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/*
* 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 "SkRWBuffer.h"
#include "SkStream.h"
// Force small chunks to be a page's worth
static const size_t kMinAllocSize = 4096;
struct SkBufferBlock {
SkBufferBlock* fNext;
size_t fUsed;
size_t fCapacity;
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);
SkBufferBlock* block = (SkBufferBlock*)sk_malloc_throw(sizeof(SkBufferBlock) + capacity);
block->fNext = nullptr;
block->fUsed = 0;
block->fCapacity = capacity;
return block;
}
// Return number of bytes actually appended
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;
}
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;
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;
SkBufferHead* head = (SkBufferHead*)sk_malloc_throw(size);
head->fRefCnt = 1;
head->fBlock.fNext = nullptr;
head->fBlock.fUsed = 0;
head->fBlock.fCapacity = capacity;
return head;
}
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, 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
}
};
SkROBuffer::SkROBuffer(const SkBufferHead* head, size_t used) : fHead(head), fUsed(used) {
if (head) {
fHead->ref();
SkASSERT(used > 0);
head->validate(used);
} else {
SkASSERT(0 == used);
}
}
SkROBuffer::~SkROBuffer() {
if (fHead) {
fHead->validate(fUsed);
fHead->unref();
}
}
SkROBuffer::Iter::Iter(const SkROBuffer* buffer) {
this->reset(buffer);
}
void SkROBuffer::Iter::reset(const SkROBuffer* buffer) {
if (buffer) {
fBlock = &buffer->fHead->fBlock;
fRemaining = buffer->fUsed;
} 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->fUsed, fRemaining);
}
bool SkROBuffer::Iter::next() {
if (fRemaining) {
fRemaining -= this->size();
fBlock = fBlock->fNext;
}
return fRemaining != 0;
}
SkRWBuffer::SkRWBuffer(size_t initialCapacity) : fHead(nullptr), fTail(nullptr), fTotalUsed(0) {}
SkRWBuffer::~SkRWBuffer() {
this->validate();
if (fHead) {
fHead->unref();
}
}
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();
}
void* SkRWBuffer::append(size_t length) {
this->validate();
if (0 == length) {
return nullptr;
}
fTotalUsed += length;
if (nullptr == fHead) {
fHead = SkBufferHead::Alloc(length);
fTail = &fHead->fBlock;
} else if (fTail->avail() < length) {
SkBufferBlock* block = SkBufferBlock::Alloc(length);
fTail->fNext = block;
fTail = block;
}
fTail->fUsed += length;
this->validate();
return (char*)fTail->availData() - length;
}
#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); }
///////////////////////////////////////////////////////////////////////////////////////////////////
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);
}
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