| /* |
| * 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 "SkStream.h" |
| #include "SkTemplates.h" |
| |
| /** |
| * Specialized stream that only buffers the first X bytes of a stream, |
| * where X is passed in by the user. Note that unlike some buffered |
| * stream APIs, once more than those bytes are read, no more buffering |
| * is done. This stream is designed for a use case where the caller |
| * knows that rewind will only be called from within X bytes (inclusive), |
| * and the wrapped stream is not necessarily able to rewind at all. |
| */ |
| class SkFrontBufferedStream : public SkStreamRewindable { |
| public: |
| /** |
| * Creates a new stream that wraps and buffers SkStream. |
| * @param stream SkStream to buffer. If NULL, NULL is returned. After |
| * this call, unref stream and do not refer to it. |
| * SkFrontBufferedStream is expected to be its only owner. |
| * @param bufferSize Exact size of the buffer to be used. |
| * @return An SkStream that can buffer up to bufferSize. |
| */ |
| static SkStreamRewindable* Create(SkStream* stream, 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; |
| |
| virtual size_t getLength() const SK_OVERRIDE; |
| |
| virtual SkStreamRewindable* duplicate() const SK_OVERRIDE { return NULL; } |
| |
| private: |
| SkAutoTUnref<SkStream> fStream; |
| // 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; |
| SkAutoTMalloc<char> fBuffer; |
| |
| // Private. Use Create. |
| SkFrontBufferedStream(SkStream*, size_t bufferSize); |
| |
| // 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; |
| }; |