mirror of
https://github.com/mozilla/gecko-dev.git
synced 2024-11-01 14:45:29 +00:00
97 lines
2.2 KiB
C++
97 lines
2.2 KiB
C++
/* 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/. */
|
|
|
|
#include "mozilla/Assertions.h"
|
|
#include "nsAlgorithm.h"
|
|
#include "nsDebug.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(nsMallocSizeOfFun aMallocSizeOf) const;
|
|
|
|
// our current position in memory
|
|
size_t mPos;
|
|
|
|
// a list of memory block. Usually there is only one
|
|
// but if we overrun our stack size we can get more memory.
|
|
StackBlock* mBlocks;
|
|
|
|
// the current block of memory we are passing our chucks of
|
|
StackBlock* mCurBlock;
|
|
|
|
// our stack of mark where push has been called
|
|
StackMark* mMarks;
|
|
|
|
// the current top of the mark list
|
|
PRUint32 mStackTop;
|
|
|
|
// the size of the mark array
|
|
PRUint32 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.
|
|
*
|
|
* The allocations cannot be for more than 4044 bytes.
|
|
*/
|
|
class NS_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) {
|
|
MOZ_ASSERT(aSize <= 4044);
|
|
return gStackArena->Allocate(aSize);
|
|
}
|
|
|
|
private:
|
|
static StackArena* gStackArena;
|
|
bool mOwnsStackArena;
|
|
};
|
|
|
|
|
|
} // namespace mozilla
|