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| 1 /* |
| 2 * Copyright 2013 Google Inc. |
| 3 * |
| 4 * Use of this source code is governed by a BSD-style license that can be |
| 5 * found in the LICENSE file. |
| 6 */ |
| 7 |
| 8 #include "SkStream.h" |
| 9 #include "SkTemplates.h" |
| 10 |
| 11 /** |
| 12 * Specialized stream that only buffers the first X bytes of a stream, |
| 13 * where X is passed in by the user. Note that unlike some buffered |
| 14 * stream APIs, once more than those bytes are read, no more buffering |
| 15 * is done. This stream is designed for a use case where the caller |
| 16 * knows that rewind will only be called from within X bytes (inclusive), |
| 17 * and the wrapped stream is not necessarily able to rewind at all. |
| 18 */ |
| 19 class SkFrontBufferedStream : public SkStreamRewindable { |
| 20 public: |
| 21 /** |
| 22 * Creates a new stream that wraps and buffers SkStream. |
| 23 * @param stream SkStream to buffer. If NULL, NULL is returned. After |
| 24 * this call, unref stream and do not refer to it. |
| 25 * SkFrontBufferedStream is expected to be its only owner. |
| 26 * @param bufferSize Exact size of the buffer to be used. |
| 27 * @return An SkStream that can buffer up to bufferSize. |
| 28 */ |
| 29 static SkStreamRewindable* Create(SkStream* stream, size_t bufferSize); |
| 30 |
| 31 virtual size_t read(void* buffer, size_t size) SK_OVERRIDE; |
| 32 |
| 33 virtual bool isAtEnd() const SK_OVERRIDE; |
| 34 |
| 35 virtual bool rewind() SK_OVERRIDE; |
| 36 |
| 37 virtual bool hasPosition() const SK_OVERRIDE { return true; } |
| 38 |
| 39 virtual size_t getPosition() const SK_OVERRIDE { return fOffset; } |
| 40 |
| 41 virtual bool hasLength() const SK_OVERRIDE; |
| 42 |
| 43 virtual size_t getLength() const SK_OVERRIDE; |
| 44 |
| 45 virtual SkStreamRewindable* duplicate() const SK_OVERRIDE { return NULL; } |
| 46 |
| 47 private: |
| 48 SkAutoTUnref<SkStream> fStream; |
| 49 // Current offset into the stream. Always >= 0. |
| 50 size_t fOffset; |
| 51 // Amount that has been buffered by calls to read. Will always be less than |
| 52 // fBufferSize. |
| 53 size_t fBufferedSoFar; |
| 54 // Total size of the buffer. |
| 55 const size_t fBufferSize; |
| 56 SkAutoTMalloc<char> fBuffer; |
| 57 |
| 58 // Private. Use Create. |
| 59 SkFrontBufferedStream(SkStream*, size_t bufferSize); |
| 60 |
| 61 // Read up to size bytes from already buffered data, and copy to |
| 62 // dst, if non-NULL. Updates fOffset. Assumes that fOffset is less |
| 63 // than fBufferedSoFar. |
| 64 size_t readFromBuffer(char* dst, size_t size); |
| 65 |
| 66 // Buffer up to size bytes from the stream, and copy to dst if non- |
| 67 // NULL. Updates fOffset and fBufferedSoFar. Assumes that fOffset is |
| 68 // less than fBufferedSoFar, and size is greater than 0. |
| 69 size_t bufferAndWriteTo(char* dst, size_t size); |
| 70 |
| 71 // Read up to size bytes directly from the stream and into dst if non- |
| 72 // NULL. Updates fOffset. Assumes fOffset is at or beyond the buffered |
| 73 // data, and size is greater than 0. |
| 74 size_t readDirectlyFromStream(char* dst, size_t size); |
| 75 |
| 76 typedef SkStream INHERITED; |
| 77 }; |
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