The Tor Browser: comparison gfx/skia/trunk/src/utils/SkFrontBufferedStream.cpp

--1:000000000000
+:367a703e654c
+/*
+* Copyright 2013 Google Inc.
+*
+* Use of this source code is governed by a BSD-style license that can be
+* found in the LICENSE file.
+*/
+#include "SkFrontBufferedStream.h"
+#include "SkStream.h"
+#include "SkTemplates.h"
+class FrontBufferedStream : public SkStreamRewindable {
+public:
+// Called by Create.
+FrontBufferedStream(SkStream*, size_t bufferSize);
+virtual size_t read(void* buffer, size_t size) SK_OVERRIDE;
+virtual bool isAtEnd() const SK_OVERRIDE;
+virtual bool rewind() SK_OVERRIDE;
+virtual bool hasPosition() const SK_OVERRIDE { return true; }
+virtual size_t getPosition() const SK_OVERRIDE { return fOffset; }
+virtual bool hasLength() const SK_OVERRIDE { return fHasLength; }
+virtual size_t getLength() const SK_OVERRIDE { return fLength; }
+virtual SkStreamRewindable* duplicate() const SK_OVERRIDE { return NULL; }
+private:
+SkAutoTUnref<SkStream>  fStream;
+const bool              fHasLength;
+const size_t            fLength;
+// Current offset into the stream. Always >= 0.
+size_t                  fOffset;
+// Amount that has been buffered by calls to read. Will always be less than
+// fBufferSize.
+size_t                  fBufferedSoFar;
+// Total size of the buffer.
+const size_t            fBufferSize;
+// FIXME: SkAutoTMalloc throws on failure. Instead, Create should return a
+// NULL stream.
+SkAutoTMalloc<char>     fBuffer;
+// Read up to size bytes from already buffered data, and copy to
+// dst, if non-NULL. Updates fOffset. Assumes that fOffset is less
+// than fBufferedSoFar.
+size_t readFromBuffer(char* dst, size_t size);
+// Buffer up to size bytes from the stream, and copy to dst if non-
+// NULL. Updates fOffset and fBufferedSoFar. Assumes that fOffset is
+// less than fBufferedSoFar, and size is greater than 0.
+size_t bufferAndWriteTo(char* dst, size_t size);
+// Read up to size bytes directly from the stream and into dst if non-
+// NULL. Updates fOffset. Assumes fOffset is at or beyond the buffered
+// data, and size is greater than 0.
+size_t readDirectlyFromStream(char* dst, size_t size);
+typedef SkStream INHERITED;
+};
+SkStreamRewindable* SkFrontBufferedStream::Create(SkStream* stream, size_t bufferSize) {
+if (NULL == stream) {
+return NULL;
+}
+return SkNEW_ARGS(FrontBufferedStream, (stream, bufferSize));
+}
+FrontBufferedStream::FrontBufferedStream(SkStream* stream, size_t bufferSize)
+: fStream(SkRef(stream))
+, fHasLength(stream->hasPosition() && stream->hasLength())
+, fLength(stream->getLength() - stream->getPosition())
+, fOffset(0)
+, fBufferedSoFar(0)
+, fBufferSize(bufferSize)
+, fBuffer(bufferSize) {}
+bool FrontBufferedStream::isAtEnd() const {
+if (fOffset < fBufferedSoFar) {
+// Even if the underlying stream is at the end, this stream has been
+// rewound after buffering, so it is not at the end.
+return false;
+}
+return fStream->isAtEnd();
+}
+bool FrontBufferedStream::rewind() {
+// Only allow a rewind if we have not exceeded the buffer.
+if (fOffset <= fBufferSize) {
+fOffset = 0;
+return true;
+}
+return false;
+}
+size_t FrontBufferedStream::readFromBuffer(char* dst, size_t size) {
+SkASSERT(fOffset < fBufferedSoFar);
+// Some data has already been copied to fBuffer. Read up to the
+// lesser of the size requested and the remainder of the buffered
+// data.
+const size_t bytesToCopy = SkTMin(size, fBufferedSoFar - fOffset);
+if (dst != NULL) {
+memcpy(dst, fBuffer + fOffset, bytesToCopy);
+}
+// Update fOffset to the new position. It is guaranteed to be
+// within the buffered data.
+fOffset += bytesToCopy;
+SkASSERT(fOffset <= fBufferedSoFar);
+return bytesToCopy;
+}
+size_t FrontBufferedStream::bufferAndWriteTo(char* dst, size_t size) {
+SkASSERT(size > 0);
+SkASSERT(fOffset >= fBufferedSoFar);
+// Data needs to be buffered. Buffer up to the lesser of the size requested
+// and the remainder of the max buffer size.
+const size_t bytesToBuffer = SkTMin(size, fBufferSize - fBufferedSoFar);
+char* buffer = fBuffer + fOffset;
+const size_t buffered = fStream->read(buffer, bytesToBuffer);
+fBufferedSoFar += buffered;
+fOffset = fBufferedSoFar;
+SkASSERT(fBufferedSoFar <= fBufferSize);
+// Copy the buffer to the destination buffer and update the amount read.
+if (dst != NULL) {
+memcpy(dst, buffer, buffered);
+}
+return buffered;
+}
+size_t FrontBufferedStream::readDirectlyFromStream(char* dst, size_t size) {
+SkASSERT(size > 0);
+// If we get here, we have buffered all that can be buffered.
+SkASSERT(fBufferSize == fBufferedSoFar && fOffset >= fBufferSize);
+const size_t bytesReadDirectly = fStream->read(dst, size);
+fOffset += bytesReadDirectly;
+// If we have read past the end of the buffer, rewinding is no longer
+// supported, so we can go ahead and free the memory.
+if (bytesReadDirectly > 0) {
+fBuffer.reset(0);
+}
+return bytesReadDirectly;
+}
+size_t FrontBufferedStream::read(void* voidDst, size_t size) {
+// Cast voidDst to a char* for easy addition.
+char* dst = reinterpret_cast<char*>(voidDst);
+SkDEBUGCODE(const size_t totalSize = size;)
+const size_t start = fOffset;
+// First, read any data that was previously buffered.
+if (fOffset < fBufferedSoFar) {
+const size_t bytesCopied = this->readFromBuffer(dst, size);
+// Update the remaining number of bytes needed to read
+// and the destination buffer.
+size -= bytesCopied;
+SkASSERT(size + (fOffset - start) == totalSize);
+if (dst != NULL) {
+dst += bytesCopied;
+}
+}
+// Buffer any more data that should be buffered, and copy it to the
+// destination.
+if (size > 0 && fBufferedSoFar < fBufferSize) {
+const size_t buffered = this->bufferAndWriteTo(dst, size);
+// Update the remaining number of bytes needed to read
+// and the destination buffer.
+size -= buffered;
+SkASSERT(size + (fOffset - start) == totalSize);
+if (dst != NULL) {
+dst += buffered;
+}
+}
+if (size > 0 && !fStream->isAtEnd()) {
+SkDEBUGCODE(const size_t bytesReadDirectly =) this->readDirectlyFromStream(dst, size);
+SkDEBUGCODE(size -= bytesReadDirectly;)
+SkASSERT(size + (fOffset - start) == totalSize);
+}
+return fOffset - start;
+}

The Tor Browser / file comparison

comparison: gfx/skia/trunk/src/utils/SkFrontBufferedStream.cpp

gfx/skia/trunk/src/utils/SkFrontBufferedStream.cpp