*unsafeheader.String)(v.ptr)
if uint(i) >= uint(s.Len) {
panic("reflect: string index out of range")
}
p := arrayAt(s.Data, i, 1, "i < s.Len")
fl := v.flag.ro() | flag(Uint8) | flagIndir
return Value{uint8Type, p, fl}
}
panic(&ValueError{"reflect.Value.Index", v.kind()})
}
// CanInt reports whether Int can be used without panicking.
func (v Value) CanInt() bool {
switch v.kind() {
case Int, Int8, Int16, Int32, Int64:
return true
default:
return false
}
}
// Int returns v's underlying value, as an int64.
// It panics if v's Kind is not Int, Int8, Int16, Int32, or Int64.
func (v Value) Int() int64 {
k := v.kind()
p := v.ptr
switch k {
case Int:
return int64(*(*int)(p))
case Int8:
return int64(*(*int8)(p))
case Int16:
return int64(*(*int16)(p))
case Int32:
return int64(*(*int32)(p))
case Int64:
return *(*int64)(p)
}
panic(&ValueError{"reflect.Value.Int", v.kind()})
}
// CanInterface reports whether Interface can be used without panicking.
func (v Value) CanInterface() bool {
if v.flag == 0 {
panic(&ValueError{"reflect.Value.CanInterface", Invalid})
}
return v.flag&flagRO == 0
}
// Interface returns v's current value as an interface{}.
// It is equivalent to:
//
// var i interface{} = (v's underlying value)
//
// It panics if the Value was obtained by accessing
// unexported struct fields.
func (v Value) Interface() (i any) {
return valueInterface(v, true)
}
func valueInterface(v Value, safe bool) any {
if v.flag == 0 {
panic(&ValueError{"reflect.Value.Interface", Invalid})
}
if safe && v.flag&flagRO != 0 {
// Do not allow access to unexported values via Interface,
// because they might be pointers that should not be
// writable or methods or function that should not be callable.
panic("reflect.Value.Interface: cannot return value obtained from unexported field or method")
}
if v.flag&flagMethod != 0 {
v = makeMethodValue("Interface", v)
}
if v.kind() == Interface {
// Special case: return the element inside the interface.
// Empty interface has one layout, all interfaces with
// methods have a second layout.
if v.NumMethod() == 0 {
return *(*any)(v.ptr)
}
return *(*interface {
M()
})(v.ptr)
}
// TODO: pass safe to packEface so we don't need to copy if safe==true?
return packEface(v)
}
// InterfaceData returns a pair of unspecified uintptr values.
// It panics if v's Kind is not Interface.
//
// In earlier versions of Go, this function returned the interface's
// value as a uintptr pair. As of Go 1.4, the implementation of
// interface values precludes any defined use of InterfaceData.
//
// Deprecated: The memory representation of interface values is not
// compatible with InterfaceData.
func (v Value) InterfaceData() [2]uintptr {
v.mustBe(Interface)
// We treat this as a read operation, so we allow
// it even for unexported data, because the caller
// has to import "unsafe" to turn it into something
// that can be abused.
// Interface value is always bigger than a word; assume flagIndir.
return *(*[2]uintptr)(v.ptr)
}
// IsNil reports whether its argument v is nil. The argument must be
// a chan, func, interface, map, pointer, or slice value; if it is
// not, IsNil panics. Note that IsNil is not always equivalent to a
// regular comparison with nil in Go. For example, if v was created
// by calling ValueOf with an uninitialized interface variable i,
// i==nil will be true but v.IsNil will panic as v will be the zero
// Value.
func (v Value) IsNil() bool {
k := v.kind()
switch k {
case Chan, Func, Map, Pointer, UnsafePointer:
if v.flag&flagMethod != 0 {
return false
}
ptr := v.ptr
if v.flag&flagIndir != 0 {
ptr = *(*unsafe.Pointer)(ptr)
}
return ptr == nil
case Interface, Slice:
// Both interface and slice are nil if first word is 0.
// Both are always bigger than a word; assume flagIndir.
return *(*unsafe.Pointer)(v.ptr) == nil
}
panic(&ValueError{"reflect.Value.IsNil", v.kind()})
}
// IsValid reports whether v represents a value.
// It returns false if v is the zero Value.
// If IsValid returns false, all other methods except String panic.
// Most functions and methods never return an invalid Value.
// If one does, its documentation states the conditions explicitly.
func (v Value) IsValid() bool {
return v.flag != 0
}
// IsZero reports whether v is the zero value for its type.
// It panics if the argument is invalid.
func (v Value) IsZero() bool {
switch v.kind() {
case Bool:
return !v.Bool()
case Int, Int8, Int16, Int32, Int64:
return v.Int() == 0
case Uint, Uint8, Uint16, Uint32, Uint64, Uintptr:
return v.Uint() == 0
case Float32, Float64:
return math.Float64bits(v.Float()) == 0
case Complex64, Complex128:
c := v.Complex()
return math.Float64bits(real(c)) == 0 && math.Float64bits(imag(c)) == 0
case Array:
for i := 0; i < v.Len(); i++ {
if !v.Index(i).IsZero() {
return false
}
}
return true
case Chan, Func, Interface, Map, Pointer, Slice, UnsafePointer:
return v.IsNil()
case String:
return v.Len() == 0
case Struct:
for i := 0; i < v.NumField(); i++ {
if !v.Field(i).IsZero() {
return false
}
}
return true
default:
// This should never happens, but will act as a safeguard for
// later, as a default value doesn't makes sense here.
panic(&ValueError{"reflect.Value.IsZero", v.Kind()})
}
}
// Kind returns v's Kind.
// If v is the zero Value (IsValid returns false), Kind returns Invalid.
func (v Value) Kind() Kind {
return v.kind()
}
// Len returns v's length.
// It panics if v's Kind is not Array, Chan, Map, Slice, String, or pointer to Array.
func (v Value) Len() int {
// lenNonSlice is split out to keep Len inlineable for slice kinds.
if v.kind() == Slice {
return (*unsafeheader.Slice)(v.ptr).Len
}
return v.lenNonSlice()
}
func (v Value) lenNonSlice() int {
switch k := v.kind(); k {
case Array:
tt := (*arrayType)(unsafe.Pointer(v.typ))
return int(tt.len)
case Chan:
return chanlen(v.pointer())
case Map:
return maplen(v.pointer())
case String:
// String is bigger than a word; assume flagIndir.
return (*unsafeheader.String)(v.ptr).Len
case Ptr:
if v.typ.Elem().Kind() == Array {
return v.typ.Elem().Len()
}
panic("reflect: call of reflect.Value.Len on ptr to non-array Value")
}
panic(&ValueError{"reflect.Value.Len", v.kind()})
}
var stringType = TypeOf("").(*rtype)
// MapIndex returns the value associated with key in the map v.
// It panics if v's Kind is not Map.
// It returns the zero Value if key is not found in the map or if v represents a nil map.
// As in Go, the key's value must be assignable to the map's key type.
func (v Value) MapIndex(key Value) Value {
v.mustBe(Map)
tt := (*mapType)(unsafe.Pointer(v.typ))
// Do not require key to be exported, so that DeepEqual
// and other programs can use all the keys returned by
// MapKeys as arguments to MapIndex. If either the map
// or the key is unexported, though, the result will be
// considered unexported. This is consistent with the
// behavior for structs, which allow read but not write
// of unexported fields.
var e unsafe.Pointer
if (tt.key == stringType || key.kind() == String) && tt.key == key.typ && tt.elem.size <= maxValSize {
k := *(*string)(key.ptr)
e = mapaccess_faststr(v.typ, v.pointer(), k)
} else {
key = key.assignTo("reflect.Value.MapIndex", tt.key, nil)
var k unsafe.Pointer
if key.flag&flagIndir != 0 {
k = key.ptr
} else {
k = unsafe.Pointer(&key.ptr)
}
e = mapaccess(v.typ, v.pointer(), k)
}
if e == nil {
return Value{}
}
typ := tt.elem
fl := (v.flag | key.flag).ro()
fl |= flag(typ.Kind())
return copyVal(typ, fl, e)
}
// MapKeys returns a slice containing all the keys present in the map,
// in unspecified order.
// It panics if v's Kind is not Map.
// It returns an empty slice if v represents a nil map.
func (v Value) MapKeys() []Value {
v.mustBe(Map)
tt := (*mapType)(unsafe.Pointer(v.typ))
keyType := tt.key
fl := v.flag.ro() | flag(keyType.Kind())
m := v.pointer()
mlen := int(0)
if m != nil {
mlen = maplen(m)
}
var it hiter
mapiterinit(v.typ, m, &it)
a := make([]Value, mlen)
var i int
for i = 0; i < len(a); i++ {
key := mapiterkey(&it)
if key == nil {
// Someone deleted an entry from the map since we
// called maplen above. It's a data race, but nothing
// we can do about it.
break
}
a[i] = copyVal(keyType, fl, key)
mapiternext(&it)
}
return a[:i]
}
// hiter's structure matches runtime.hiter's structure.
// Having a clone here allows us to embed a map iterator
// inside type MapIter so that MapIters can be re-used
// without doing any allocations.
type hiter struct {
key unsafe.Pointer
elem unsafe.Pointer
t unsafe.Pointer
h unsafe.Pointer
buckets unsafe.Pointer
bptr unsafe.Pointer
overflow *[]unsafe.Pointer
oldoverflow *[]unsafe.Pointer
startBucket uintptr
offset uint8
wrapped bool
B uint8
i uint8
bucket uintptr
checkBucket uintptr
}
func (h *hiter) initialized() bool {
return h.t != nil
}
// A MapIter is an iterator for ranging over a map.
// See Value.MapRange.
type MapIter struct {
m Value
hiter hiter
}
// Key returns the key of iter's current map entry.
func (iter *MapIter) Key() Value {
if !iter.hiter.initialized() {
panic("MapIter.Key called before Next")
}
iterkey := mapiterkey(&iter.hiter)
if iterkey == nil {
panic("MapIter.Key called on exhausted iterator")
}
t := (*mapType)(unsafe.Pointer(iter.m.typ))
ktype := t.key
return copyVal(ktype, iter.m.flag.ro()|flag(ktype.Kind()), iterkey)
}
// SetIterKey assigns to v the key of iter's current map entry.
// It is equivalent to v.Set(iter.Key()), but it avoids allocating a new Value.
// As in Go, the key must be assignable to v's type.
func (v Value) SetIterKey(iter *MapIter) {
if !iter.hiter.initialized() {
panic("reflect: Value.SetIterKey called before Next")
}
iterkey := mapiterkey(&iter.hiter)
if iterkey == nil {
panic("reflect: Value.SetIterKey called on exhausted iterator")
}
v.mustBeAssignable()
var target unsafe.Pointer
if v.kind() == Interface {
target = v.ptr
}
t := (*mapType)(unsafe.Pointer(iter.m.typ))
ktype := t.key
key := Value{ktype, iterkey, iter.m.flag | flag(ktype.Kind()) | flagIndir}
key = key.assignTo("reflect.MapIter.SetKey", v.typ, target)
typedmemmove(v.typ, v.ptr, key.ptr)
}
// Value returns the value of iter's current map entry.
func (iter *MapIter) Value() Value {
if !iter.hiter.initialized() {
panic("MapIter.Value called before Next")
}
iterelem := mapiterelem(&iter.hiter)
if iterelem == nil {
panic("MapIter.Value called on exhausted iterator")
}
t := (*mapType)(unsafe.Pointer(iter.m.typ))
vtype := t.elem
return copyVal(vtype, iter.m.flag.ro()|flag(vtype.Kind()), iterelem)
}
// SetIterValue assigns to v the value of iter's current map entry.
// It is equivalent to v.Set(iter.Value()), but it avoids allocating a new Value.
// As in Go, the value must be assignable to v's type.
func (v Value) SetIterValue(iter *MapIter) {
if !iter.hiter.initialized() {
panic("reflect: Value.SetIterValue called before Next")
}
iterelem := mapiterelem(&iter.hiter)
if iterelem == nil {
panic("reflect: Value.SetIterValue called on exhausted iterator")
}
v.mustBeAssignable()
var target unsafe.Pointer
if v.kind() == Interface {
target = v.ptr
}
t := (*mapType)(unsafe.Pointer(iter.m.typ))
vtype := t.elem
elem := Value{vtype, iterelem, iter.m.flag | flag(vtype.Kind()) | flagIndir}
elem = elem.assignTo("reflect.MapIter.SetValue", v.typ, target)
typedmemmove(v.typ, v.ptr, elem.ptr)
}
// Next advances the map iterator and reports whether there is another
// entry. It returns false when iter is exhausted; subsequent
// calls to Key, Value, or Next will panic.
func (iter *MapIter) Next() bool {
if !iter.m.IsValid() {
panic("MapIter.Next called on an iterator that does not have an associated map Value")
}
if !iter.hiter.initialized() {
mapiterinit(iter.m.typ, iter.m.pointer(), &iter.hiter)
} else {
if mapiterkey(&iter.hiter) == nil {
panic("MapIter.Next called on exhausted iterator")
}
mapiternext(&iter.hiter)
}
return mapiterkey(&iter.hiter) != nil
}
// Reset modifies iter to iterate over v.
// It panics if v's Kind is not Map and v is not the zero Value.
// Reset(Value{}) causes iter to not to refer to any map,
// which may allow the previously iterated-over map to be garbage collected.
func (iter *MapIter) Reset(v Value) {
if v.IsValid() {
v.mustBe(Map)
}
iter.m = v
iter.hiter = hiter{}
}
// MapRange returns a range iterator for a map.
// It panics if v's Kind is not Map.
//
// Call Next to advance the iterator, and Key/Value to access each entry.
// Next returns false when the iterator is exhausted.
// MapRange follows the same iteration semantics as a range statement.
//
// Example:
//
// iter := reflect.ValueOf(m).MapRange()
// for iter.Next() {
// k := iter.Key()
// v := iter.Value()
// ...
// }
func (v Value) MapRange() *MapIter {
// This is inlinable to take advantage of "function outlining".
// The allocation of MapIter can be stack allocated if the caller
// does not allow it to escape.
// See https://blog.filippo.io/efficient-go-apis-with-the-inliner/
if v.kind() != Map {
v.panicNotMap()
}
return &MapIter{m: v}
}
func (f flag) panicNotMap() {
f.mustBe(Map)
}
// copyVal returns a Value containing the map key or value at ptr,
// allocating a new variable as needed.
func copyVal(typ *rtype, fl flag, ptr unsafe.Pointer) Value {
if ifaceIndir(typ) {
// Copy result so future changes to the map
// won't change the underlying value.
c := unsafe_New(typ)
typedmemmove(typ, c, ptr)
return Value{typ, c, fl | flagIndir}
}
return Value{typ, *(*unsafe.Pointer)(ptr), fl}
}
// Method returns a function value corresponding to v's i'th method.
// The arguments to a Call on the returned function should not include
// a receiver; the returned function will always use v as the receiver.
// Method panics if i is out of range or if v is a nil interface value.
func (v Value) Method(i int) Value {
if v.typ == nil {
panic(&ValueError{"reflect.Value.Method", Invalid})
}
if v.flag&flagMethod != 0 || uint(i) >= uint(v.typ.NumMethod()) {
panic("reflect: Method index out of range")
}
if v.typ.Kind() == Interface && v.IsNil() {
panic("reflect: Method on nil interface value")
}
fl := v.flag.ro() | (v.flag & flagIndir)
fl |= flag(Func)
fl |= flag(i)<<flagMethodShift | flagMethod
return Value{v.typ, v.ptr, fl}
}
// NumMethod returns the number of methods in the value's method set.
//
// For a non-interface type, it returns the number of exported methods.
//
// For an interface type, it returns the number of exported and unexported methods.
func (v Value) NumMethod() int {
if v.typ == nil {
panic(&ValueError{"reflect.Value.NumMethod", Invalid})
}
if v.flag&flagMethod != 0 {
return 0
}
return v.typ.NumMethod()
}
// MethodByName returns a function value corresponding to the method
// of v with the given name.
// The arguments to a Call on the returned function should not include
// a receiver; the returned function will always use v as the receiver.
// It returns the zero Value if no method was found.
func (v Value) MethodByName(name string) Value {
if v.typ == nil {
panic(&ValueError{"reflect.Value.MethodByName", Invalid})
}
if v.flag&flagMethod != 0 {
return Value{}
}
m, ok := v.typ.MethodByName(name)
if !ok {
return Value{}
}
return v.Method(m.Index)
}
// NumField returns the number of fields in the struct v.
// It panics if v's Kind is not Struct.
func (v Value) NumField() int {
v.mustBe(Struct)
tt := (*structType)(unsafe.Pointer(v.typ))
return len(tt.fields)
}
// OverflowComplex reports whether the complex128 x cannot be represented by v's type.
// It panics if v's Kind is not Complex64 or Complex128.
func (v Value) OverflowComplex(x complex128) bool {
k := v.kind()
switch k {
case Complex64:
return overflowFloat32(real(x)) || overflowFloat32(imag(x))
case Complex128:
return false
}
panic(&ValueError{"reflect.Value.OverflowComplex", v.kind()})
}
// OverflowFloat reports whether the float64 x cannot be represented by v's type.
// It panics if v's Kind is not Float32 or Float64.
func (v Value) OverflowFloat(x float64) bool {
k := v.kind()
switch k {
case Float32:
return overflowFloat32(x)
case Float64:
return false
}
panic(&ValueError{"reflect.Value.OverflowFloat", v.kind()})
}
func overflowFloat32(x float64) bool {
if x < 0 {
x = -x
}
return math.MaxFloat32 < x && x <= math.MaxFloat64
}
// OverflowInt reports whether the int64 x cannot be represented by v's type.
// It panics if v's Kind is not Int, Int8, Int16, Int32, or Int64.
func (v Value) OverflowInt(x int64) bool {
k := v.kind()
switch k {
case Int, Int8, Int16, Int32, Int64:
bitSize := v.typ.size * 8
trunc := (x << (64 - bitSize)) >> (64 - bitSize)
return x != trunc
}
panic(&ValueError{"reflect.Value.OverflowInt", v.kind()})
}
// OverflowUint reports whether the uint64 x cannot be represented by v's type.
// It panics if v's Kind is not Uint, Uintptr, Uint8, Uint16, Uint32, or Uint64.
func (v Value) OverflowUint(x uint64) bool {
k := v.kind()
switch k {
case Uint, Uintptr, Uint8, Uint16, Uint32, Uint64:
bitSize := v.typ.size * 8
trunc := (x << (64 - bitSize)) >> (64 - bitSize)
return x != trunc
}
panic(&ValueError{"reflect.Value.OverflowUint", v.kind()})
}
//go:nocheckptr
// This prevents inlining Value.Pointer when -d=checkptr is enabled,
// which ensures cmd/compile can recognize unsafe.Pointer(v.Pointer())
// and make an exception.
// Pointer returns v's value as a uintptr.
// It returns uintptr instead of unsafe.Pointer so that
// code using reflect cannot obtain unsafe.Pointers
// without importing the unsafe package explicitly.
// It panics if v's Kind is not Chan, Func, Map, Pointer, Slice, or UnsafePointer.
//
// If v's Kind is Func, the returned pointer is an underlying
// code pointer, but not necessarily enough to identify a
// single function uniquely. The only guarantee is that the
// result is zero if and only if v is a nil func Value.
//
// If v's Kind is Slice, the returned pointer is to the first
// element of the slice. If the slice is nil the returned value
// is 0. If the slice is empty but non-nil the return value is non-zero.
//
// It's preferred to use uintptr(Value.UnsafePointer()) to get the equivalent result.
func (v Value) Pointer() uintptr {
k := v.kind()
switch k {
case Pointer:
if v.typ.ptrdata == 0 {
val := *(*uintptr)(v.ptr)
// Since it is a not-in-heap pointer, all pointers to the heap are
// forbidden! See comment in Value.Elem and issue #48399.
if !verifyNotInHeapPtr(val) {
panic("reflect: reflect.Value.Pointer on an invalid notinheap pointer")
}
return val
}
fallthrough
case Chan, Map, UnsafePointer:
return uintptr(v.pointer())
case Func:
if v.flag&flagMethod != 0 {
// As the doc comment says, the returned pointer is an
// underlying code pointer but not necessarily enough to
// identify a single function uniquely. All method expressions
// created via reflect have the same underlying code pointer,
// so their Pointers are equal. The function used here must
// match the one used in makeMethodValue.
return methodValueCallCodePtr()
}
p := v.pointer()
// Non-nil func value points at data block.
// First word of data block is actual code.
if p != nil {
p = *(*unsafe.Pointer)(p)
}
return uintptr(p)
case Slice:
return (*SliceHeader)(v.ptr).Data
}
panic(&ValueError{"reflect.Value.Pointer", v.kind()})
}
// Recv receives and returns a value from the channel v.
// It panics if v's Kind is not Chan.
// The receive blocks until a value is ready.
// The boolean value ok is true if the value x corresponds to a send
// on the channel, false if it is a zero value received because the channel is closed.
func (v Value) Recv() (x Value, ok bool) {
v.mustBe(Chan)
v.mustBeExported()
return v.recv(false)
}
// internal recv, possibly non-blocking (nb).
// v is known to be a channel.
func (v Value) recv(nb bool) (val Value, ok bool) {
tt := (*chanType)(unsafe.Pointer(v.typ))
if ChanDir(tt.dir)&RecvDir == 0 {
panic("reflect: recv on send-only channel")
}
t := tt.elem
val = Value{t, nil, flag(t.Kind())}
var p unsafe.Pointer
if ifaceIndir(t) {
p = unsafe_New(t)
val.ptr = p
val.flag |= flagIndir
} else {
p = unsafe.Pointer(&val.ptr)
}
selected, ok := chanrecv(v.pointer(), nb, p)
if !selected {
val = Value{}
}
return
}
// Send sends x on the channel v.
// It panics if v's kind is not Chan or if x's type is not the same type as v's element type.
// As in Go, x's value must be assignable to the channel's element type.
func (v Value) Send(x Value) {
v.mustBe(Chan)
v.mustBeExported()
v.send(x, false)
}
// internal send, possibly non-blocking.
// v is known to be a channel.
func (v Value) send(x Value, nb bool) (selected bool) {
tt := (*chanType)(unsafe.Pointer(v.typ))
if ChanDir(tt.dir)&SendDir == 0 {
panic("reflect: send on recv-only channel")
}
x.mustBeExported()
x = x.assignTo("reflect.Value.Send", tt.elem, nil)
var p unsafe.Pointer
if x.flag&flagIndir != 0 {
p = x.ptr
} else {
p = unsafe.Pointer(&x.ptr)
}
return chansend(v.pointer(), p, nb)
}
// Set assigns x to the value v.
// It panics if CanSet returns false.
// As in Go, x's value must be assignable to v's type.
func (v Value) Set(x Value) {
v.mustBeAssignable()
x.mustBeExported() // do not let unexported x leak
var target unsafe.Pointer
if v.kind() == Interface {
target = v.ptr
}
x = x.assignTo("reflect.Set", v.typ, target)
if x.flag&flagIndir != 0 {
if x.ptr == unsafe.Pointer(&zeroVal[0]) {
typedmemclr(v.typ, v.ptr)
} else {
typedmemmove(v.typ, v.ptr, x.ptr)
}
} else {
*(*unsafe.Pointer)(v.ptr) = x.ptr
}
}
// SetBool sets v's underlying value.
// It panics if v's Kind is not Bool or if CanSet() is false.
func (v Value) SetBool(x bool) {
v.mustBeAssignable()
v.mustBe(Bool)
*(*bool)(v.ptr) = x
}
// SetBytes sets v's underlying value.
// It panics if v's underlying value is not a slice of bytes.
func (v Value) SetBytes(x []byte) {
v.mustBeAssignable()
v.mustBe(Slice)
if v.typ.Elem().Kind() != Uint8 {
panic("reflect.Value.SetBytes of non-byte slice")
}
*(*[]byte)(v.ptr) = x
}
// setRunes sets v's underlying value.
// It panics if v's underlying value is not a slice of runes (int32s).
func (v Value) setRunes(x []rune) {
v.mustBeAssignable()
v.mustBe(Slice)
if v.typ.Elem().Kind() != Int32 {
panic("reflect.Value.setRunes of non-rune slice")
}
*(*[]rune)(v.ptr) = x
}
// SetComplex sets v's underlying value to x.
// It panics if v's Kind is not Complex64 or Complex128, or if CanSet() is false.
func (v Value) SetComplex(x complex128) {
v.mustBeAssignable()
switch k := v.kind(); k {
default:
panic(&ValueError{"reflect.Value.SetComplex", v.kind()})
case Complex64:
*(*complex64)(v.ptr) = complex64(x)
case Complex128:
*(*complex128)(v.ptr) = x
}
}
// SetFloat sets v's underlying value to x.
// It panics if v's Kind is not Float32 or Float64, or if CanSet() is false.
func (v Value) SetFloat(x float64) {
v.mustBeAssignable()
switch k := v.kind(); k {
default:
panic(&ValueError{"reflect.Value.SetFloat", v.kind()})
case Float32:
*(*float32)(v.ptr) = float32(x)
case Float64:
*(*float64)(v.ptr) = x
}
}
// SetInt sets v's underlying value to x.
// It panics if v's Kind is not Int, Int8, Int16, Int32, or Int64, or if CanSet() is false.
func (v Value) SetInt(x int64) {
v.mustBeAssignable()
switch k := v.kind(); k {
default:
panic(&ValueError{"reflect.Value.SetInt", v.kind()})
case Int:
*(*int)(v.ptr) = int(x)
case Int8:
*(*int8)(v.ptr) = int8(x)
case Int16:
*(*int16)(v.ptr) = int16(x)
case Int32:
*(*int32)(v.ptr) = int32(x)
case Int64:
*(*int64)(v.ptr) = x
}
}
// SetLen sets v's length to n.
// It panics if v's Kind is not Slice or if n is negative or
// greater than the capacity of the slice.
func (v Value) SetLen(n int) {
v.mustBeAssignable()
v.mustBe(Slice)
s := (*unsafeheader.Slice)(v.ptr)
if uint(n) > uint(s.Cap) {
panic("reflect: slice length out of range in SetLen")
}
s.Len = n
}
// SetCap sets v's capacity to n.
// It panics if v's Kind is not Slice or if n is smaller than the length or
// greater than the capacity of the slice.
func (v Value) SetCap(n int) {
v.mustBeAssignable()
v.mustBe(Slice)
s := (*unsafeheader.Slice)(v.ptr)
if n < s.Len || n > s.Cap {
panic("reflect: slice capacity out of range in SetCap")
}
s.Cap = n
}
// SetMapIndex sets the element associated with key in the map v to elem.
// It panics if v's Kind is not Map.
// If elem is the zero Value, SetMapIndex deletes the key from the map.
// Otherwise if v holds a nil map, SetMapIndex will panic.
// As in Go, key's elem must be assignable to the map's key type,
// and elem's value must be assignable to the map's elem type.
func (v Value) SetMapIndex(key, elem Value) {
v.mustBe(Map)
v.mustBeExported()
key.mustBeExported()
tt := (*mapType)(unsafe.Pointer(v.typ))
if (tt.key == stringType || key.kind() == String) && tt.key == key.typ && tt.elem.size <= maxValSize {
k := *(*string)(key.ptr)
if elem.typ == nil {
mapdelete_faststr(v.typ, v.pointer(), k)
return
}
elem.mustBeExported()
elem = elem.assignTo("reflect.Value.SetMapIndex", tt.elem, nil)
var e unsafe.Pointer
if elem.flag&flagIndir != 0 {
e = elem.ptr
} else {
e = unsafe.Pointer(&elem.ptr)
}
mapassign_faststr(v.typ, v.pointer(), k, e)
return
}
key = key.assignTo("reflect.Value.SetMapIndex", tt.key, nil)
var k unsafe.Pointer
if key.flag&flagIndir != 0 {
k = key.ptr
} else {
k = unsafe.Pointer(&key.ptr)
}
if elem.typ == nil {
mapdelete(v.typ, v.pointer(), k)
return
}
elem.mustBeExported()
elem = elem.assignTo("reflect.Value.SetMapIndex", tt.elem, nil)
var e unsafe.Pointer
if elem.flag&flagIndir != 0 {
e = elem.ptr
} else {
e = unsafe.Pointer(&elem.ptr)
}
mapassign(v.typ, v.pointer(), k, e)
}
// SetUint sets v's underlying value to x.
// It panics if v's Kind is not Uint, Uintptr, Uint8, Uint16, Uint32, or Uint64, or if CanSet() is false.
func (v Value) SetUint(x uint64) {
v.mustBeAssignable()
switch k := v.kind(); k {
default:
panic(&ValueError{"reflect.Value.SetUint", v.kind()})
case Uint:
*(*uint)(v.ptr) = uint(x)
case Uint8:
*(*uint8)(v.ptr) = uint8(x)
case Uint16:
*(*uint16)(v.ptr) = uint16(x)
case Uint32:
*(*uint32)(v.ptr) = uint32(x)
case Uint64:
*(*uint64)(v.ptr) = x
case Uintptr:
*(*uintptr)(v.ptr) = uintptr(x)
}
}
// SetPointer sets the unsafe.Pointer value v to x.
// It panics if v's Kind is not UnsafePointer.
func (v Value) SetPointer(x unsafe.Pointer) {
v.mustBeAssignable()
v.mustBe(UnsafePointer)
*(*unsafe.Pointer)(v.ptr) = x
}
// SetString sets v's underlying value to x.
// It panics if v's Kind is not String or if CanSet() is false.
func (v Value) SetString(x string) {
v.mustBeAssignable()
v.mustBe(String)
*(*string)(v.ptr) = x
}
// Slice returns v[i:j].
// It panics if v's Kind is not Array, Slice or String, or if v is an unaddressable array,
// or if the indexes are out of bounds.
func (v Value) Slice(i, j int) Value {
var (
cap int
typ *sliceType
base unsafe.Pointer
)
switch kind := v.kind(); kind {
default:
panic(&ValueError{"reflect.Value.Slice", v.kind()})
case Array:
if v.flag&flagAddr == 0 {
panic("reflect.Value.Slice: slice of unaddressable array")
}
tt := (*arrayType)(unsafe.Pointer(v.typ))
cap = int(tt.len)
typ = (*sliceType)(unsafe.Pointer(tt.slice))
base = v.ptr
case Slice:
typ = (*sliceType)(unsafe.Pointer(v.typ))
s := (*unsafeheader.Slice)(v.ptr)
base = s.Data
cap = s.Cap
case String:
s := (*unsafeheader.String)(v.ptr)
if i < 0 || j < i || j > s.Len {
panic("reflect.Value.Slice: string slice index out of bounds")
}
var t unsafeheader.String
if i < s.Len {
t = unsafeheader.String{Data: arrayAt(s.Data, i, 1, "i < s.Len"), Len: j - i}
}
return Value{v.typ, unsafe.Pointer(&t), v.flag}
}
if i < 0 || j < i || j > cap {
panic("reflect.Value.Slice: slice index out of bounds")
}
// Declare slice so that gc can see the base pointer in it.
var x []unsafe.Pointer
// Reinterpret as *unsafeheader.Slice to edit.
s := (*unsafeheader.Slice)(unsafe.Pointer(&x))
s.Len = j - i
s.Cap = cap - i
if cap-i > 0 {
s.Data = arrayAt(base, i, typ.elem.Size(), "i < cap")
} else {
// do not advance pointer, to avoid pointing beyond end of slice
s.Data = base
}
fl := v.flag.ro() | flagIndir | flag(Slice)
return Value{typ.common(), unsafe.Pointer(&x), fl}
}
// Slice3 is the 3-index form of the slice operation: it returns v[i:j:k].
// It panics if v's Kind is not Array or Slice, or if v is an unaddressable array,
// or if the indexes are out of bounds.
func (v Value) Slice3(i, j, k int) Value {
var (
cap int
typ *sliceType
base unsafe.Pointer
)
switch kind := v.kind(); kind {
default:
panic(&ValueError{"reflect.Value.Slice3", v.kind()})
case Array:
if v.flag&flagAddr == 0 {
panic("reflect.Value.Slice3: slice of unaddressable array")
}
tt := (*arrayType)(unsafe.Pointer(v.typ))
cap = int(tt.len)
typ = (*sliceType)(unsafe.Pointer(tt.slice))
base = v.ptr
case Slice:
typ = (*sliceType)(unsafe.Pointer(v.typ))
s := (*unsafeheader.Slice)(v.ptr)
base = s.Data
cap = s.Cap
}
if i < 0 || j < i || k < j || k > cap {
panic("reflect.Value.Slice3: slice index out of bounds")
}
// Declare slice so that the garbage collector
// can see the base pointer in it.
var x []unsafe.Pointer
// Reinterpret as *unsafeheader.Slice to edit.
s := (*unsafeheader.Slice)(unsafe.Pointer(&x))
s.Len = j - i
s.Cap = k - i
if k-i > 0 {
s.Data = arrayAt(base, i, typ.elem.Size(), "i < k <= cap")
} else {
// do not advance pointer, to avoid pointing beyond end of slice
s.Data = base
}
fl := v.flag.ro() | flagIndir | flag(Slice)
return Value{typ.common(), unsafe.Pointer(&x), fl}
}
// String returns the string v's underlying value, as a string.
// String is a special case because of Go's String method convention.
// Unlike the other getters, it does not panic if v's Kind is not String.
// Instead, it returns a string of the form "<T value>" where T is v's type.
// The fmt package treats Values specially. It does not call their String
// method implicitly but instead prints the concrete values they hold.
func (v Value) String() string {
// stringNonString is split out to keep String inlineable for string kinds.
if v.kind() == String {
return *(*string)(v.ptr)
}
return v.stringNonString()
}
func (v Value) stringNonString() string {
if v.kind() == Invalid {
return "<invalid Value>"
}
// If you call String on a reflect.Value of other type, it's better to
// print something than to panic. Useful in debugging.
return "<" + v.Type().String() + " Value>"
}
// TryRecv attempts to receive a value from the channel v but will not block.
// It panics if v's Kind is not Chan.
// If the receive delivers a value, x is the transferred value and ok is true.
// If the receive cannot finish without blocking, x is the zero Value and ok is false.
// If the channel is closed, x is the zero value for the channel's element type and ok is false.
func (v Value) TryRecv() (x Value, ok bool) {
v.mustBe(Chan)
v.mustBeExported()
return v.recv(true)
}
// TrySend attempts to send x on the channel v but will not block.
// It panics if v's Kind is not Chan.
// It reports whether the value was sent.
// As in Go, x's value must be assignable to the channel's element type.
func (v Value) TrySend(x Value) bool {
v.mustBe(Chan)
v.mustBeExported()
return v.send(x, true)
}
// Type returns v's type.
func (v Value) Type() Type {
if v.flag != 0 && v.flag&flagMethod == 0 {
return v.typ
}
return v.typeSlow()
}
func (v Value) typeSlow() Type {
if v.flag == 0 {
panic(&ValueError{"reflect.Value.Type", Invalid})
}
if v.flag&flagMethod == 0 {
return v.typ
}
// Method value.
// v.typ describes the receiver, not the method type.
i := int(v.flag) >> flagMethodShift
if v.typ.Kind() == Interface {
// Method on interface.
tt := (*interfaceType)(unsafe.Pointer(v.typ))
if uint(i) >= uint(len(tt.methods)) {
panic("reflect: internal error: invalid method index")
}
m := &tt.methods[i]
return v.typ.typeOff(m.typ)
}
// Method on concrete type.
ms := v.typ.exportedMethods()
if uint(i) >= uint(len(ms)) {
panic("reflect: internal error: invalid method index")
}
m := ms[i]
return v.typ.typeOff(m.mtyp)
}
// CanUint reports whether Uint can be used without panicking.
func (v Value) CanUint() bool {
switch v.kind() {
case Uint, Uint8, Uint16, Uint32, Uint64, Uintptr:
return true
default:
return false
}
}
// Uint returns v's underlying value, as a uint64.
// It panics if v's Kind is not Uint, Uintptr, Uint8, Uint16, Uint32, or Uint64.
func (v Value) Uint() uint64 {
k := v.kind()
p := v.ptr
switch k {
case Uint:
return uint64(*(*uint)(p))
case Uint8:
return uint64(*(*uint8)(p))
case Uint16:
return uint64(*(*uint16)(p))
case Uint32:
return uint64(*(*uint32)(p))
case Uint64:
return *(*uint64)(p)
case Uintptr:
return uint64(*(*uintptr)(p))
}
panic(&ValueError{"reflect.Value.Uint", v.kind()})
}
//go:nocheckptr
// This prevents inlining Value.UnsafeAddr when -d=checkptr is enabled,
// which ensures cmd/compile can recognize unsafe.Pointer(v.UnsafeAddr())
// and make an exception.
// UnsafeAddr returns a pointer to v's data, as a uintptr.
// It is for advanced clients that also import the "unsafe" package.
// It panics if v is not addressable.
//
// It's preferred to use uintptr(Value.Addr().UnsafePointer()) to get the equivalent result.
func (v Value) UnsafeAddr() uintptr {
if v.typ == nil {
panic(&ValueError{"reflect.Value.UnsafeAddr", Invalid})
}
if v.flag&flagAddr == 0 {
panic("reflect.Value.UnsafeAddr of unaddressable value")
}
return uintptr(v.ptr)
}
// UnsafePointer returns v's value as a unsafe.Pointer.
// It panics if v's Kind is not Chan, Func, Map, Pointer, Slice, or UnsafePointer.
//
// If v's Kind is Func, the returned pointer is an underlying
// code pointer, but not necessarily enough to identify a
// single function uniquely. The only guarantee is that the
// result is zero if and only if v is a nil func Value.
//
// If v's Kind is Slice, the returned pointer is to the first
// element of the slice. If the slice is nil the returned value
// is nil. If the slice is empty but non-nil the return value is non-nil.
func (v Value) UnsafePointer() unsafe.Pointer {
k := v.kind()
switch k {
case Pointer:
if v.typ.ptrdata == 0 {
// Since it is a not-in-heap pointer, all pointers to the heap are
// forbidden! See comment in Value.Elem and issue #48399.
if !verifyNotInHeapPtr(*(*uintptr)(v.ptr)) {
panic("reflect: reflect.Value.UnsafePointer on an invalid notinheap pointer")
}
return *(*unsafe.Pointer)(v.ptr)
}
fallthrough
case Chan, Map, UnsafePointer:
return v.pointer()
case Func:
if v.flag&flagMethod != 0 {
// As the doc comment says, the returned pointer is an
// underlying code pointer but not necessarily enough to
// identify a single function uniquely. All method expressions
// created via reflect have the same underlying code pointer,
// so their Pointers are equal. The function used here must
// match the one used in makeMethodValue.
code := methodValueCallCodePtr()
return *(*unsafe.Pointer)(unsafe.Pointer(&code))
}
p := v.pointer()
// Non-nil func value points at data block.
// First word of data block is actual code.
if p != nil {
p = *(*unsafe.Pointer)(p)
}
return p
case Slice:
return (*unsafeheader.Slice)(v.ptr).Data
}
panic(&ValueError{"reflect.Value.UnsafePointer", v.kind()})
}
// StringHeader is the runtime representation of a string.
// It cannot be used safely or portably and its representation may
// change in a later release.
// Moreover, the Data field is not sufficient to guarantee the data
// it references will not be garbage collected, so programs must keep
// a separate, correctly typed pointer to the underlying data.
type StringHeader struct {
Data uintptr
Len int
}
// SliceHeader is the runtime representation of a slice.
// It cannot be used safely or portably and its representation may
// change in a later release.
// Moreover, the Data field is not sufficient to guarantee the data
// it references will not be garbage collected, so programs must keep
// a separate, correctly typed pointer to the underlying data.
type SliceHeader struct {
Data uintptr
Len int
Cap int
}
func typesMustMatch(what string, t1, t2 Type) {
if t1 != t2 {
panic(what + ": " + t1.String() + " != " + t2.String())
}
}
// arrayAt returns the i-th element of p,
// an array whose elements are eltSize bytes wide.
// The array pointed at by p must have at least i+1 elements:
// it is invalid (but impossible to check here) to pass i >= len,
// because then the result will point outside the array.
// whySafe must explain why i < len. (Passing "i < len" is fine;
// the benefit is to surface this assumption at the call site.)
func arrayAt(p unsafe.Pointer, i int, eltSize uintptr, whySafe string) unsafe.Pointer {
return add(p, uintptr(i)*eltSize, "i < len")
}
// grow grows the slice s so that it can hold extra more values, allocating
// more capacity if needed. It also returns the old and new slice lengths.
func grow(s Value, extra int) (Value, int, int) {
i0 := s.Len()
i1 := i0 + extra
if i1 < i0 {
panic("reflect.Append: slice overflow")
}
m := s.Cap()
if i1 <= m {
return s.Slice(0, i1), i0, i1
}
if m == 0 {
m = extra
} else {
const threshold = 256
for m < i1 {
if i0 < threshold {
m += m
} else {
m += (m + 3*threshold) / 4
}
}
}
t := MakeSlice(s.Type(), i1, m)
Copy(t, s)
return t, i0, i1
}
// Append appends the values x to a slice s and returns the resulting slice.
// As in Go, each x's value must be assignable to the slice's element type.
func Append(s Value, x ...Value) Value {
s.mustBe(Slice)
s, i0, i1 := grow(s, len(x))
for i, j := i0, 0; i < i1; i, j = i+1, j+1 {
s.Index(i).Set(x[j])
}
return s
}
// AppendSlice appends a slice t to a slice s and returns the resulting slice.
// The slices s and t must have the same element type.
func AppendSlice(s, t Value) Value {
s.mustBe(Slice)
t.mustBe(Slice)
typesMustMatch("reflect.AppendSlice", s.Type().Elem(), t.Type().Elem())
s, i0, i1 := grow(s, t.Len())
Copy(s.Slice(i0, i1), t)
return s
}
// Copy copies the contents of src into dst until either
// dst has been filled or src has been exhausted.
// It returns the number of elements copied.
// Dst and src each must have kind Slice or Array, and
// dst and src must have the same element type.
//
// As a special case, src can have kind String if the element type of dst is kind Uint8.
func Copy(dst, src Value) int {
dk := dst.kind()
if dk != Array && dk != Slice {
panic(&ValueError{"reflect.Copy", dk})
}
if dk == Array {
dst.mustBeAssignable()
}
dst.mustBeExported()
sk := src.kind()
var stringCopy bool
if sk != Array && sk != Slice {
stringCopy = sk == String && dst.typ.Elem().Kind() == Uint8
if !stringCopy {
panic(&ValueError{"reflect.Copy", sk})
}
}
src.mustBeExported()
de := dst.typ.Elem()
if !stringCopy {
se := src.typ.Elem()
typesMustMatch("reflect.Copy", de, se)
}
var ds, ss unsafeheader.Slice
if dk == Array {
ds.Data = dst.ptr
ds.Len = dst.Len()
ds.Cap = ds.Len
} else {
ds = *(*unsafeheader.Slice)(dst.ptr)
}
if sk == Array {
ss.Data = src.ptr
ss.Len = src.Len()
ss.Cap = ss.Len
} else if sk == Slice {
ss = *(*unsafeheader.Slice)(src.ptr)
} else {
sh := *(*unsafeheader.String)(src.ptr)
ss.Data = sh.Data
ss.Len = sh.Len
ss.Cap = sh.Len
}
return typedslicecopy(de.common(), ds, ss)
}
// A runtimeSelect is a single case passed to rselect.
// This must match ../runtime/select.go:/runtimeSelect
type runtimeSelect struct {
dir SelectDir // SelectSend, SelectRecv or SelectDefault
typ *rtype // channel type
ch unsafe.Pointer // channel
val unsafe.Pointer // ptr to data (SendDir) or ptr to receive buffer (RecvDir)
}
// rselect runs a select. It returns the index of the chosen case.
// If the case was a receive, val is filled in with the received value.
// The conventional OK bool indicates whether the receive corresponds
// to a sent value.
//
//go:noescape
func rselect([]runtimeSelect) (chosen int, recvOK bool)
// A SelectDir describes the communication direction of a select case.
type SelectDir int
// NOTE: These values must match ../runtime/select.go:/selectDir.
const (
_ SelectDir = iota
SelectSend // case Chan <- Send
SelectRecv // case <-Chan:
SelectDefault // default
)
// A SelectCase describes a single case in a select operation.
// The kind of case depends on Dir, the communication direction.
//
// If Dir is SelectDefault, the case represents a default case.
// Chan and Send must be zero Values.
//
// If Dir is SelectSend, the case represents a send operation.
// Normally Chan's underlying value must be a channel, and Send's underlying value must be
// assignable to the channel's element type. As a special case, if Chan is a zero Value,
// then the case is ignored, and the field Send will also be ignored and may be either zero
// or non-zero.
//
// If Dir is SelectRecv, the case represents a receive operation.
// Normally Chan's underlying value must be a channel and Send must be a zero Value.
// If Chan is a zero Value, then the case is ignored, but Send must still be a zero Value.
// When a receive operation is selected, the received Value is returned by Select.
type SelectCase struct {
Dir SelectDir // direction of case
Chan Value // channel to use (for send or receive)
Send Value // value to send (for send)
}
// Select executes a select operation described by the list of cases.
// Like the Go select statement, it blocks until at least one of the cases
// can proceed, makes a uniform pseudo-random choice,
// and then executes that case. It returns the index of the chosen case
// and, if that case was a receive operation, the value received and a
// boolean indicating whether the value corresponds to a send on the channel
// (as opposed to a zero value received because the channel is closed).
// Select supports a maximum of 65536 cases.
func Select(cases []SelectCase) (chosen int, recv Value, recvOK bool) {
if len(cases) > 65536 {
panic("reflect.Select: too many cases (max 65536)")
}
// NOTE: Do not trust that caller is not modifying cases data underfoot.
// The range is safe because the caller cannot modify our copy of the len
// and each iteration makes its own copy of the value c.
var runcases []runtimeSelect
if len(cases) > 4 {
// Slice is heap allocated due to runtime dependent capacity.
runcases = make([]runtimeSelect, len(cases))
} else {
// Slice can be stack allocated due to constant capacity.
runcases = make([]runtimeSelect, len(cases), 4)
}
haveDefault := false
for i, c := range cases {
rc := &runcases[i]
rc.dir = c.Dir
switch c.Dir {
default:
panic("reflect.Select: invalid Dir")
case SelectDefault: // default
if haveDefault {
panic("reflect.Select: multiple default cases")
}
haveDefault = true
if c.Chan.IsValid() {
panic("reflect.Select: default case has Chan value")
}
if c.Send.IsValid() {
panic("reflect.Select: default case has Send value")
}
case SelectSend:
ch := c.Chan
if !ch.IsValid() {
break
}
ch.mustBe(Chan)
ch.mustBeExported()
tt := (*chanType)(unsafe.Pointer(ch.typ))
if ChanDir(tt.dir)&SendDir == 0 {
panic("reflect.Select: SendDir case using recv-only channel")
}
rc.ch = ch.pointer()
rc.typ = &tt.rtype
v := c.Send
if !v.IsValid() {
panic("reflect.Select: SendDir case missing Send value")
}
v.mustBeExported()
v = v.assignTo("reflect.Select", tt.elem, nil)
if v.flag&flagIndir != 0 {
rc.val = v.ptr
} else {
rc.val = unsafe.Pointer(&v.ptr)
}
case SelectRecv:
if c.Send.IsValid() {
panic("reflect.Select: RecvDir case has Send value")
}
ch := c.Chan
if !ch.IsValid() {
break
}
ch.mustBe(Chan)
ch.mustBeExported()
tt := (*chanType)(unsafe.Pointer(ch.typ))
if ChanDir(tt.dir)&RecvDir == 0 {
panic("reflect.Select: RecvDir case using send-only channel")
}
rc.ch = ch.pointer()
rc.typ = &tt.rtype
rc.val = unsafe_New(tt.elem)
}
}
chosen, recvOK = rselect(runcases)
if runcases[chosen].dir == SelectRecv {
tt := (*chanType)(unsafe.Pointer(runcases[chosen].typ))
t := tt.elem
p := runcases[chosen].val
fl := flag(t.Kind())
if ifaceIndir(t) {
recv = Value{t, p, fl | flagIndir}
} else {
recv = Value{t, *(*unsafe.Pointer)(p), fl}
}
}
return chosen, recv, recvOK
}
/*
* constructors
*/
// implemented in package runtime
func unsafe_New(*rtype) unsafe.Pointer
func unsafe_NewArray(*rtype, int) unsafe.Pointer
// MakeSlice creates a new zero-initialized slice value
// for the specified slice type, length, and capacity.
func MakeSlice(typ Type, len, cap int) Value {
if typ.Kind() != Slice {
panic("reflect.MakeSlice of non-slice type")
}
if len < 0 {
panic("reflect.MakeSlice: negative len")
}
if cap < 0 {
panic("reflect.MakeSlice: negative cap")
}
if len > cap {
panic("reflect.MakeSlice: len > cap")
}
s := unsafeheader.Slice{Data: unsafe_NewArray(typ.Elem().(*rtype), cap), Len: len, Cap: cap}
return Value{typ.(*rtype), unsafe.Pointer(&s), flagIndir | flag(Slice)}
}
// MakeChan creates a new channel with the specified type and buffer size.
func MakeChan(typ Type, buffer int) Value {
if typ.Kind() != Chan {
panic("reflect.MakeChan of non-chan type")
}
if buffer < 0 {
panic("reflect.MakeChan: negative buffer size")
}
if typ.ChanDir() != BothDir {
panic("reflect.MakeChan: unidirectional channel type")
}
t := typ.(*rtype)
ch := makechan(t, buffer)
return Value{t, ch, flag(Chan)}
}
// MakeMap creates a new map with the specified type.
func MakeMap(typ Type) Value {
return MakeMapWithSize(typ, 0)
}
// MakeMapWithSize creates a new map with the specified type
// and initial space for approximately n elements.
func MakeMapWithSize(typ Type, n int) Value {
if typ.Kind() != Map {
panic("reflect.MakeMapWithSize of non-map type")
}
t := typ.(*rtype)
m := makemap(t, n)
return Value{t, m, flag(Map)}
}
// Indirect returns the value that v points to.
// If v is a nil pointer, Indirect returns a zero Value.
// If v is not a pointer, Indirect returns v.
func Indirect(v Value) Value {
if v.Kind() != Pointer {
return v
}
return v.Elem()
}
// ValueOf returns a new Value initialized to the concrete value
// stored in the interface i. ValueOf(nil) returns the zero Value.
func ValueOf(i any) Value {
if i == nil {
return Value{}
}
// TODO: Maybe allow contents of a Value to live on the stack.
// For now we make the contents always escape to the heap. It
// makes life easier in a few places (see chanrecv/mapassign
// comment below).
escapes(i)
return unpackEface(i)
}
// Zero returns a Value representing the zero value for the specified type.
// The result is different from the zero value of the Value struct,
// which represents no value at all.
// For example, Zero(TypeOf(42)) returns a Value with Kind Int and value 0.
// The returned value is neither addressable nor settable.
func Zero(typ Type) Value {
if typ == nil {
panic("reflect: Zero(nil)")
}
t := typ.(*rtype)
fl := flag(t.Kind())
if ifaceIndir(t) {
var p unsafe.Pointer
if t.size <= maxZero {
p = unsafe.Pointer(&zeroVal[0])
} else {
p = unsafe_New(t)
}
return Value{t, p, fl | flagIndir}
}
return Value{t, nil, fl}
}
// must match declarations in runtime/map.go.
const maxZero = 1024
//go:linkname zeroVal runtime.zeroVal
var zeroVal [maxZero]byte
// New returns a Value representing a pointer to a new zero value
// for the specified type. That is, the returned Value's Type is PointerTo(typ).
func New(typ Type) Value {
if typ == nil {
panic("reflect: New(nil)")
}
t := typ.(*rtype)
pt := t.ptrTo()
if ifaceIndir(pt) {
// This is a pointer to a go:notinheap type.
panic("reflect: New of type that may not be allocated in heap (possibly undefined cgo C type)")
}
ptr := unsafe_New(t)
fl := flag(Pointer)
return Value{pt, ptr, fl}
}
// NewAt returns a Value representing a pointer to a value of the
// specified type, using p as that pointer.
func NewAt(typ Type, p unsafe.Pointer) Value {
fl := flag(Pointer)
t := typ.(*rtype)
return Value{t.ptrTo(), p, fl}
}
// assignTo returns a value v that can be assigned directly to dst.
// It panics if v is not assignable to dst.
// For a conversion to an interface type, target, if not nil,
// is a suggested scratch space to use.
// target must be initialized memory (or nil).
func (v Value) assignTo(context string, dst *rtype, target unsafe.Pointer) Value {
if v.flag&flagMethod != 0 {
v = makeMethodValue(context, v)
}
switch {
case directlyAssignable(dst, v.typ):
// Overwrite type so that they match.
// Same memory layout, so no harm done.
fl := v.flag&(flagAddr|flagIndir) | v.flag.ro()
fl |= flag(dst.Kind())
return Value{dst, v.ptr, fl}
case implements(dst, v.typ):
if v.Kind() == Interface && v.IsNil() {
// A nil ReadWriter passed to nil Reader is OK,
// but using ifaceE2I below will panic.
// Avoid the panic by returning a nil dst (e.g., Reader) explicitly.
return Value{dst, nil, flag(Interface)}
}
x := valueInterface(v, false)
if target == nil {
target = unsafe_New(dst)
}
if dst.NumMethod() == 0 {
*(*any)(target) = x
} else {
ifaceE2I(dst, x, target)
}
return Value{dst, target, flagIndir | flag(Interface)}
}
// Failed.
panic(context + ": value of type " + v.typ.String() + " is not assignable to type " + dst.String())
}
// Convert returns the value v converted to type t.
// If the usual Go conversion rules do not allow conversion
// of the value v to type t, or if converting v to type t panics, Convert panics.
func (v Value) Convert(t Type) Value {
if v.flag&flagMethod != 0 {
v = makeMethodValue("Convert", v)
}
op := convertOp(t.common(), v.typ)
if op == nil {
panic("reflect.Value.Convert: value of type " + v.typ.String() + " cannot be converted to type " + t.String())
}
return op(v, t)
}
// CanConvert reports whether the value v can be converted to type t.
// If v.CanConvert(t) returns true then v.Convert(t) will not panic.
func (v Value) CanConvert(t Type) bool {
vt := v.Type()
if !vt.ConvertibleTo(t) {
return false
}
// Currently the only conversion that is OK in terms of type
// but that can panic depending on the value is converting
// from slice to pointer-to-array.
if vt.Kind() == Slice && t.Kind() == Pointer && t.Elem().Kind() == Array {
n := t.Elem().Len()
if n > v.Len() {
return false
}
}
return true
}
// convertOp returns the function to convert a value of type src
// to a value of type dst. If the conversion is illegal, convertOp returns nil.
func convertOp(dst, src *rtype) func(Value, Type) Value {
switch src.Kind() {
case Int, Int8, Int16, Int32, Int64:
switch dst.Kind() {
case Int, Int8, Int16, Int32, Int64, Uint, Uint8, Uint16, Uint32, Uint64, Uintptr:
return cvtInt
case Float32, Float64:
return cvtIntFloat
case String:
return cvtIntString
}
case Uint, Uint8, Uint16, Uint32, Uint64, Uintptr:
switch dst.Kind() {
case Int, Int8, Int16, Int32, Int64, Uint, Uint8, Uint16, Uint32, Uint64, Uintptr:
return cvtUint
case Float32, Float64:
return cvtUintFloat
case String:
return cvtUintString
}
case Float32, Float64:
switch dst.Kind() {
case Int, Int8, Int16, Int32, Int64:
return cvtFloatInt
case Uint, Uint8, Uint16, Uint32, Uint64, Uintptr:
return cvtFloatUint
case Float32, Float64:
return cvtFloat
}
case Complex64, Complex128:
switch dst.Kind() {
case Complex64, Complex128:
return cvtComplex
}
case String:
if dst.Kind() == Slice && dst.Elem().PkgPath() == "" {
switch dst.Elem().Kind() {
case Uint8:
return cvtStringBytes
case Int32:
return cvtStringRunes
}
}
case Slice:
if dst.Kind() == String && src.Elem().PkgPath() == "" {
switch src.Elem().Kind() {
case Uint8:
return cvtBytesString
case Int32:
return cvtRunesString
}
}
// "x is a slice, T is a pointer-to-array type,
// and the slice and array types have identical element types."
if dst.Kind() == Pointer && dst.Elem().Kind() == Array && src.Elem() == dst.Elem().Elem() {
return cvtSliceArrayPtr
}
case Chan:
if dst.Kind() == Chan && specialChannelAssignability(dst, src) {
return cvtDirect
}
}
// dst and src have same underlying type.
if haveIdenticalUnderlyingType(dst, src, false) {
return cvtDirect
}
// dst and src are non-defined pointer types with same underlying base type.
if dst.Kind() == Pointer && dst.Name() == "" &&
src.Kind() == Pointer && src.Name() == "" &&
haveIdenticalUnderlyingType(dst.Elem().common(), src.Elem().common(), false) {
return cvtDirect
}
if implements(dst, src) {
if src.Kind() == Interface {
return cvtI2I
}
return cvtT2I
}
return nil
}
// makeInt returns a Value of type t equal to bits (possibly truncated),
// where t is a signed or unsigned int type.
func makeInt(f flag, bits uint64, t Type) Value {
typ := t.common()
ptr := unsafe_New(typ)
switch typ.size {
case 1:
*(*uint8)(ptr) = uint8(bits)
case 2:
*(*uint16)(ptr) = uint16(bits)
case 4:
*(*uint32)(ptr) = uint32(bits)
case 8:
*(*uint64)(ptr) = bits
}
return Value{typ, ptr, f | flagIndir | flag(typ.Kind())}
}
// makeFloat returns a Value of type t equal to v (possibly truncated to float32),
// where t is a float32 or float64 type.
func makeFloat(f flag, v float64, t Type) Value {
typ := t.common()
ptr := unsafe_New(typ)
switch typ.size {
case 4:
*(*float32)(ptr) = float32(v)
case 8:
*(*float64)(ptr) = v
}
return Value{typ, ptr, f | flagIndir | flag(typ.Kind())}
}
// makeFloat returns a Value of type t equal to v, where t is a float32 type.
func makeFloat32(f flag, v float32, t Type) Value {
typ := t.common()
ptr := unsafe_New(typ)
*(*float32)(ptr) = v
return Value{typ, ptr, f | flagIndir | flag(typ.Kind())}
}
// makeComplex returns a Value of type t equal to v (possibly truncated to complex64),
// where t is a complex64 or complex128 type.
func makeComplex(f flag, v complex128, t Type) Value {
typ := t.common()
ptr := unsafe_New(typ)
switch typ.size {
case 8:
*(*complex64)(ptr) = complex64(v)
case 16:
*(*complex128)(ptr) = v
}
return Value{typ, ptr, f | flagIndir | flag(typ.Kind())}
}
func makeString(f flag, v string, t Type) Value {
ret := New(t).Elem()
ret.SetString(v)
ret.flag = ret.flag&^flagAddr | f
return ret
}
func makeBytes(f flag, v []byte, t Type) Value {
ret := New(t).Elem()
ret.SetBytes(v)
ret.flag = ret.flag&^flagAddr | f
return ret
}
func makeRunes(f flag, v []rune, t Type) Value {
ret := New(t).Elem()
ret.setRunes(v)
ret.flag = ret.flag&^flagAddr | f
return ret
}
// These conversion functions are returned by convertOp
// for classes of conversions. For example, the first function, cvtInt,
// takes any value v of signed int type and returns the value converted
// to type t, where t is any signed or unsigned int type.
// convertOp: intXX -> [u]intXX
func cvtInt(v Value, t Type) Value {
return makeInt(v.flag.ro(), uint64(v.Int()), t)
}
// convertOp: uintXX -> [u]intXX
func cvtUint(v Value, t Type) Value {
return makeInt(v.flag.ro(), v.Uint(), t)
}
// convertOp: floatXX -> intXX
func cvtFloatInt(v Value, t Type) Value {
return makeInt(v.flag.ro(), uint64(int64(v.Float())), t)
}
// convertOp: floatXX -> uintXX
func cvtFloatUint(v Value, t Type) Value {
return makeInt(v.flag.ro(), uint64(v.Float()), t)
}
// convertOp: intXX -> floatXX
func cvtIntFloat(v Value, t Type) Value {
return makeFloat(v.flag.ro(), float64(v.Int()), t)
}
// convertOp: uintXX -> floatXX
func cvtUintFloat(v Value, t Type) Value {
return makeFloat(v.flag.ro(), float64(v.Uint()), t)
}
// convertOp: floatXX -> floatXX
func cvtFloat(v Value, t Type) Value {
if v.Type().Kind() == Float32 && t.Kind() == Float32 {
// Don't do any conversion if both types have underlying type float32.
// This avoids converting to float64 and back, which will
// convert a signaling NaN to a quiet NaN. See issue 36400.
return makeFloat32(v.flag.ro(), *(*float32)(v.ptr), t)
}
return makeFloat(v.flag.ro(), v.Float(), t)
}
// convertOp: complexXX -> complexXX
func cvtComplex(v Value, t Type) Value {
return makeComplex(v.flag.ro(), v.Complex(), t)
}
// convertOp: intXX -> string
func cvtIntString(v Value, t Type) Value {
s := "\uFFFD"
if x := v.Int(); int64(rune(x)) == x {
s = string(rune(x))
}
return makeString(v.flag.ro(), s, t)
}
// convertOp: uintXX -> string
func cvtUintString(v Value, t Type) Value {
s := "\uFFFD"
if x := v.Uint(); uint64(rune(x)) == x {
s = string(rune(x))
}
return makeString(v.flag.ro(), s, t)
}
// convertOp: []byte -> string
func cvtBytesString(v Value, t Type) Value {
return makeString(v.flag.ro(), string(v.Bytes()), t)
}
// convertOp: string -> []byte
func cvtStringBytes(v Value, t Type) Value {
return makeBytes(v.flag.ro(), []byte(v.String()), t)
}
// convertOp: []rune -> string
func cvtRunesString(v Value, t Type) Value {
return makeString(v.flag.ro(), string(v.runes()), t)
}
// convertOp: string -> []rune
func cvtStringRunes(v Value, t Type) Value {
return makeRunes(v.flag.ro(), []rune(v.String()), t)
}
// convertOp: []T -> *[N]T
func cvtSliceArrayPtr(v Value, t Type) Value {
n := t.Elem().Len()
if n > v.Len() {
panic("reflect: cannot convert slice with length " + itoa.Itoa(v.Len()) + " to pointer to array with length " + itoa.Itoa(n))
}
h := (*unsafeheader.Slice)(v.ptr)
return Value{t.common(), h.Data, v.flag&^(flagIndir|flagAddr|flagKindMask) | flag(Pointer)}
}
// convertOp: direct copy
func cvtDirect(v Value, typ Type) Value {
f := v.flag
t := typ.common()
ptr := v.ptr
if f&flagAddr != 0 {
// indirect, mutable word - make a copy
c := unsafe_New(t)
typedmemmove(t, c, ptr)
ptr = c
f &^= flagAddr
}
return Value{t, ptr, v.flag.ro() | f} // v.flag.ro()|f == f?
}
// convertOp: concrete -> interface
func cvtT2I(v Value, typ Type) Value {
target := unsafe_New(typ.common())
x := valueInterface(v, false)
if typ.NumMethod() == 0 {
*(*any)(target) = x
} else {
ifaceE2I(typ.(*rtype), x, target)
}
return Value{typ.common(), target, v.flag.ro() | flagIndir | flag(Interface)}
}
// convertOp: interface -> interface
func cvtI2I(v Value, typ Type) Value {
if v.IsNil() {
ret := Zero(typ)
ret.flag |= v.flag.ro()
return ret
}
return cvtT2I(v.Elem(), typ)
}
// implemented in ../runtime
func chancap(ch unsafe.Pointer) int
func chanclose(ch unsafe.Pointer)
func chanlen(ch unsafe.Pointer) int
// Note: some of the noescape annotations below are technically a lie,
// but safe in the context of this package. Functions like chansend
// and mapassign don't escape the referent, but may escape anything
// the referent points to (they do shallow copies of the referent).
// It is safe in this package because the referent may only point
// to something a Value may point to, and that is always in the heap
// (due to the escapes() call in ValueOf).
//go:noescape
func chanrecv(ch unsafe.Pointer, nb bool, val unsafe.Pointer) (selected, received bool)
//go:noescape
func chansend(ch unsafe.Pointer, val unsafe.Pointer, nb bool) bool
func makechan(typ *rtype, size int) (ch unsafe.Pointer)
func makemap(t *rtype, cap int) (m unsafe.Pointer)
//go:noescape
func mapaccess(t *rtype, m unsafe.Pointer, key unsafe.Pointer) (val unsafe.Pointer)
//go:noescape
func mapaccess_faststr(t *rtype, m unsafe.Pointer, key string) (val unsafe.Pointer)
//go:noescape
func mapassign(t *rtype, m unsafe.Pointer, key, val unsafe.Pointer)
//go:noescape
func mapassign_faststr(t *rtype, m unsafe.Pointer, key string, val unsafe.Pointer)
//go:noescape
func mapdelete(t *rtype, m unsafe.Pointer, key unsafe.Pointer)
//go:noescape
func mapdelete_faststr(t *rtype, m unsafe.Pointer, key string)
//go:noescape
func mapiterinit(t *rtype, m unsafe.Pointer, it *hiter)
//go:noescape
func mapiterkey(it *hiter) (key unsafe.Pointer)
//go:noescape
func mapiterelem(it *hiter) (elem unsafe.Pointer)
//go:noescape
func mapiternext(it *hiter)
//go:noescape
func maplen(m unsafe.Pointer) int
// call calls fn with "stackArgsSize" bytes of stack arguments laid out
// at stackArgs and register arguments laid out in regArgs. frameSize is
// the total amount of stack space that will be reserved by call, so this
// should include enough space to spill register arguments to the stack in
// case of preemption.
//
// After fn returns, call copies stackArgsSize-stackRetOffset result bytes
// back into stackArgs+stackRetOffset before returning, for any return
// values passed on the stack. Register-based return values will be found
// in the same regArgs structure.
//
// regArgs must also be prepared with an appropriate ReturnIsPtr bitmap
// indicating which registers will contain pointer-valued return values. The
// purpose of this bitmap is to keep pointers visible to the GC between
// returning from reflectcall and actually using them.
//
// If copying result bytes back from the stack, the caller must pass the
// argument frame type as stackArgsType, so that call can execute appropriate
// write barriers during the copy.
//
// Arguments passed through to call do not escape. The type is used only in a
// very limited callee of call, the stackArgs are copied, and regArgs is only
// used in the call frame.
//
//go:noescape
//go:linkname call runtime.reflectcall
func call(stackArgsType *rtype, f, stackArgs unsafe.Pointer, stackArgsSize, stackRetOffset, frameSize uint32, regArgs *abi.RegArgs)
func ifaceE2I(t *rtype, src any, dst unsafe.Pointer)
// memmove copies size bytes to dst from src. No write barriers are used.
//
//go:noescape
func memmove(dst, src unsafe.Pointer, size uintptr)
// typedmemmove copies a value of type t to dst from src.
//
//go:noescape
func typedmemmove(t *rtype, dst, src unsafe.Pointer)
// typedmemmovepartial is like typedmemmove but assumes that
// dst and src point off bytes into the value and only copies size bytes.
//
//go:noescape
func typedmemmovepartial(t *rtype, dst, src unsafe.Pointer, off, size uintptr)
// typedmemclr zeros the value at ptr of type t.
//
//go:noescape
func typedmemclr(t *rtype, ptr unsafe.Pointer)
// typedmemclrpartial is like typedmemclr but assumes that
// dst points off bytes into the value and only clears size bytes.
//
//go:noescape
func typedmemclrpartial(t *rtype, ptr unsafe.Pointer, off, size uintptr)
// typedslicecopy copies a slice of elemType values from src to dst,
// returning the number of elements copied.
//
//go:noescape
func typedslicecopy(elemType *rtype, dst, src unsafeheader.Slice) int
//go:noescape
func typehash(t *rtype, p unsafe.Pointer, h uintptr) uintptr
func verifyNotInHeapPtr(p uintptr) bool
// Dummy annotation marking that the value x escapes,
// for use in cases where the reflect code is so clever that
// the compiler cannot follow.
func escapes(x any) {
if dummy.b {
dummy.x = x
}
}
var dummy struct {
b bool
x any
}
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