The Tor Browser: gfx/skia/trunk/src/utils/SkFrontBufferedStream.cpp@b8a032363ba2 (annotated)

gfx/skia/trunk/src/utils/SkFrontBufferedStream.cpp@b8a032363ba2 (annotated)

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

Thu, 22 Jan 2015 13:21:57 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Thu, 22 Jan 2015 13:21:57 +0100
branch: TOR_BUG_9701
changeset 15: b8a032363ba2
permissions: -rw-r--r--

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

 /*
  * 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;
 }

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gfx/skia/trunk/src/utils/SkFrontBufferedStream.cpp@b8a032363ba2 (annotated)

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