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/* 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 http://mozilla.org/MPL/2.0/. */
#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 {
private:
friend class AutoStackArena;
StackArena();
~StackArena();
nsresult Init() { return mBlocks ? NS_OK : NS_ERROR_OUT_OF_MEMORY; }
// 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_STACK_CLASS AutoStackArena {
public:
AutoStackArena()
: mOwnsStackArena(false)
{
if (!gStackArena) {
gStackArena = new StackArena();
mOwnsStackArena = true;
gStackArena->Init();
}
gStackArena->Push();
}
~AutoStackArena() {
gStackArena->Pop();
if (mOwnsStackArena) {
delete gStackArena;
gStackArena = nullptr;
}
}
static void* Allocate(size_t aSize) {
return gStackArena->Allocate(aSize);
}
private:
static StackArena* gStackArena;
bool mOwnsStackArena;
};
} // namespace mozilla
#endif
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