golang mem_js 代码
文件路径：/src/runtime/mem_js.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.
/go:build js && wasm
package runtime
import (
"unsafe"
)
/ Don't split the stack as this function may be invoked without a valid G,
/ which prevents us from allocating more stack.
/
/go:nosplit
func sysAllocOS(n uintptr) unsafe.Pointer {
p := sysReserveOS(nil, n)
sysMapOS(p, n)
return p
}
func sysUnusedOS(v unsafe.Pointer, n uintptr) {
}
func sysUsedOS(v unsafe.Pointer, n uintptr) {
}
func sysHugePageOS(v unsafe.Pointer, n uintptr) {
}
/ Don't split the stack as this function may be invoked without a valid G,
/ which prevents us from allocating more stack.
/
/go:nosplit
func sysFreeOS(v unsafe.Pointer, n uintptr) {
}
func sysFaultOS(v unsafe.Pointer, n uintptr) {
}
var reserveEnd uintptr
func sysReserveOS(v unsafe.Pointer, n uintptr) unsafe.Pointer {
/ TODO(neelance): maybe unify with mem_plan9.go, depending on how https://github.com/WebAssembly/design/blob/master/FutureFeatures.md#finer-grained-control-over-memory turns out
if v != nil {
/ The address space of WebAssembly's linear memory is contiguous,
/ so requesting specific addresses is not supported. We could use
/ a different address, but then mheap.sysAlloc discards the result
/ right away and we don't reuse chunks passed to sysFree.
return nil
}
/ Round up the initial reserveEnd to 64 KiB so that
/ reservations are always aligned to the page size.
initReserveEnd := alignUp(lastmoduledatap.end, physPageSize)
if reserveEnd < initReserveEnd {
reserveEnd = initReserveEnd
}
v = unsafe.Pointer(reserveEnd)
reserveEnd += alignUp(n, physPageSize)
current := currentMemory()
/ reserveEnd is always at a page boundary.
needed := int32(reserveEnd / physPageSize)
if current < needed {
if growMemory(needed-current) == -1 {
return nil
}
resetMemoryDataView()
}
return v
}
func currentMemory() int32
func growMemory(pages int32) int32
/ resetMemoryDataView signals the JS front-end that WebAssembly's memory.grow instruction has been used.
/ This allows the front-end to replace the old DataView object with a new one.
func resetMemoryDataView()
func sysMapOS(v unsafe.Pointer, n uintptr) {
}