src/gpu/GrBufferAllocPool.cpp - platform/external/skia - Gitiles


 /*
  * Copyright 2010 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */


 #include "GrBufferAllocPool.h"
 #include "GrDrawTargetCaps.h"
 #include "GrGpu.h"
 #include "GrIndexBuffer.h"
 #include "GrTypes.h"
 #include "GrVertexBuffer.h"

 #include "SkTraceEvent.h"

 #ifdef SK_DEBUG
     #define VALIDATE validate
 #else
     static void VALIDATE(bool = false) {}
 #endif

 // page size
 #define GrBufferAllocPool_MIN_BLOCK_SIZE ((size_t)1 << 12)

 #define UNMAP_BUFFER(block)                                                               \
 do {                                                                                      \
     TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("skia.gpu"),                           \
                          "GrBufferAllocPool Unmapping Buffer",                            \
                          TRACE_EVENT_SCOPE_THREAD,                                        \
                          "percent_unwritten",                                             \
                          (float)((block).fBytesFree) / (block).fBuffer->gpuMemorySize()); \
     (block).fBuffer->unmap();                                                             \
 } while (false)

 GrBufferAllocPool::GrBufferAllocPool(GrGpu* gpu,
                                      BufferType bufferType,
                                      bool frequentResetHint,
                                      size_t blockSize,
                                      int preallocBufferCnt) :
         fBlocks(SkTMax(8, 2*preallocBufferCnt)) {

     SkASSERT(gpu);
     fGpu = gpu;
     fGpu->ref();
     fGpuIsReffed = true;

     fBufferType = bufferType;
     fFrequentResetHint = frequentResetHint;
     fBufferPtr = NULL;
     fMinBlockSize = SkTMax(GrBufferAllocPool_MIN_BLOCK_SIZE, blockSize);

     fBytesInUse = 0;

     fPreallocBuffersInUse = 0;
     fPreallocBufferStartIdx = 0;
     for (int i = 0; i < preallocBufferCnt; ++i) {
         GrGeometryBuffer* buffer = this->createBuffer(fMinBlockSize);
         if (buffer) {
             *fPreallocBuffers.append() = buffer;
         }
     }
 }

 GrBufferAllocPool::~GrBufferAllocPool() {
     VALIDATE();
     if (fBlocks.count()) {
         GrGeometryBuffer* buffer = fBlocks.back().fBuffer;
         if (buffer->isMapped()) {
             UNMAP_BUFFER(fBlocks.back());
         }
     }
     while (!fBlocks.empty()) {
         destroyBlock();
     }
     fPreallocBuffers.unrefAll();
     releaseGpuRef();
 }

 void GrBufferAllocPool::releaseGpuRef() {
     if (fGpuIsReffed) {
         fGpu->unref();
         fGpuIsReffed = false;
     }
 }

 void GrBufferAllocPool::reset() {
     VALIDATE();
     fBytesInUse = 0;
     if (fBlocks.count()) {
         GrGeometryBuffer* buffer = fBlocks.back().fBuffer;
         if (buffer->isMapped()) {
             UNMAP_BUFFER(fBlocks.back());
         }
     }
     // fPreallocBuffersInUse will be decremented down to zero in the while loop
     int preallocBuffersInUse = fPreallocBuffersInUse;
     while (!fBlocks.empty()) {
         this->destroyBlock();
     }
     if (fPreallocBuffers.count()) {
         // must set this after above loop.
         fPreallocBufferStartIdx = (fPreallocBufferStartIdx +
                                    preallocBuffersInUse) %
                                   fPreallocBuffers.count();
     }
     // we may have created a large cpu mirror of a large VB. Reset the size
     // to match our pre-allocated VBs.
     fCpuData.reset(fMinBlockSize);
     SkASSERT(0 == fPreallocBuffersInUse);
     VALIDATE();
 }

 void GrBufferAllocPool::unmap() {
     VALIDATE();

     if (fBufferPtr) {
         BufferBlock& block = fBlocks.back();
         if (block.fBuffer->isMapped()) {
             UNMAP_BUFFER(block);
         } else {
             size_t flushSize = block.fBuffer->gpuMemorySize() - block.fBytesFree;
             this->flushCpuData(fBlocks.back(), flushSize);
         }
         fBufferPtr = NULL;
     }
     VALIDATE();
 }

 #ifdef SK_DEBUG
 void GrBufferAllocPool::validate(bool unusedBlockAllowed) const {
     if (fBufferPtr) {
         SkASSERT(!fBlocks.empty());
         if (fBlocks.back().fBuffer->isMapped()) {
             GrGeometryBuffer* buf = fBlocks.back().fBuffer;
             SkASSERT(buf->mapPtr() == fBufferPtr);
         } else {
             SkASSERT(fCpuData.get() == fBufferPtr);
         }
     } else {
         SkASSERT(fBlocks.empty() || !fBlocks.back().fBuffer->isMapped());
     }
     size_t bytesInUse = 0;
     for (int i = 0; i < fBlocks.count() - 1; ++i) {
         SkASSERT(!fBlocks[i].fBuffer->isMapped());
     }
     for (int i = 0; i < fBlocks.count(); ++i) {
         size_t bytes = fBlocks[i].fBuffer->gpuMemorySize() - fBlocks[i].fBytesFree;
         bytesInUse += bytes;
         SkASSERT(bytes || unusedBlockAllowed);
     }

     SkASSERT(bytesInUse == fBytesInUse);
     if (unusedBlockAllowed) {
         SkASSERT((fBytesInUse && !fBlocks.empty()) ||
                  (!fBytesInUse && (fBlocks.count() < 2)));
     } else {
         SkASSERT((0 == fBytesInUse) == fBlocks.empty());
     }
 }
 #endif

 void* GrBufferAllocPool::makeSpace(size_t size,
                                    size_t alignment,
                                    const GrGeometryBuffer** buffer,
                                    size_t* offset) {
     VALIDATE();

     SkASSERT(buffer);
     SkASSERT(offset);

     if (fBufferPtr) {
         BufferBlock& back = fBlocks.back();
         size_t usedBytes = back.fBuffer->gpuMemorySize() - back.fBytesFree;
         size_t pad = GrSizeAlignUpPad(usedBytes,
                                       alignment);
         if ((size + pad) <= back.fBytesFree) {
             usedBytes += pad;
             *offset = usedBytes;
             *buffer = back.fBuffer;
             back.fBytesFree -= size + pad;
             fBytesInUse += size + pad;
             VALIDATE();
             return (void*)(reinterpret_cast<intptr_t>(fBufferPtr) + usedBytes);
         }
     }

     // We could honor the space request using by a partial update of the current
     // VB (if there is room). But we don't currently use draw calls to GL that
     // allow the driver to know that previously issued draws won't read from
     // the part of the buffer we update. Also, the GL buffer implementation
     // may be cheating on the actual buffer size by shrinking the buffer on
     // updateData() if the amount of data passed is less than the full buffer
     // size.

     if (!createBlock(size)) {
         return NULL;
     }
     SkASSERT(fBufferPtr);

     *offset = 0;
     BufferBlock& back = fBlocks.back();
     *buffer = back.fBuffer;
     back.fBytesFree -= size;
     fBytesInUse += size;
     VALIDATE();
     return fBufferPtr;
 }

 int GrBufferAllocPool::currentBufferItems(size_t itemSize) const {
     VALIDATE();
     if (fBufferPtr) {
         const BufferBlock& back = fBlocks.back();
         size_t usedBytes = back.fBuffer->gpuMemorySize() - back.fBytesFree;
         size_t pad = GrSizeAlignUpPad(usedBytes, itemSize);
         return static_cast<int>((back.fBytesFree - pad) / itemSize);
     } else if (fPreallocBuffersInUse < fPreallocBuffers.count()) {
         return static_cast<int>(fMinBlockSize / itemSize);
     }
     return 0;
 }

 int GrBufferAllocPool::preallocatedBuffersRemaining() const {
     return fPreallocBuffers.count() - fPreallocBuffersInUse;
 }

 int GrBufferAllocPool::preallocatedBufferCount() const {
     return fPreallocBuffers.count();
 }

 void GrBufferAllocPool::putBack(size_t bytes) {
     VALIDATE();

     // if the putBack unwinds all the preallocated buffers then we will
     // advance the starting index. As blocks are destroyed fPreallocBuffersInUse
     // will be decremented. I will reach zero if all blocks using preallocated
     // buffers are released.
     int preallocBuffersInUse = fPreallocBuffersInUse;

     while (bytes) {
         // caller shouldnt try to put back more than they've taken
         SkASSERT(!fBlocks.empty());
         BufferBlock& block = fBlocks.back();
         size_t bytesUsed = block.fBuffer->gpuMemorySize() - block.fBytesFree;
         if (bytes >= bytesUsed) {
             bytes -= bytesUsed;
             fBytesInUse -= bytesUsed;
             // if we locked a vb to satisfy the make space and we're releasing
             // beyond it, then unmap it.
             if (block.fBuffer->isMapped()) {
                 UNMAP_BUFFER(block);
             }
             this->destroyBlock();
         } else {
             block.fBytesFree += bytes;
             fBytesInUse -= bytes;
             bytes = 0;
             break;
         }
     }
     if (!fPreallocBuffersInUse && fPreallocBuffers.count()) {
             fPreallocBufferStartIdx = (fPreallocBufferStartIdx +
                                        preallocBuffersInUse) %
                                       fPreallocBuffers.count();
     }
     VALIDATE();
 }

 bool GrBufferAllocPool::createBlock(size_t requestSize) {

     size_t size = SkTMax(requestSize, fMinBlockSize);
     SkASSERT(size >= GrBufferAllocPool_MIN_BLOCK_SIZE);

     VALIDATE();

     BufferBlock& block = fBlocks.push_back();

     if (size == fMinBlockSize &&
         fPreallocBuffersInUse < fPreallocBuffers.count()) {

         uint32_t nextBuffer = (fPreallocBuffersInUse +
                                fPreallocBufferStartIdx) %
                               fPreallocBuffers.count();
         block.fBuffer = fPreallocBuffers[nextBuffer];
         block.fBuffer->ref();
         ++fPreallocBuffersInUse;
     } else {
         block.fBuffer = this->createBuffer(size);
         if (NULL == block.fBuffer) {
             fBlocks.pop_back();
             return false;
         }
     }

     block.fBytesFree = size;
     if (fBufferPtr) {
         SkASSERT(fBlocks.count() > 1);
         BufferBlock& prev = fBlocks.fromBack(1);
         if (prev.fBuffer->isMapped()) {
             UNMAP_BUFFER(prev);
         } else {
             this->flushCpuData(prev, prev.fBuffer->gpuMemorySize() - prev.fBytesFree);
         }
         fBufferPtr = NULL;
     }

     SkASSERT(NULL == fBufferPtr);

     // If the buffer is CPU-backed we map it because it is free to do so and saves a copy.
     // Otherwise when buffer mapping is supported:
     //      a) If the frequently reset hint is set we only map when the requested size meets a
     //      threshold (since we don't expect it is likely that we will see more vertex data)
     //      b) If the hint is not set we map if the buffer size is greater than the threshold.
     bool attemptMap = block.fBuffer->isCPUBacked();
     if (!attemptMap && GrDrawTargetCaps::kNone_MapFlags != fGpu->caps()->mapBufferFlags()) {
         if (fFrequentResetHint) {
             attemptMap = requestSize > GR_GEOM_BUFFER_MAP_THRESHOLD;
         } else {
             attemptMap = size > GR_GEOM_BUFFER_MAP_THRESHOLD;
         }
     }

     if (attemptMap) {
         fBufferPtr = block.fBuffer->map();
     }

     if (NULL == fBufferPtr) {
         fBufferPtr = fCpuData.reset(size);
     }

     VALIDATE(true);

     return true;
 }

 void GrBufferAllocPool::destroyBlock() {
     SkASSERT(!fBlocks.empty());

     BufferBlock& block = fBlocks.back();
     if (fPreallocBuffersInUse > 0) {
         uint32_t prevPreallocBuffer = (fPreallocBuffersInUse +
                                        fPreallocBufferStartIdx +
                                        (fPreallocBuffers.count() - 1)) %
                                       fPreallocBuffers.count();
         if (block.fBuffer == fPreallocBuffers[prevPreallocBuffer]) {
             --fPreallocBuffersInUse;
         }
     }
     SkASSERT(!block.fBuffer->isMapped());
     block.fBuffer->unref();
     fBlocks.pop_back();
     fBufferPtr = NULL;
 }

 void GrBufferAllocPool::flushCpuData(const BufferBlock& block, size_t flushSize) {
     GrGeometryBuffer* buffer = block.fBuffer;
     SkASSERT(buffer);
     SkASSERT(!buffer->isMapped());
     SkASSERT(fCpuData.get() == fBufferPtr);
     SkASSERT(flushSize <= buffer->gpuMemorySize());
     VALIDATE(true);

     if (GrDrawTargetCaps::kNone_MapFlags != fGpu->caps()->mapBufferFlags() &&
         flushSize > GR_GEOM_BUFFER_MAP_THRESHOLD) {
         void* data = buffer->map();
         if (data) {
             memcpy(data, fBufferPtr, flushSize);
             UNMAP_BUFFER(block);
             return;
         }
     }
     buffer->updateData(fBufferPtr, flushSize);
     VALIDATE(true);
 }

 GrGeometryBuffer* GrBufferAllocPool::createBuffer(size_t size) {
     if (kIndex_BufferType == fBufferType) {
         return fGpu->createIndexBuffer(size, true);
     } else {
         SkASSERT(kVertex_BufferType == fBufferType);
         return fGpu->createVertexBuffer(size, true);
     }
 }

 ////////////////////////////////////////////////////////////////////////////////

 GrVertexBufferAllocPool::GrVertexBufferAllocPool(GrGpu* gpu,
                                                  bool frequentResetHint,
                                                  size_t bufferSize,
                                                  int preallocBufferCnt)
 : GrBufferAllocPool(gpu,
                     kVertex_BufferType,
                     frequentResetHint,
                     bufferSize,
                     preallocBufferCnt) {
 }

 void* GrVertexBufferAllocPool::makeSpace(size_t vertexSize,
                                          int vertexCount,
                                          const GrVertexBuffer** buffer,
                                          int* startVertex) {

     SkASSERT(vertexCount >= 0);
     SkASSERT(buffer);
     SkASSERT(startVertex);

     size_t offset = 0; // assign to suppress warning
     const GrGeometryBuffer* geomBuffer = NULL; // assign to suppress warning
     void* ptr = INHERITED::makeSpace(vertexSize * vertexCount,
                                      vertexSize,
                                      &geomBuffer,
                                      &offset);

     *buffer = (const GrVertexBuffer*) geomBuffer;
     SkASSERT(0 == offset % vertexSize);
     *startVertex = static_cast<int>(offset / vertexSize);
     return ptr;
 }

 bool GrVertexBufferAllocPool::appendVertices(size_t vertexSize,
                                              int vertexCount,
                                              const void* vertices,
                                              const GrVertexBuffer** buffer,
                                              int* startVertex) {
     void* space = makeSpace(vertexSize, vertexCount, buffer, startVertex);
     if (space) {
         memcpy(space,
                vertices,
                vertexSize * vertexCount);
         return true;
     } else {
         return false;
     }
 }

 int GrVertexBufferAllocPool::preallocatedBufferVertices(size_t vertexSize) const {
     return static_cast<int>(INHERITED::preallocatedBufferSize() / vertexSize);
 }

 int GrVertexBufferAllocPool::currentBufferVertices(size_t vertexSize) const {
     return currentBufferItems(vertexSize);
 }

 ////////////////////////////////////////////////////////////////////////////////

 GrIndexBufferAllocPool::GrIndexBufferAllocPool(GrGpu* gpu,
                                                bool frequentResetHint,
                                                size_t bufferSize,
                                                int preallocBufferCnt)
 : GrBufferAllocPool(gpu,
                     kIndex_BufferType,
                     frequentResetHint,
                     bufferSize,
                     preallocBufferCnt) {
 }

 void* GrIndexBufferAllocPool::makeSpace(int indexCount,
                                         const GrIndexBuffer** buffer,
                                         int* startIndex) {

     SkASSERT(indexCount >= 0);
     SkASSERT(buffer);
     SkASSERT(startIndex);

     size_t offset = 0; // assign to suppress warning
     const GrGeometryBuffer* geomBuffer = NULL; // assign to suppress warning
     void* ptr = INHERITED::makeSpace(indexCount * sizeof(uint16_t),
                                      sizeof(uint16_t),
                                      &geomBuffer,
                                      &offset);

     *buffer = (const GrIndexBuffer*) geomBuffer;
     SkASSERT(0 == offset % sizeof(uint16_t));
     *startIndex = static_cast<int>(offset / sizeof(uint16_t));
     return ptr;
 }

 bool GrIndexBufferAllocPool::appendIndices(int indexCount,
                                            const void* indices,
                                            const GrIndexBuffer** buffer,
                                            int* startIndex) {
     void* space = makeSpace(indexCount, buffer, startIndex);
     if (space) {
         memcpy(space, indices, sizeof(uint16_t) * indexCount);
         return true;
     } else {
         return false;
     }
 }

 int GrIndexBufferAllocPool::preallocatedBufferIndices() const {
     return static_cast<int>(INHERITED::preallocatedBufferSize() / sizeof(uint16_t));
 }

 int GrIndexBufferAllocPool::currentBufferIndices() const {
     return currentBufferItems(sizeof(uint16_t));
 }

	/*
	* Copyright 2010 Google Inc.
	*
	* Use of this source code is governed by a BSD-style license that can be
	* found in the LICENSE file.
	*/


	#include "GrBufferAllocPool.h"
	#include "GrDrawTargetCaps.h"
	#include "GrGpu.h"
	#include "GrIndexBuffer.h"
	#include "GrTypes.h"
	#include "GrVertexBuffer.h"

	#include "SkTraceEvent.h"

	#ifdef SK_DEBUG
	#define VALIDATE validate
	#else
	static void VALIDATE(bool = false) {}
	#endif

	// page size
	#define GrBufferAllocPool_MIN_BLOCK_SIZE ((size_t)1 << 12)

	#define UNMAP_BUFFER(block) \
	do { \
	TRACE_EVENT_INSTANT1(TRACE_DISABLED_BY_DEFAULT("skia.gpu"), \
	"GrBufferAllocPool Unmapping Buffer", \
	TRACE_EVENT_SCOPE_THREAD, \
	"percent_unwritten", \
	(float)((block).fBytesFree) / (block).fBuffer->gpuMemorySize()); \
	(block).fBuffer->unmap(); \
	} while (false)

	GrBufferAllocPool::GrBufferAllocPool(GrGpu* gpu,
	BufferType bufferType,
	bool frequentResetHint,
	size_t blockSize,
	int preallocBufferCnt) :
	fBlocks(SkTMax(8, 2*preallocBufferCnt)) {

	SkASSERT(gpu);
	fGpu = gpu;
	fGpu->ref();
	fGpuIsReffed = true;

	fBufferType = bufferType;
	fFrequentResetHint = frequentResetHint;
	fBufferPtr = NULL;
	fMinBlockSize = SkTMax(GrBufferAllocPool_MIN_BLOCK_SIZE, blockSize);

	fBytesInUse = 0;

	fPreallocBuffersInUse = 0;
	fPreallocBufferStartIdx = 0;
	for (int i = 0; i < preallocBufferCnt; ++i) {
	GrGeometryBuffer* buffer = this->createBuffer(fMinBlockSize);
	if (buffer) {
	*fPreallocBuffers.append() = buffer;
	}
	}
	}

	GrBufferAllocPool::~GrBufferAllocPool() {
	VALIDATE();
	if (fBlocks.count()) {
	GrGeometryBuffer* buffer = fBlocks.back().fBuffer;
	if (buffer->isMapped()) {
	UNMAP_BUFFER(fBlocks.back());
	}
	}
	while (!fBlocks.empty()) {
	destroyBlock();
	}
	fPreallocBuffers.unrefAll();
	releaseGpuRef();
	}

	void GrBufferAllocPool::releaseGpuRef() {
	if (fGpuIsReffed) {
	fGpu->unref();
	fGpuIsReffed = false;
	}
	}

	void GrBufferAllocPool::reset() {
	VALIDATE();
	fBytesInUse = 0;
	if (fBlocks.count()) {
	GrGeometryBuffer* buffer = fBlocks.back().fBuffer;
	if (buffer->isMapped()) {
	UNMAP_BUFFER(fBlocks.back());
	}
	}
	// fPreallocBuffersInUse will be decremented down to zero in the while loop
	int preallocBuffersInUse = fPreallocBuffersInUse;
	while (!fBlocks.empty()) {
	this->destroyBlock();
	}
	if (fPreallocBuffers.count()) {
	// must set this after above loop.
	fPreallocBufferStartIdx = (fPreallocBufferStartIdx +
	preallocBuffersInUse) %
	fPreallocBuffers.count();
	}
	// we may have created a large cpu mirror of a large VB. Reset the size
	// to match our pre-allocated VBs.
	fCpuData.reset(fMinBlockSize);
	SkASSERT(0 == fPreallocBuffersInUse);
	VALIDATE();
	}

	void GrBufferAllocPool::unmap() {
	VALIDATE();

	if (fBufferPtr) {
	BufferBlock& block = fBlocks.back();
	if (block.fBuffer->isMapped()) {
	UNMAP_BUFFER(block);
	} else {
	size_t flushSize = block.fBuffer->gpuMemorySize() - block.fBytesFree;
	this->flushCpuData(fBlocks.back(), flushSize);
	}
	fBufferPtr = NULL;
	}
	VALIDATE();
	}

	#ifdef SK_DEBUG
	void GrBufferAllocPool::validate(bool unusedBlockAllowed) const {
	if (fBufferPtr) {
	SkASSERT(!fBlocks.empty());
	if (fBlocks.back().fBuffer->isMapped()) {
	GrGeometryBuffer* buf = fBlocks.back().fBuffer;
	SkASSERT(buf->mapPtr() == fBufferPtr);
	} else {
	SkASSERT(fCpuData.get() == fBufferPtr);
	}
	} else {
	SkASSERT(fBlocks.empty() \|\| !fBlocks.back().fBuffer->isMapped());
	}
	size_t bytesInUse = 0;
	for (int i = 0; i < fBlocks.count() - 1; ++i) {
	SkASSERT(!fBlocks[i].fBuffer->isMapped());
	}
	for (int i = 0; i < fBlocks.count(); ++i) {
	size_t bytes = fBlocks[i].fBuffer->gpuMemorySize() - fBlocks[i].fBytesFree;
	bytesInUse += bytes;
	SkASSERT(bytes \|\| unusedBlockAllowed);
	}

	SkASSERT(bytesInUse == fBytesInUse);
	if (unusedBlockAllowed) {
	SkASSERT((fBytesInUse && !fBlocks.empty()) \|\|
	(!fBytesInUse && (fBlocks.count() < 2)));
	} else {
	SkASSERT((0 == fBytesInUse) == fBlocks.empty());
	}
	}
	#endif

	void* GrBufferAllocPool::makeSpace(size_t size,
	size_t alignment,
	const GrGeometryBuffer** buffer,
	size_t* offset) {
	VALIDATE();

	SkASSERT(buffer);
	SkASSERT(offset);

	if (fBufferPtr) {
	BufferBlock& back = fBlocks.back();
	size_t usedBytes = back.fBuffer->gpuMemorySize() - back.fBytesFree;
	size_t pad = GrSizeAlignUpPad(usedBytes,
	alignment);
	if ((size + pad) <= back.fBytesFree) {
	usedBytes += pad;
	*offset = usedBytes;
	*buffer = back.fBuffer;
	back.fBytesFree -= size + pad;
	fBytesInUse += size + pad;
	VALIDATE();
	return (void*)(reinterpret_cast<intptr_t>(fBufferPtr) + usedBytes);
	}
	}

	// We could honor the space request using by a partial update of the current
	// VB (if there is room). But we don't currently use draw calls to GL that
	// allow the driver to know that previously issued draws won't read from
	// the part of the buffer we update. Also, the GL buffer implementation
	// may be cheating on the actual buffer size by shrinking the buffer on
	// updateData() if the amount of data passed is less than the full buffer
	// size.

	if (!createBlock(size)) {
	return NULL;
	}
	SkASSERT(fBufferPtr);

	*offset = 0;
	BufferBlock& back = fBlocks.back();
	*buffer = back.fBuffer;
	back.fBytesFree -= size;
	fBytesInUse += size;
	VALIDATE();
	return fBufferPtr;
	}

	int GrBufferAllocPool::currentBufferItems(size_t itemSize) const {
	VALIDATE();
	if (fBufferPtr) {
	const BufferBlock& back = fBlocks.back();
	size_t usedBytes = back.fBuffer->gpuMemorySize() - back.fBytesFree;
	size_t pad = GrSizeAlignUpPad(usedBytes, itemSize);
	return static_cast<int>((back.fBytesFree - pad) / itemSize);
	} else if (fPreallocBuffersInUse < fPreallocBuffers.count()) {
	return static_cast<int>(fMinBlockSize / itemSize);
	}
	return 0;
	}

	int GrBufferAllocPool::preallocatedBuffersRemaining() const {
	return fPreallocBuffers.count() - fPreallocBuffersInUse;
	}

	int GrBufferAllocPool::preallocatedBufferCount() const {
	return fPreallocBuffers.count();
	}

	void GrBufferAllocPool::putBack(size_t bytes) {
	VALIDATE();

	// if the putBack unwinds all the preallocated buffers then we will
	// advance the starting index. As blocks are destroyed fPreallocBuffersInUse
	// will be decremented. I will reach zero if all blocks using preallocated
	// buffers are released.
	int preallocBuffersInUse = fPreallocBuffersInUse;

	while (bytes) {
	// caller shouldnt try to put back more than they've taken
	SkASSERT(!fBlocks.empty());
	BufferBlock& block = fBlocks.back();
	size_t bytesUsed = block.fBuffer->gpuMemorySize() - block.fBytesFree;
	if (bytes >= bytesUsed) {
	bytes -= bytesUsed;
	fBytesInUse -= bytesUsed;
	// if we locked a vb to satisfy the make space and we're releasing
	// beyond it, then unmap it.
	if (block.fBuffer->isMapped()) {
	UNMAP_BUFFER(block);
	}
	this->destroyBlock();
	} else {
	block.fBytesFree += bytes;
	fBytesInUse -= bytes;
	bytes = 0;
	break;
	}
	}
	if (!fPreallocBuffersInUse && fPreallocBuffers.count()) {
	fPreallocBufferStartIdx = (fPreallocBufferStartIdx +
	preallocBuffersInUse) %
	fPreallocBuffers.count();
	}
	VALIDATE();
	}

	bool GrBufferAllocPool::createBlock(size_t requestSize) {

	size_t size = SkTMax(requestSize, fMinBlockSize);
	SkASSERT(size >= GrBufferAllocPool_MIN_BLOCK_SIZE);

	VALIDATE();

	BufferBlock& block = fBlocks.push_back();

	if (size == fMinBlockSize &&
	fPreallocBuffersInUse < fPreallocBuffers.count()) {

	uint32_t nextBuffer = (fPreallocBuffersInUse +
	fPreallocBufferStartIdx) %
	fPreallocBuffers.count();
	block.fBuffer = fPreallocBuffers[nextBuffer];
	block.fBuffer->ref();
	++fPreallocBuffersInUse;
	} else {
	block.fBuffer = this->createBuffer(size);
	if (NULL == block.fBuffer) {
	fBlocks.pop_back();
	return false;
	}
	}

	block.fBytesFree = size;
	if (fBufferPtr) {
	SkASSERT(fBlocks.count() > 1);
	BufferBlock& prev = fBlocks.fromBack(1);
	if (prev.fBuffer->isMapped()) {
	UNMAP_BUFFER(prev);
	} else {
	this->flushCpuData(prev, prev.fBuffer->gpuMemorySize() - prev.fBytesFree);
	}
	fBufferPtr = NULL;
	}

	SkASSERT(NULL == fBufferPtr);

	// If the buffer is CPU-backed we map it because it is free to do so and saves a copy.
	// Otherwise when buffer mapping is supported:
	// a) If the frequently reset hint is set we only map when the requested size meets a
	// threshold (since we don't expect it is likely that we will see more vertex data)
	// b) If the hint is not set we map if the buffer size is greater than the threshold.
	bool attemptMap = block.fBuffer->isCPUBacked();
	if (!attemptMap && GrDrawTargetCaps::kNone_MapFlags != fGpu->caps()->mapBufferFlags()) {
	if (fFrequentResetHint) {
	attemptMap = requestSize > GR_GEOM_BUFFER_MAP_THRESHOLD;
	} else {
	attemptMap = size > GR_GEOM_BUFFER_MAP_THRESHOLD;
	}
	}

	if (attemptMap) {
	fBufferPtr = block.fBuffer->map();
	}

	if (NULL == fBufferPtr) {
	fBufferPtr = fCpuData.reset(size);
	}

	VALIDATE(true);

	return true;
	}

	void GrBufferAllocPool::destroyBlock() {
	SkASSERT(!fBlocks.empty());

	BufferBlock& block = fBlocks.back();
	if (fPreallocBuffersInUse > 0) {
	uint32_t prevPreallocBuffer = (fPreallocBuffersInUse +
	fPreallocBufferStartIdx +
	(fPreallocBuffers.count() - 1)) %
	fPreallocBuffers.count();
	if (block.fBuffer == fPreallocBuffers[prevPreallocBuffer]) {
	--fPreallocBuffersInUse;
	}
	}
	SkASSERT(!block.fBuffer->isMapped());
	block.fBuffer->unref();
	fBlocks.pop_back();
	fBufferPtr = NULL;
	}

	void GrBufferAllocPool::flushCpuData(const BufferBlock& block, size_t flushSize) {
	GrGeometryBuffer* buffer = block.fBuffer;
	SkASSERT(buffer);
	SkASSERT(!buffer->isMapped());
	SkASSERT(fCpuData.get() == fBufferPtr);
	SkASSERT(flushSize <= buffer->gpuMemorySize());
	VALIDATE(true);

	if (GrDrawTargetCaps::kNone_MapFlags != fGpu->caps()->mapBufferFlags() &&
	flushSize > GR_GEOM_BUFFER_MAP_THRESHOLD) {
	void* data = buffer->map();
	if (data) {
	memcpy(data, fBufferPtr, flushSize);
	UNMAP_BUFFER(block);
	return;
	}
	}
	buffer->updateData(fBufferPtr, flushSize);
	VALIDATE(true);
	}

	GrGeometryBuffer* GrBufferAllocPool::createBuffer(size_t size) {
	if (kIndex_BufferType == fBufferType) {
	return fGpu->createIndexBuffer(size, true);
	} else {
	SkASSERT(kVertex_BufferType == fBufferType);
	return fGpu->createVertexBuffer(size, true);
	}
	}

	////////////////////////////////////////////////////////////////////////////////

	GrVertexBufferAllocPool::GrVertexBufferAllocPool(GrGpu* gpu,
	bool frequentResetHint,
	size_t bufferSize,
	int preallocBufferCnt)
	: GrBufferAllocPool(gpu,
	kVertex_BufferType,
	frequentResetHint,
	bufferSize,
	preallocBufferCnt) {
	}

	void* GrVertexBufferAllocPool::makeSpace(size_t vertexSize,
	int vertexCount,
	const GrVertexBuffer** buffer,
	int* startVertex) {

	SkASSERT(vertexCount >= 0);
	SkASSERT(buffer);
	SkASSERT(startVertex);

	size_t offset = 0; // assign to suppress warning
	const GrGeometryBuffer* geomBuffer = NULL; // assign to suppress warning
	void* ptr = INHERITED::makeSpace(vertexSize * vertexCount,
	vertexSize,
	&geomBuffer,
	&offset);

	buffer = (const GrVertexBuffer) geomBuffer;
	SkASSERT(0 == offset % vertexSize);
	*startVertex = static_cast<int>(offset / vertexSize);
	return ptr;
	}

	bool GrVertexBufferAllocPool::appendVertices(size_t vertexSize,
	int vertexCount,
	const void* vertices,
	const GrVertexBuffer** buffer,
	int* startVertex) {
	void* space = makeSpace(vertexSize, vertexCount, buffer, startVertex);
	if (space) {
	memcpy(space,
	vertices,
	vertexSize * vertexCount);
	return true;
	} else {
	return false;
	}
	}

	int GrVertexBufferAllocPool::preallocatedBufferVertices(size_t vertexSize) const {
	return static_cast<int>(INHERITED::preallocatedBufferSize() / vertexSize);
	}

	int GrVertexBufferAllocPool::currentBufferVertices(size_t vertexSize) const {
	return currentBufferItems(vertexSize);
	}

	////////////////////////////////////////////////////////////////////////////////

	GrIndexBufferAllocPool::GrIndexBufferAllocPool(GrGpu* gpu,
	bool frequentResetHint,
	size_t bufferSize,
	int preallocBufferCnt)
	: GrBufferAllocPool(gpu,
	kIndex_BufferType,
	frequentResetHint,
	bufferSize,
	preallocBufferCnt) {
	}

	void* GrIndexBufferAllocPool::makeSpace(int indexCount,
	const GrIndexBuffer** buffer,
	int* startIndex) {

	SkASSERT(indexCount >= 0);
	SkASSERT(buffer);
	SkASSERT(startIndex);

	size_t offset = 0; // assign to suppress warning
	const GrGeometryBuffer* geomBuffer = NULL; // assign to suppress warning
	void* ptr = INHERITED::makeSpace(indexCount * sizeof(uint16_t),
	sizeof(uint16_t),
	&geomBuffer,
	&offset);

	buffer = (const GrIndexBuffer) geomBuffer;
	SkASSERT(0 == offset % sizeof(uint16_t));
	*startIndex = static_cast<int>(offset / sizeof(uint16_t));
	return ptr;
	}

	bool GrIndexBufferAllocPool::appendIndices(int indexCount,
	const void* indices,
	const GrIndexBuffer** buffer,
	int* startIndex) {
	void* space = makeSpace(indexCount, buffer, startIndex);
	if (space) {
	memcpy(space, indices, sizeof(uint16_t) * indexCount);
	return true;
	} else {
	return false;
	}
	}

	int GrIndexBufferAllocPool::preallocatedBufferIndices() const {
	return static_cast<int>(INHERITED::preallocatedBufferSize() / sizeof(uint16_t));
	}

	int GrIndexBufferAllocPool::currentBufferIndices() const {
	return currentBufferItems(sizeof(uint16_t));
	}