PxcScratchAllocator.h

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// Copyright (c) 2001-2004 NovodeX AG. All rights reserved.

// Copyright (c) 2004-2008 AGEIA Technologies, Inc. All rights reserved.

// SPDX-FileCopyrightText: Copyright (c) 2008-2026 NVIDIA CORPORATION & AFFILIATES. All rights reserved.

// SPDX-License-Identifier: Apache-2.0

#ifndef PXC_SCRATCH_ALLOCATOR_H

#define PXC_SCRATCH_ALLOCATOR_H

#include "foundation/PxAssert.h"

#include "PxPhysXConfig.h"

#include "foundation/PxMutex.h"

#include "foundation/PxArray.h"

#include "foundation/PxAllocator.h"

#include "foundation/PxUserAllocated.h"

namespace physx

class PxcScratchAllocator : public PxUserAllocated

	PX_NOCOPY(PxcScratchAllocator)

public:

	PxcScratchAllocator() : mStack("PxcScratchAllocator"), mStart(NULL), mSize(0)

		mStack.reserve(64);

		mStack.pushBack(0);

	void setBlock(void* addr, PxU32 size)

		PX_ASSERT(!(size&15));

		// if the stack is not empty then some scratch memory was not freed on the previous frame. That's

		// likely indicative of a problem, because when the scratch block is too small the memory will have

		// come from the heap

		PX_ASSERT(mStack.size()==1);

		mStack.popBack();

		mStart = reinterpret_cast<PxU8*>(addr);

		mSize = size;

		mStack.pushBack(mStart + size);

	void* allocAll(PxU32& size)

		PxMutex::ScopedLock lock(mLock);

		PX_ASSERT(mStack.size()>0);

		size = PxU32(mStack.back()-mStart);

		if(size==0)

			return NULL;

		mStack.pushBack(mStart);

		return mStart;

	void* alloc(PxU32 requestedSize, bool fallBackToHeap = false)

		requestedSize = (requestedSize+15)&~15;

		PxMutex::ScopedLock lock(mLock);

		PX_ASSERT(mStack.size()>=1);

		PxU8* top = mStack.back();

		if(top - mStart >= ptrdiff_t(requestedSize))

			PxU8* addr = top - requestedSize;

			mStack.pushBack(addr);

			return addr;

		if(!fallBackToHeap)

			return NULL;

		return PX_ALLOC(requestedSize, "Scratch Block Fallback");

	void free(void* addr)

		PX_ASSERT(addr!=NULL);

		if(!isScratchAddr(addr))

			PX_FREE(addr);

			return;

		PxMutex::ScopedLock lock(mLock);

		PX_ASSERT(mStack.size()>1);

		PxU32 i=mStack.size()-1;

		while(mStack[i]<addr)

			i--;

		PX_ASSERT(mStack[i]==addr);

		mStack.remove(i);

	bool isScratchAddr(void* addr) const

		PxU8* a = reinterpret_cast<PxU8*>(addr);

		return a>= mStart && a<mStart+mSize;

private:

	PxMutex				mLock;

	PxArray<PxU8*>		mStack;

	PxU8*				mStart;

	PxU32				mSize;

};

#endif