xref: /aosp_15_r20/external/skia/src/gpu/ganesh/GrBufferAllocPool.cpp (revision c8dee2aa9b3f27cf6c858bd81872bdeb2c07ed17)
1 /*
2  * Copyright 2010 Google Inc.
3  *
4  * Use of this source code is governed by a BSD-style license that can be
5  * found in the LICENSE file.
6  */
7 #include "src/gpu/ganesh/GrBufferAllocPool.h"
8 
9 #include "include/gpu/ganesh/GrDirectContext.h"
10 #include "include/private/base/SkMacros.h"
11 #include "src/base/SkSafeMath.h"
12 #include "src/core/SkTraceEvent.h"
13 #include "src/gpu/ganesh/GrCaps.h"
14 #include "src/gpu/ganesh/GrCpuBuffer.h"
15 #include "src/gpu/ganesh/GrDirectContextPriv.h"
16 #include "src/gpu/ganesh/GrGpu.h"
17 #include "src/gpu/ganesh/GrGpuBuffer.h"
18 #include "src/gpu/ganesh/GrResourceProvider.h"
19 
20 #include <algorithm>
21 #include <cstdint>
22 #include <cstring>
23 #include <memory>
24 
Make(int maxBuffersToCache)25 sk_sp<GrBufferAllocPool::CpuBufferCache> GrBufferAllocPool::CpuBufferCache::Make(
26         int maxBuffersToCache) {
27     return sk_sp<CpuBufferCache>(new CpuBufferCache(maxBuffersToCache));
28 }
29 
CpuBufferCache(int maxBuffersToCache)30 GrBufferAllocPool::CpuBufferCache::CpuBufferCache(int maxBuffersToCache)
31         : fMaxBuffersToCache(maxBuffersToCache) {
32     if (fMaxBuffersToCache) {
33         fBuffers = std::make_unique<Buffer[]>(fMaxBuffersToCache);
34     }
35 }
36 
makeBuffer(size_t size,bool mustBeInitialized)37 sk_sp<GrCpuBuffer> GrBufferAllocPool::CpuBufferCache::makeBuffer(size_t size,
38                                                                  bool mustBeInitialized) {
39     SkASSERT(size > 0);
40     Buffer* result = nullptr;
41     if (size == kDefaultBufferSize) {
42         int i = 0;
43         for (; i < fMaxBuffersToCache && fBuffers[i].fBuffer; ++i) {
44             SkASSERT(fBuffers[i].fBuffer->size() == kDefaultBufferSize);
45             if (fBuffers[i].fBuffer->unique()) {
46                 result = &fBuffers[i];
47             }
48         }
49         if (!result && i < fMaxBuffersToCache) {
50             fBuffers[i].fBuffer = GrCpuBuffer::Make(size);
51             result = &fBuffers[i];
52         }
53     }
54     Buffer tempResult;
55     if (!result) {
56         tempResult.fBuffer = GrCpuBuffer::Make(size);
57         result = &tempResult;
58     }
59     if (mustBeInitialized && !result->fCleared) {
60         result->fCleared = true;
61         memset(result->fBuffer->data(), 0, result->fBuffer->size());
62     }
63     return result->fBuffer;
64 }
65 
releaseAll()66 void GrBufferAllocPool::CpuBufferCache::releaseAll() {
67     for (int i = 0; i < fMaxBuffersToCache && fBuffers[i].fBuffer; ++i) {
68         fBuffers[i].fBuffer.reset();
69         fBuffers[i].fCleared = false;
70     }
71 }
72 
73 //////////////////////////////////////////////////////////////////////////////
74 
75 #ifdef SK_DEBUG
76     #define VALIDATE validate
77 #else
VALIDATE(bool=false)78     static void VALIDATE(bool = false) {}
79 #endif
80 
81 #define UNMAP_BUFFER(block)                                                          \
82     do {                                                                             \
83         TRACE_EVENT_INSTANT1("skia.gpu", "GrBufferAllocPool Unmapping Buffer",       \
84                              TRACE_EVENT_SCOPE_THREAD, "percent_unwritten",          \
85                              (float)((block).fBytesFree) / (block).fBuffer->size()); \
86         SkASSERT(!block.fBuffer->isCpuBuffer());                                     \
87         static_cast<GrGpuBuffer*>(block.fBuffer.get())->unmap();                     \
88     } while (false)
89 
GrBufferAllocPool(GrGpu * gpu,GrGpuBufferType bufferType,sk_sp<CpuBufferCache> cpuBufferCache)90 GrBufferAllocPool::GrBufferAllocPool(GrGpu* gpu, GrGpuBufferType bufferType,
91                                      sk_sp<CpuBufferCache> cpuBufferCache)
92         : fBlocks(8)
93         , fCpuBufferCache(std::move(cpuBufferCache))
94         , fGpu(gpu)
95         , fBufferType(bufferType) {}
96 
deleteBlocks()97 void GrBufferAllocPool::deleteBlocks() {
98     if (!fBlocks.empty()) {
99         GrBuffer* buffer = fBlocks.back().fBuffer.get();
100         if (!buffer->isCpuBuffer() && static_cast<GrGpuBuffer*>(buffer)->isMapped()) {
101             UNMAP_BUFFER(fBlocks.back());
102         }
103     }
104     while (!fBlocks.empty()) {
105         this->destroyBlock();
106     }
107     SkASSERT(!fBufferPtr);
108 }
109 
~GrBufferAllocPool()110 GrBufferAllocPool::~GrBufferAllocPool() {
111     VALIDATE();
112     this->deleteBlocks();
113 }
114 
reset()115 void GrBufferAllocPool::reset() {
116     VALIDATE();
117     fBytesInUse = 0;
118     this->deleteBlocks();
119     this->resetCpuData(0);
120     VALIDATE();
121 }
122 
unmap()123 void GrBufferAllocPool::unmap() {
124     VALIDATE();
125 
126     if (fBufferPtr) {
127         BufferBlock& block = fBlocks.back();
128         GrBuffer* buffer = block.fBuffer.get();
129         if (!buffer->isCpuBuffer()) {
130             if (static_cast<GrGpuBuffer*>(buffer)->isMapped()) {
131                 UNMAP_BUFFER(block);
132             } else {
133                 size_t flushSize = block.fBuffer->size() - block.fBytesFree;
134                 this->flushCpuData(fBlocks.back(), flushSize);
135             }
136         }
137         fBufferPtr = nullptr;
138     }
139     VALIDATE();
140 }
141 
142 #ifdef SK_DEBUG
validate(bool unusedBlockAllowed) const143 void GrBufferAllocPool::validate(bool unusedBlockAllowed) const {
144     bool wasDestroyed = false;
145     if (fBufferPtr) {
146         SkASSERT(!fBlocks.empty());
147         const GrBuffer* buffer = fBlocks.back().fBuffer.get();
148         if (!buffer->isCpuBuffer() && !static_cast<const GrGpuBuffer*>(buffer)->isMapped()) {
149             SkASSERT(fCpuStagingBuffer && fCpuStagingBuffer->data() == fBufferPtr);
150         }
151     } else if (!fBlocks.empty()) {
152         const GrBuffer* buffer = fBlocks.back().fBuffer.get();
153         SkASSERT(buffer->isCpuBuffer() || !static_cast<const GrGpuBuffer*>(buffer)->isMapped());
154     }
155     size_t bytesInUse = 0;
156     for (int i = 0; i < fBlocks.size() - 1; ++i) {
157         const GrBuffer* buffer = fBlocks[i].fBuffer.get();
158         SkASSERT(buffer->isCpuBuffer() || !static_cast<const GrGpuBuffer*>(buffer)->isMapped());
159     }
160     for (int i = 0; !wasDestroyed && i < fBlocks.size(); ++i) {
161         GrBuffer* buffer = fBlocks[i].fBuffer.get();
162         if (!buffer->isCpuBuffer() && static_cast<GrGpuBuffer*>(buffer)->wasDestroyed()) {
163             wasDestroyed = true;
164         } else {
165             size_t bytes = fBlocks[i].fBuffer->size() - fBlocks[i].fBytesFree;
166             bytesInUse += bytes;
167             SkASSERT(bytes || unusedBlockAllowed);
168         }
169     }
170 
171     if (!wasDestroyed) {
172         SkASSERT(bytesInUse == fBytesInUse);
173         if (unusedBlockAllowed) {
174             SkASSERT((fBytesInUse && !fBlocks.empty()) ||
175                      (!fBytesInUse && (fBlocks.size() < 2)));
176         } else {
177             SkASSERT((0 == fBytesInUse) == fBlocks.empty());
178         }
179     }
180 }
181 #endif
182 
align_up_pad(size_t x,size_t alignment)183 static inline size_t align_up_pad(size_t x, size_t alignment) {
184     return (alignment - x % alignment) % alignment;
185 }
186 
align_down(size_t x,uint32_t alignment)187 static inline size_t align_down(size_t x, uint32_t alignment) {
188     return (x / alignment) * alignment;
189 }
190 
makeSpace(size_t size,size_t alignment,sk_sp<const GrBuffer> * buffer,size_t * offset)191 void* GrBufferAllocPool::makeSpace(size_t size,
192                                    size_t alignment,
193                                    sk_sp<const GrBuffer>* buffer,
194                                    size_t* offset) {
195     VALIDATE();
196 
197     SkASSERT(buffer);
198     SkASSERT(offset);
199 
200     if (fBufferPtr) {
201         BufferBlock& back = fBlocks.back();
202         size_t usedBytes = back.fBuffer->size() - back.fBytesFree;
203         size_t pad = align_up_pad(usedBytes, alignment);
204         SkSafeMath safeMath;
205         size_t alignedSize = safeMath.add(pad, size);
206         if (!safeMath.ok()) {
207             return nullptr;
208         }
209         if (alignedSize <= back.fBytesFree) {
210             memset((void*)(reinterpret_cast<intptr_t>(fBufferPtr) + usedBytes), 0, pad);
211             usedBytes += pad;
212             *offset = usedBytes;
213             *buffer = back.fBuffer;
214             back.fBytesFree -= alignedSize;
215             fBytesInUse += alignedSize;
216             VALIDATE();
217             return (void*)(reinterpret_cast<intptr_t>(fBufferPtr) + usedBytes);
218         }
219     }
220 
221     // We could honor the space request using by a partial update of the current
222     // VB (if there is room). But we don't currently use draw calls to GL that
223     // allow the driver to know that previously issued draws won't read from
224     // the part of the buffer we update. Also, when this was written the GL
225     // buffer implementation was cheating on the actual buffer size by shrinking
226     // the buffer in updateData() if the amount of data passed was less than
227     // the full buffer size. This is old code and both concerns may be obsolete.
228 
229     if (!this->createBlock(size)) {
230         return nullptr;
231     }
232     SkASSERT(fBufferPtr);
233 
234     *offset = 0;
235     BufferBlock& back = fBlocks.back();
236     *buffer = back.fBuffer;
237     back.fBytesFree -= size;
238     fBytesInUse += size;
239     VALIDATE();
240     return fBufferPtr;
241 }
242 
makeSpaceAtLeast(size_t minSize,size_t fallbackSize,size_t alignment,sk_sp<const GrBuffer> * buffer,size_t * offset,size_t * actualSize)243 void* GrBufferAllocPool::makeSpaceAtLeast(size_t minSize,
244                                           size_t fallbackSize,
245                                           size_t alignment,
246                                           sk_sp<const GrBuffer>* buffer,
247                                           size_t* offset,
248                                           size_t* actualSize) {
249     VALIDATE();
250 
251     SkASSERT(buffer);
252     SkASSERT(offset);
253     SkASSERT(actualSize);
254 
255     size_t usedBytes = (fBlocks.empty()) ? 0 : fBlocks.back().fBuffer->size() -
256                                                fBlocks.back().fBytesFree;
257     size_t pad = align_up_pad(usedBytes, alignment);
258     if (!fBufferPtr || fBlocks.empty() || (minSize + pad) > fBlocks.back().fBytesFree) {
259         // We either don't have a block yet or the current block doesn't have enough free space.
260         // Create a new one.
261         if (!this->createBlock(fallbackSize)) {
262             return nullptr;
263         }
264         usedBytes = 0;
265         pad = 0;
266     }
267     SkASSERT(fBufferPtr);
268 
269     // Consume padding first, to make subsequent alignment math easier
270     memset(static_cast<char*>(fBufferPtr) + usedBytes, 0, pad);
271     usedBytes += pad;
272     fBlocks.back().fBytesFree -= pad;
273     fBytesInUse += pad;
274 
275     // Give caller all remaining space in this block (but aligned correctly)
276     size_t size = align_down(fBlocks.back().fBytesFree, alignment);
277     *offset = usedBytes;
278     *buffer = fBlocks.back().fBuffer;
279     *actualSize = size;
280     fBlocks.back().fBytesFree -= size;
281     fBytesInUse += size;
282     VALIDATE();
283     return static_cast<char*>(fBufferPtr) + usedBytes;
284 }
285 
putBack(size_t bytes)286 void GrBufferAllocPool::putBack(size_t bytes) {
287     VALIDATE();
288     if (!bytes) {
289         return;
290     }
291     SkASSERT(!fBlocks.empty());
292     BufferBlock& block = fBlocks.back();
293     // Caller shouldn't try to put back more than they've taken and all those bytes should fit into
294     // one block. All the uses of this call are sequential with a single makeSpaceAtLeast call. So
295     // we should not have a case where someone is putting back bytes that are greater than the
296     // current block.
297     // It is possible the caller returns all their allocated bytes thus the <= and not just <.
298     SkASSERT(bytes <= (block.fBuffer->size() - block.fBytesFree));
299     block.fBytesFree += bytes;
300     fBytesInUse -= bytes;
301 
302     // We don't allow blocks without any used bytes. So if we end up in that case after putting
303     // back the bytes then destroy the block. This scenario shouldn't occur often, but even if we
304     // end up allocating a new block immediately after destroying this one, the GPU and CPU buffers
305     // will usually be cached so the new block shouldn't be too expensive to make.
306     // TODO: This was true in older versions and uses of this class but is it still needed to
307     // have this restriction?
308     if (block.fBytesFree == block.fBuffer->size()) {
309         GrBuffer* buffer = block.fBuffer.get();
310         if (!buffer->isCpuBuffer() && static_cast<GrGpuBuffer*>(buffer)->isMapped()) {
311             UNMAP_BUFFER(block);
312         }
313         this->destroyBlock();
314     }
315 
316     VALIDATE();
317 }
318 
createBlock(size_t requestSize)319 bool GrBufferAllocPool::createBlock(size_t requestSize) {
320     size_t size = std::max(requestSize, kDefaultBufferSize);
321 
322     VALIDATE();
323 
324     BufferBlock& block = fBlocks.push_back();
325 
326     block.fBuffer = this->getBuffer(size);
327     if (!block.fBuffer) {
328         fBlocks.pop_back();
329         return false;
330     }
331 
332     block.fBytesFree = block.fBuffer->size();
333     if (fBufferPtr) {
334         SkASSERT(fBlocks.size() > 1);
335         BufferBlock& prev = fBlocks.fromBack(1);
336         GrBuffer* buffer = prev.fBuffer.get();
337         if (!buffer->isCpuBuffer()) {
338             if (static_cast<GrGpuBuffer*>(buffer)->isMapped()) {
339                 UNMAP_BUFFER(prev);
340             } else {
341                 this->flushCpuData(prev, prev.fBuffer->size() - prev.fBytesFree);
342             }
343         }
344         fBufferPtr = nullptr;
345     }
346 
347     SkASSERT(!fBufferPtr);
348 
349     // If the buffer is CPU-backed we "map" it because it is free to do so and saves a copy.
350     // Otherwise when buffer mapping is supported we map if the buffer size is greater than the
351     // threshold.
352     if (block.fBuffer->isCpuBuffer()) {
353         fBufferPtr = static_cast<GrCpuBuffer*>(block.fBuffer.get())->data();
354         SkASSERT(fBufferPtr);
355     } else {
356         if (GrCaps::kNone_MapFlags != fGpu->caps()->mapBufferFlags() &&
357             size > fGpu->caps()->bufferMapThreshold()) {
358             fBufferPtr = static_cast<GrGpuBuffer*>(block.fBuffer.get())->map();
359         }
360     }
361     if (!fBufferPtr) {
362         this->resetCpuData(block.fBytesFree);
363         fBufferPtr = fCpuStagingBuffer->data();
364     }
365 
366     VALIDATE(true);
367 
368     return true;
369 }
370 
destroyBlock()371 void GrBufferAllocPool::destroyBlock() {
372     SkASSERT(!fBlocks.empty());
373     SkASSERT(fBlocks.back().fBuffer->isCpuBuffer() ||
374              !static_cast<GrGpuBuffer*>(fBlocks.back().fBuffer.get())->isMapped());
375     fBlocks.pop_back();
376     fBufferPtr = nullptr;
377 }
378 
resetCpuData(size_t newSize)379 void GrBufferAllocPool::resetCpuData(size_t newSize) {
380     SkASSERT(newSize >= kDefaultBufferSize || !newSize);
381     if (!newSize) {
382         fCpuStagingBuffer.reset();
383         return;
384     }
385     if (fCpuStagingBuffer && newSize <= fCpuStagingBuffer->size()) {
386         return;
387     }
388     bool mustInitialize = fGpu->caps()->mustClearUploadedBufferData();
389     fCpuStagingBuffer = fCpuBufferCache ? fCpuBufferCache->makeBuffer(newSize, mustInitialize)
390                                         : GrCpuBuffer::Make(newSize);
391 }
392 
flushCpuData(const BufferBlock & block,size_t flushSize)393 void GrBufferAllocPool::flushCpuData(const BufferBlock& block, size_t flushSize) {
394     SkASSERT(block.fBuffer.get());
395     SkASSERT(!block.fBuffer.get()->isCpuBuffer());
396     GrGpuBuffer* buffer = static_cast<GrGpuBuffer*>(block.fBuffer.get());
397     SkASSERT(!buffer->isMapped());
398     SkASSERT(fCpuStagingBuffer && fCpuStagingBuffer->data() == fBufferPtr);
399     SkASSERT(flushSize <= buffer->size());
400     VALIDATE(true);
401 
402     if (GrCaps::kNone_MapFlags != fGpu->caps()->mapBufferFlags() &&
403         flushSize > fGpu->caps()->bufferMapThreshold()) {
404         void* data = buffer->map();
405         if (data) {
406             memcpy(data, fBufferPtr, flushSize);
407             UNMAP_BUFFER(block);
408             return;
409         }
410     }
411     buffer->updateData(fBufferPtr, /*offset=*/0, flushSize, /*preserve=*/false);
412     VALIDATE(true);
413 }
414 
getBuffer(size_t size)415 sk_sp<GrBuffer> GrBufferAllocPool::getBuffer(size_t size) {
416     const GrCaps& caps = *fGpu->caps();
417     auto resourceProvider = fGpu->getContext()->priv().resourceProvider();
418     if (caps.preferClientSideDynamicBuffers() ||
419         (fBufferType == GrGpuBufferType::kDrawIndirect && caps.useClientSideIndirectBuffers())) {
420         // Create a CPU buffer.
421         bool mustInitialize = caps.mustClearUploadedBufferData();
422         return fCpuBufferCache ? fCpuBufferCache->makeBuffer(size, mustInitialize)
423                                : GrCpuBuffer::Make(size);
424     }
425     return resourceProvider->createBuffer(size,
426                                           fBufferType,
427                                           kDynamic_GrAccessPattern,
428                                           GrResourceProvider::ZeroInit::kNo);
429 }
430 
431 ////////////////////////////////////////////////////////////////////////////////
432 
GrVertexBufferAllocPool(GrGpu * gpu,sk_sp<CpuBufferCache> cpuBufferCache)433 GrVertexBufferAllocPool::GrVertexBufferAllocPool(GrGpu* gpu, sk_sp<CpuBufferCache> cpuBufferCache)
434         : GrBufferAllocPool(gpu, GrGpuBufferType::kVertex, std::move(cpuBufferCache)) {}
435 
makeSpace(size_t vertexSize,int vertexCount,sk_sp<const GrBuffer> * buffer,int * startVertex)436 void* GrVertexBufferAllocPool::makeSpace(size_t vertexSize,
437                                          int vertexCount,
438                                          sk_sp<const GrBuffer>* buffer,
439                                          int* startVertex) {
440     SkASSERT(vertexCount >= 0);
441     SkASSERT(buffer);
442     SkASSERT(startVertex);
443 
444     size_t offset SK_INIT_TO_AVOID_WARNING;
445     void* ptr = INHERITED::makeSpace(SkSafeMath::Mul(vertexSize, vertexCount),
446                                      vertexSize,
447                                      buffer,
448                                      &offset);
449 
450     SkASSERT(0 == offset % vertexSize);
451     *startVertex = static_cast<int>(offset / vertexSize);
452     return ptr;
453 }
454 
makeSpaceAtLeast(size_t vertexSize,int minVertexCount,int fallbackVertexCount,sk_sp<const GrBuffer> * buffer,int * startVertex,int * actualVertexCount)455 void* GrVertexBufferAllocPool::makeSpaceAtLeast(size_t vertexSize, int minVertexCount,
456                                                 int fallbackVertexCount,
457                                                 sk_sp<const GrBuffer>* buffer, int* startVertex,
458                                                 int* actualVertexCount) {
459     SkASSERT(minVertexCount >= 0);
460     SkASSERT(fallbackVertexCount >= minVertexCount);
461     SkASSERT(buffer);
462     SkASSERT(startVertex);
463     SkASSERT(actualVertexCount);
464 
465     size_t offset SK_INIT_TO_AVOID_WARNING;
466     size_t actualSize SK_INIT_TO_AVOID_WARNING;
467     void* ptr = INHERITED::makeSpaceAtLeast(SkSafeMath::Mul(vertexSize, minVertexCount),
468                                             SkSafeMath::Mul(vertexSize, fallbackVertexCount),
469                                             vertexSize,
470                                             buffer,
471                                             &offset,
472                                             &actualSize);
473 
474     SkASSERT(0 == offset % vertexSize);
475     *startVertex = static_cast<int>(offset / vertexSize);
476 
477     SkASSERT(0 == actualSize % vertexSize);
478     SkASSERT(actualSize >= vertexSize * minVertexCount);
479     *actualVertexCount = static_cast<int>(actualSize / vertexSize);
480 
481     return ptr;
482 }
483 
484 ////////////////////////////////////////////////////////////////////////////////
485 
GrIndexBufferAllocPool(GrGpu * gpu,sk_sp<CpuBufferCache> cpuBufferCache)486 GrIndexBufferAllocPool::GrIndexBufferAllocPool(GrGpu* gpu, sk_sp<CpuBufferCache> cpuBufferCache)
487         : GrBufferAllocPool(gpu, GrGpuBufferType::kIndex, std::move(cpuBufferCache)) {}
488 
makeSpace(int indexCount,sk_sp<const GrBuffer> * buffer,int * startIndex)489 void* GrIndexBufferAllocPool::makeSpace(int indexCount, sk_sp<const GrBuffer>* buffer,
490                                         int* startIndex) {
491     SkASSERT(indexCount >= 0);
492     SkASSERT(buffer);
493     SkASSERT(startIndex);
494 
495     size_t offset SK_INIT_TO_AVOID_WARNING;
496     void* ptr = INHERITED::makeSpace(SkSafeMath::Mul(indexCount, sizeof(uint16_t)),
497                                      sizeof(uint16_t),
498                                      buffer,
499                                      &offset);
500 
501     SkASSERT(0 == offset % sizeof(uint16_t));
502     *startIndex = static_cast<int>(offset / sizeof(uint16_t));
503     return ptr;
504 }
505 
makeSpaceAtLeast(int minIndexCount,int fallbackIndexCount,sk_sp<const GrBuffer> * buffer,int * startIndex,int * actualIndexCount)506 void* GrIndexBufferAllocPool::makeSpaceAtLeast(int minIndexCount, int fallbackIndexCount,
507                                                sk_sp<const GrBuffer>* buffer, int* startIndex,
508                                                int* actualIndexCount) {
509     SkASSERT(minIndexCount >= 0);
510     SkASSERT(fallbackIndexCount >= minIndexCount);
511     SkASSERT(buffer);
512     SkASSERT(startIndex);
513     SkASSERT(actualIndexCount);
514 
515     size_t offset SK_INIT_TO_AVOID_WARNING;
516     size_t actualSize SK_INIT_TO_AVOID_WARNING;
517     void* ptr = INHERITED::makeSpaceAtLeast(SkSafeMath::Mul(minIndexCount, sizeof(uint16_t)),
518                                             SkSafeMath::Mul(fallbackIndexCount, sizeof(uint16_t)),
519                                             sizeof(uint16_t),
520                                             buffer,
521                                             &offset,
522                                             &actualSize);
523 
524     SkASSERT(0 == offset % sizeof(uint16_t));
525     *startIndex = static_cast<int>(offset / sizeof(uint16_t));
526 
527     SkASSERT(0 == actualSize % sizeof(uint16_t));
528     SkASSERT(actualSize >= minIndexCount * sizeof(uint16_t));
529     *actualIndexCount = static_cast<int>(actualSize / sizeof(uint16_t));
530     return ptr;
531 }
532