Current File : //usr/local/go/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
// +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 sysAlloc(n uintptr, sysStat *sysMemStat) unsafe.Pointer {
p := sysReserve(nil, n)
sysMap(p, n, sysStat)
return p
}
func sysUnused(v unsafe.Pointer, n uintptr) {
}
func sysUsed(v unsafe.Pointer, n uintptr) {
}
func sysHugePage(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 sysFree(v unsafe.Pointer, n uintptr, sysStat *sysMemStat) {
sysStat.add(-int64(n))
}
func sysFault(v unsafe.Pointer, n uintptr) {
}
var reserveEnd uintptr
func sysReserve(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 sysMap(v unsafe.Pointer, n uintptr, sysStat *sysMemStat) {
sysStat.add(int64(n))
}
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