golang dump 代码
文件路径：/src/cmd/compile/internal/ir/dump.go
/ Copyright 2018 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.
/ This file implements textual dumping of arbitrary data structures
/ for debugging purposes. The code is customized for Node graphs
/ and may be used for an alternative view of the node structure.
package ir
import (
"fmt"
"io"
"os"
"reflect"
"regexp"
"cmd/compile/internal/base"
"cmd/compile/internal/types"
"cmd/internal/src"
)
/ DumpAny is like FDumpAny but prints to stderr.
func DumpAny(root interface{}, filter string, depth int) {
FDumpAny(os.Stderr, root, filter, depth)
}
/ FDumpAny prints the structure of a rooted data structure
/ to w by depth-first traversal of the data structure.
/
/ The filter parameter is a regular expression. If it is
/ non-empty, only struct fields whose names match filter
/ are printed.
/
/ The depth parameter controls how deep traversal recurses
/ before it returns (higher value means greater depth).
/ If an empty field filter is given, a good depth default value
/ is 4. A negative depth means no depth limit, which may be fine
/ for small data structures or if there is a non-empty filter.
/
/ In the output, Node structs are identified by their Op name
/ rather than their type; struct fields with zero values or
/ non-matching field names are omitted, and "…" means recursion
/ depth has been reached or struct fields have been omitted.
func FDumpAny(w io.Writer, root interface{}, filter string, depth int) {
if root == nil {
fmt.Fprintln(w, "nil")
return
}
if filter == "" {
filter = ".*" / default
}
p := dumper{
output: w,
fieldrx: regexp.MustCompile(filter),
ptrmap: make(map[uintptr]int),
last: '\n', / force printing of line number on first line
}
p.dump(reflect.ValueOf(root), depth)
p.printf("\n")
}
type dumper struct {
output io.Writer
fieldrx *regexp.Regexp / field name filter
ptrmap map[uintptr]int / ptr -> dump line number
lastadr string / last address string printed (for shortening)
/ output
indent int / current indentation level
last byte / last byte processed by Write
line int / current line number
}
var indentBytes = []byte(". ")
func (p *dumper) Write(data []byte) (n int, err error) {
var m int
for i, b := range data {
/ invariant: data[0:n] has been written
if b == '\n' {
m, err = p.output.Write(data[n : i+1])
n += m
if err != nil {
return
}
} else if p.last == '\n' {
p.line++
_, err = fmt.Fprintf(p.output, "%6d ", p.line)
if err != nil {
return
}
for j := p.indent; j > 0; j-- {
_, err = p.output.Write(indentBytes)
if err != nil {
return
}
}
}
p.last = b
}
if len(data) > n {
m, err = p.output.Write(data[n:])
n += m
}
return
}
/ printf is a convenience wrapper.
func (p *dumper) printf(format string, args ...interface{}) {
if _, err := fmt.Fprintf(p, format, args...); err != nil {
panic(err)
}
}
/ addr returns the (hexadecimal) address string of the object
/ represented by x (or "?" if x is not addressable), with the
/ common prefix between this and the prior address replaced by
/ "0x…" to make it easier to visually match addresses.
func (p *dumper) addr(x reflect.Value) string {
if !x.CanAddr() {
return "?"
}
adr := fmt.Sprintf("%p", x.Addr().Interface())
s := adr
if i := commonPrefixLen(p.lastadr, adr); i > 0 {
s = "0x…" + adr[i:]
}
p.lastadr = adr
return s
}
/ dump prints the contents of x.
func (p *dumper) dump(x reflect.Value, depth int) {
if depth == 0 {
p.printf("…")
return
}
if pos, ok := x.Interface().(src.XPos); ok {
p.printf("%s", base.FmtPos(pos))
return
}
switch x.Kind() {
case reflect.String:
p.printf("%q", x.Interface()) / print strings in quotes
case reflect.Interface:
if x.IsNil() {
p.printf("nil")
return
}
p.dump(x.Elem(), depth-1)
case reflect.Ptr:
if x.IsNil() {
p.printf("nil")
return
}
p.printf("*")
ptr := x.Pointer()
if line, exists := p.ptrmap[ptr]; exists {
p.printf("(@%d)", line)
return
}
p.ptrmap[ptr] = p.line
p.dump(x.Elem(), depth) / don't count pointer indirection towards depth
case reflect.Slice:
if x.IsNil() {
p.printf("nil")
return
}
p.printf("%s (%d entries) {", x.Type(), x.Len())
if x.Len() > 0 {
p.indent++
p.printf("\n")
for i, n := 0, x.Len(); i < n; i++ {
p.printf("%d: ", i)
p.dump(x.Index(i), depth-1)
p.printf("\n")
}
p.indent--
}
p.printf("}")
case reflect.Struct:
typ := x.Type()
isNode := false
if n, ok := x.Interface().(Node); ok {
isNode = true
p.printf("%s %s {", n.Op().String(), p.addr(x))
} else {
p.printf("%s {", typ)
}
p.indent++
first := true
omitted := false
for i, n := 0, typ.NumField(); i < n; i++ {
/ Exclude non-exported fields because their
/ values cannot be accessed via reflection.
if name := typ.Field(i).Name; types.IsExported(name) {
if !p.fieldrx.MatchString(name) {
omitted = true
continue / field name not selected by filter
}
/ special cases
if isNode && name == "Op" {
omitted = true
continue / Op field already printed for Nodes
}
x := x.Field(i)
if isZeroVal(x) {
omitted = true
continue / exclude zero-valued fields
}
if n, ok := x.Interface().(Nodes); ok && len(n) == 0 {
omitted = true
continue / exclude empty Nodes slices
}
if first {
p.printf("\n")
first = false
}
p.printf("%s: ", name)
p.dump(x, depth-1)
p.printf("\n")
}
}
if omitted {
p.printf("…\n")
}
p.indent--
p.printf("}")
default:
p.printf("%v", x.Interface())
}
}
func isZeroVal(x reflect.Value) bool {
switch x.Kind() {
case reflect.Bool:
return !x.Bool()
case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
return x.Int() == 0
case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
return x.Uint() == 0
case reflect.String:
return x.String() == ""
case reflect.Interface, reflect.Ptr, reflect.Slice:
return x.IsNil()
}
return false
}
func commonPrefixLen(a, b string) (i int) {
for i < len(a) && i < len(b) && a[i] == b[i] {
i++
}
return
}