| /* |
| * Copyright 2015 Google Inc. |
| * |
| * Use of this source code is governed by a BSD-style license that can be |
| * found in the LICENSE file. |
| */ |
| |
| #include "SkAtomics.h" |
| #include "SkRWBuffer.h" |
| #include "SkStream.h" |
| |
| // Force small chunks to be a page's worth |
| static const size_t kMinAllocSize = 4096; |
| |
| struct SkBufferBlock { |
| SkBufferBlock* fNext; // updated by the writer |
| size_t fUsed; // updated by the writer |
| const size_t fCapacity; |
| |
| SkBufferBlock(size_t capacity) : fNext(nullptr), fUsed(0), fCapacity(capacity) {} |
| |
| const void* startData() const { return this + 1; } |
| |
| size_t avail() const { return fCapacity - fUsed; } |
| void* availData() { return (char*)this->startData() + fUsed; } |
| |
| static SkBufferBlock* Alloc(size_t length) { |
| size_t capacity = LengthToCapacity(length); |
| void* buffer = sk_malloc_throw(sizeof(SkBufferBlock) + capacity); |
| return new (buffer) SkBufferBlock(capacity); |
| } |
| |
| // Return number of bytes actually appended. Important that we always completely this block |
| // before spilling into the next, since the reader uses fCapacity to know how many it can read. |
| // |
| size_t append(const void* src, size_t length) { |
| this->validate(); |
| size_t amount = SkTMin(this->avail(), length); |
| memcpy(this->availData(), src, amount); |
| fUsed += amount; |
| this->validate(); |
| return amount; |
| } |
| |
| // Do not call in the reader thread, since the writer may be updating fUsed. |
| // (The assertion is still true, but TSAN still may complain about its raciness.) |
| void validate() const { |
| #ifdef SK_DEBUG |
| SkASSERT(fCapacity > 0); |
| SkASSERT(fUsed <= fCapacity); |
| #endif |
| } |
| |
| private: |
| static size_t LengthToCapacity(size_t length) { |
| const size_t minSize = kMinAllocSize - sizeof(SkBufferBlock); |
| return SkTMax(length, minSize); |
| } |
| }; |
| |
| struct SkBufferHead { |
| mutable int32_t fRefCnt; |
| SkBufferBlock fBlock; |
| |
| SkBufferHead(size_t capacity) : fRefCnt(1), fBlock(capacity) {} |
| |
| static size_t LengthToCapacity(size_t length) { |
| const size_t minSize = kMinAllocSize - sizeof(SkBufferHead); |
| return SkTMax(length, minSize); |
| } |
| |
| static SkBufferHead* Alloc(size_t length) { |
| size_t capacity = LengthToCapacity(length); |
| size_t size = sizeof(SkBufferHead) + capacity; |
| void* buffer = sk_malloc_throw(size); |
| return new (buffer) SkBufferHead(capacity); |
| } |
| |
| void ref() const { |
| SkASSERT(fRefCnt > 0); |
| sk_atomic_inc(&fRefCnt); |
| } |
| |
| void unref() const { |
| SkASSERT(fRefCnt > 0); |
| // A release here acts in place of all releases we "should" have been doing in ref(). |
| if (1 == sk_atomic_fetch_add(&fRefCnt, -1, sk_memory_order_acq_rel)) { |
| // Like unique(), the acquire is only needed on success. |
| SkBufferBlock* block = fBlock.fNext; |
| sk_free((void*)this); |
| while (block) { |
| SkBufferBlock* next = block->fNext; |
| sk_free(block); |
| block = next; |
| } |
| } |
| } |
| |
| void validate(size_t minUsed, const SkBufferBlock* tail = nullptr) const { |
| #ifdef SK_DEBUG |
| SkASSERT(fRefCnt > 0); |
| size_t totalUsed = 0; |
| const SkBufferBlock* block = &fBlock; |
| const SkBufferBlock* lastBlock = block; |
| while (block) { |
| block->validate(); |
| totalUsed += block->fUsed; |
| lastBlock = block; |
| block = block->fNext; |
| } |
| SkASSERT(minUsed <= totalUsed); |
| if (tail) { |
| SkASSERT(tail == lastBlock); |
| } |
| #endif |
| } |
| }; |
| |
| /////////////////////////////////////////////////////////////////////////////////////////////////// |
| // The reader can only access block.fCapacity (which never changes), and cannot access |
| // block.fUsed, which may be updated by the writer. |
| // |
| SkROBuffer::SkROBuffer(const SkBufferHead* head, size_t available, const SkBufferBlock* tail) |
| : fHead(head), fAvailable(available), fTail(tail) |
| { |
| if (head) { |
| fHead->ref(); |
| SkASSERT(available > 0); |
| head->validate(available, tail); |
| } else { |
| SkASSERT(0 == available); |
| SkASSERT(!tail); |
| } |
| } |
| |
| SkROBuffer::~SkROBuffer() { |
| if (fHead) { |
| fHead->unref(); |
| } |
| } |
| |
| SkROBuffer::Iter::Iter(const SkROBuffer* buffer) { |
| this->reset(buffer); |
| } |
| |
| void SkROBuffer::Iter::reset(const SkROBuffer* buffer) { |
| fBuffer = buffer; |
| if (buffer && buffer->fHead) { |
| fBlock = &buffer->fHead->fBlock; |
| fRemaining = buffer->fAvailable; |
| } else { |
| fBlock = nullptr; |
| fRemaining = 0; |
| } |
| } |
| |
| const void* SkROBuffer::Iter::data() const { |
| return fRemaining ? fBlock->startData() : nullptr; |
| } |
| |
| size_t SkROBuffer::Iter::size() const { |
| if (!fBlock) { |
| return 0; |
| } |
| return SkTMin(fBlock->fCapacity, fRemaining); |
| } |
| |
| bool SkROBuffer::Iter::next() { |
| if (fRemaining) { |
| fRemaining -= this->size(); |
| if (fBuffer->fTail == fBlock) { |
| // There are more blocks, but fBuffer does not know about them. |
| SkASSERT(0 == fRemaining); |
| fBlock = nullptr; |
| } else { |
| fBlock = fBlock->fNext; |
| } |
| } |
| return fRemaining != 0; |
| } |
| |
| /////////////////////////////////////////////////////////////////////////////////////////////////// |
| |
| SkRWBuffer::SkRWBuffer(size_t initialCapacity) : fHead(nullptr), fTail(nullptr), fTotalUsed(0) { |
| if (initialCapacity) { |
| fHead = SkBufferHead::Alloc(initialCapacity); |
| fTail = &fHead->fBlock; |
| } |
| } |
| |
| SkRWBuffer::~SkRWBuffer() { |
| this->validate(); |
| if (fHead) { |
| fHead->unref(); |
| } |
| } |
| |
| // It is important that we always completely fill the current block before spilling over to the |
| // next, since our reader will be using fCapacity (min'd against its total available) to know how |
| // many bytes to read from a given block. |
| // |
| void SkRWBuffer::append(const void* src, size_t length) { |
| this->validate(); |
| if (0 == length) { |
| return; |
| } |
| |
| fTotalUsed += length; |
| |
| if (nullptr == fHead) { |
| fHead = SkBufferHead::Alloc(length); |
| fTail = &fHead->fBlock; |
| } |
| |
| size_t written = fTail->append(src, length); |
| SkASSERT(written <= length); |
| src = (const char*)src + written; |
| length -= written; |
| |
| if (length) { |
| SkBufferBlock* block = SkBufferBlock::Alloc(length); |
| fTail->fNext = block; |
| fTail = block; |
| written = fTail->append(src, length); |
| SkASSERT(written == length); |
| } |
| this->validate(); |
| } |
| |
| #ifdef SK_DEBUG |
| void SkRWBuffer::validate() const { |
| if (fHead) { |
| fHead->validate(fTotalUsed, fTail); |
| } else { |
| SkASSERT(nullptr == fTail); |
| SkASSERT(0 == fTotalUsed); |
| } |
| } |
| #endif |
| |
| SkROBuffer* SkRWBuffer::newRBufferSnapshot() const { |
| return new SkROBuffer(fHead, fTotalUsed, fTail); |
| } |
| |
| /////////////////////////////////////////////////////////////////////////////////////////////////// |
| |
| class SkROBufferStreamAsset : public SkStreamAsset { |
| void validate() const { |
| #ifdef SK_DEBUG |
| SkASSERT(fGlobalOffset <= fBuffer->size()); |
| SkASSERT(fLocalOffset <= fIter.size()); |
| SkASSERT(fLocalOffset <= fGlobalOffset); |
| #endif |
| } |
| |
| #ifdef SK_DEBUG |
| class AutoValidate { |
| SkROBufferStreamAsset* fStream; |
| public: |
| AutoValidate(SkROBufferStreamAsset* stream) : fStream(stream) { stream->validate(); } |
| ~AutoValidate() { fStream->validate(); } |
| }; |
| #define AUTO_VALIDATE AutoValidate av(this); |
| #else |
| #define AUTO_VALIDATE |
| #endif |
| |
| public: |
| SkROBufferStreamAsset(const SkROBuffer* buffer) : fBuffer(SkRef(buffer)), fIter(buffer) { |
| fGlobalOffset = fLocalOffset = 0; |
| } |
| |
| virtual ~SkROBufferStreamAsset() { fBuffer->unref(); } |
| |
| size_t getLength() const override { return fBuffer->size(); } |
| |
| bool rewind() override { |
| AUTO_VALIDATE |
| fIter.reset(fBuffer); |
| fGlobalOffset = fLocalOffset = 0; |
| return true; |
| } |
| |
| size_t read(void* dst, size_t request) override { |
| AUTO_VALIDATE |
| size_t bytesRead = 0; |
| for (;;) { |
| size_t size = fIter.size(); |
| SkASSERT(fLocalOffset <= size); |
| size_t avail = SkTMin(size - fLocalOffset, request - bytesRead); |
| if (dst) { |
| memcpy(dst, (const char*)fIter.data() + fLocalOffset, avail); |
| dst = (char*)dst + avail; |
| } |
| bytesRead += avail; |
| fLocalOffset += avail; |
| SkASSERT(bytesRead <= request); |
| if (bytesRead == request) { |
| break; |
| } |
| // If we get here, we've exhausted the current iter |
| SkASSERT(fLocalOffset == size); |
| fLocalOffset = 0; |
| if (!fIter.next()) { |
| break; // ran out of data |
| } |
| } |
| fGlobalOffset += bytesRead; |
| SkASSERT(fGlobalOffset <= fBuffer->size()); |
| return bytesRead; |
| } |
| |
| bool isAtEnd() const override { |
| return fBuffer->size() == fGlobalOffset; |
| } |
| |
| SkStreamAsset* duplicate() const override { return new SkROBufferStreamAsset(fBuffer); } |
| |
| size_t getPosition() const override { |
| return fGlobalOffset; |
| } |
| |
| bool seek(size_t position) override { |
| AUTO_VALIDATE |
| if (position < fGlobalOffset) { |
| this->rewind(); |
| } |
| (void)this->skip(position - fGlobalOffset); |
| return true; |
| } |
| |
| bool move(long offset) override{ |
| AUTO_VALIDATE |
| offset += fGlobalOffset; |
| if (offset <= 0) { |
| this->rewind(); |
| } else { |
| (void)this->seek(SkToSizeT(offset)); |
| } |
| return true; |
| } |
| |
| SkStreamAsset* fork() const override { |
| SkStreamAsset* clone = this->duplicate(); |
| clone->seek(this->getPosition()); |
| return clone; |
| } |
| |
| |
| private: |
| const SkROBuffer* fBuffer; |
| SkROBuffer::Iter fIter; |
| size_t fLocalOffset; |
| size_t fGlobalOffset; |
| }; |
| |
| SkStreamAsset* SkRWBuffer::newStreamSnapshot() const { |
| SkAutoTUnref<SkROBuffer> buffer(this->newRBufferSnapshot()); |
| return new SkROBufferStreamAsset(buffer); |
| } |