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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this file,
* You can obtain one at */
#ifndef StackArena_h
#define StackArena_h
#include "nsError.h"
#include "mozilla/Assertions.h"
#include "mozilla/MemoryReporting.h"
namespace mozilla {
struct StackBlock;
struct StackMark;
class AutoStackArena;
// Private helper class for AutoStackArena.
class StackArena {
friend class AutoStackArena;
// Memory management functions.
void* Allocate(size_t aSize);
void Push();
void Pop();
size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
// Our current position in memory.
size_t mPos;
// A list of memory blocks. Usually there is only one
// but if we overrun our stack size we can get more memory.
StackBlock* mBlocks;
// The current block.
StackBlock* mCurBlock;
// Our stack of mark where push has been called.
StackMark* mMarks;
// The current top of the mark list.
uint32_t mStackTop;
// The size of the mark array.
uint32_t mMarkLength;
// Class for stack scoped arena memory allocations.
// Callers who wish to allocate memory whose lifetime corresponds to the
// lifetime of a stack-allocated object can use this class. First,
// declare an AutoStackArena object on the stack. Then all subsequent
// calls to Allocate will allocate memory from an arena pool that will
// be freed when that variable goes out of scope. Nesting is allowed.
// Individual allocations cannot exceed StackBlock::MAX_USABLE_SIZE
// bytes.
class MOZ_RAII AutoStackArena {
AutoStackArena() : mOwnsStackArena(false) {
if (!gStackArena) {
gStackArena = new StackArena();
mOwnsStackArena = true;
~AutoStackArena() {
if (mOwnsStackArena) {
delete gStackArena;
gStackArena = nullptr;
static void* Allocate(size_t aSize) { return gStackArena->Allocate(aSize); }
static StackArena* gStackArena;
bool mOwnsStackArena;
} // namespace mozilla