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