michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
michael@0:  * You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: #ifndef StackArena_h
michael@0: #define StackArena_h
michael@0: 
michael@0: #include "nsError.h"
michael@0: #include "mozilla/Assertions.h"
michael@0: #include "mozilla/MemoryReporting.h"
michael@0: #include "mozilla/NullPtr.h"
michael@0: 
michael@0: namespace mozilla {
michael@0: 
michael@0: struct StackBlock;
michael@0: struct StackMark;
michael@0: class AutoStackArena;
michael@0: 
michael@0: // Private helper class for AutoStackArena.
michael@0: class StackArena {
michael@0: private:
michael@0:   friend class AutoStackArena;
michael@0:   StackArena();
michael@0:   ~StackArena();
michael@0: 
michael@0:   nsresult Init() { return mBlocks ? NS_OK : NS_ERROR_OUT_OF_MEMORY; }
michael@0: 
michael@0:   // Memory management functions.
michael@0:   void* Allocate(size_t aSize);
michael@0:   void Push();
michael@0:   void Pop();
michael@0: 
michael@0:   size_t SizeOfExcludingThis(mozilla::MallocSizeOf aMallocSizeOf) const;
michael@0: 
michael@0:   // Our current position in memory.
michael@0:   size_t mPos;
michael@0: 
michael@0:   // A list of memory blocks. Usually there is only one
michael@0:   // but if we overrun our stack size we can get more memory.
michael@0:   StackBlock* mBlocks;
michael@0: 
michael@0:   // The current block.
michael@0:   StackBlock* mCurBlock;
michael@0: 
michael@0:   // Our stack of mark where push has been called.
michael@0:   StackMark* mMarks;
michael@0: 
michael@0:   // The current top of the mark list.
michael@0:   uint32_t mStackTop;
michael@0: 
michael@0:   // The size of the mark array.
michael@0:   uint32_t mMarkLength;
michael@0: };
michael@0: 
michael@0: // Class for stack scoped arena memory allocations.
michael@0: //
michael@0: // Callers who wish to allocate memory whose lifetime corresponds to the
michael@0: // lifetime of a stack-allocated object can use this class.  First,
michael@0: // declare an AutoStackArena object on the stack.  Then all subsequent
michael@0: // calls to Allocate will allocate memory from an arena pool that will
michael@0: // be freed when that variable goes out of scope.  Nesting is allowed.
michael@0: //
michael@0: // Individual allocations cannot exceed StackBlock::MAX_USABLE_SIZE
michael@0: // bytes.
michael@0: //
michael@0: class MOZ_STACK_CLASS AutoStackArena {
michael@0: public:
michael@0:   AutoStackArena()
michael@0:     : mOwnsStackArena(false)
michael@0:   {
michael@0:     if (!gStackArena) {
michael@0:       gStackArena = new StackArena();
michael@0:       mOwnsStackArena = true;
michael@0:       gStackArena->Init();
michael@0:     }
michael@0:     gStackArena->Push();
michael@0:   }
michael@0: 
michael@0:   ~AutoStackArena() {
michael@0:     gStackArena->Pop();
michael@0:     if (mOwnsStackArena) {
michael@0:       delete gStackArena;
michael@0:       gStackArena = nullptr;
michael@0:     }
michael@0:   }
michael@0: 
michael@0:   static void* Allocate(size_t aSize) {
michael@0:     return gStackArena->Allocate(aSize);
michael@0:   }
michael@0: 
michael@0: private:
michael@0:   static StackArena* gStackArena;
michael@0:   bool mOwnsStackArena;
michael@0: };
michael@0: 
michael@0: } // namespace mozilla
michael@0: 
michael@0: #endif