83fd2c7c43
This is used by Android to buffer an input stream which may not otherwise be able to rewind. Add a test for the new class. R=bungeman@google.com, mtklein@google.com, reed@google.com Review URL: https://codereview.chromium.org/23717055 git-svn-id: http://skia.googlecode.com/svn/trunk@11488 2bbb7eff-a529-9590-31e7-b0007b416f81
78 lines
2.8 KiB
C++
78 lines
2.8 KiB
C++
/*
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* Copyright 2013 Google Inc.
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*
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* Use of this source code is governed by a BSD-style license that can be
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* found in the LICENSE file.
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*/
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#include "SkStream.h"
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#include "SkTemplates.h"
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/**
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* Specialized stream that only buffers the first X bytes of a stream,
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* where X is passed in by the user. Note that unlike some buffered
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* stream APIs, once more than those bytes are read, no more buffering
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* is done. This stream is designed for a use case where the caller
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* knows that rewind will only be called from within X bytes (inclusive),
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* and the wrapped stream is not necessarily able to rewind at all.
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*/
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class SkFrontBufferedStream : public SkStreamRewindable {
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public:
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/**
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* Creates a new stream that wraps and buffers SkStream.
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* @param stream SkStream to buffer. If NULL, NULL is returned. After
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* this call, unref stream and do not refer to it.
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* SkFrontBufferedStream is expected to be its only owner.
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* @param bufferSize Exact size of the buffer to be used.
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* @return An SkStream that can buffer up to bufferSize.
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*/
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static SkStreamRewindable* Create(SkStream* stream, size_t bufferSize);
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virtual size_t read(void* buffer, size_t size) SK_OVERRIDE;
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virtual bool isAtEnd() const SK_OVERRIDE;
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virtual bool rewind() SK_OVERRIDE;
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virtual bool hasPosition() const SK_OVERRIDE { return true; }
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virtual size_t getPosition() const SK_OVERRIDE { return fOffset; }
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virtual bool hasLength() const SK_OVERRIDE;
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virtual size_t getLength() const SK_OVERRIDE;
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virtual SkStreamRewindable* duplicate() const SK_OVERRIDE { return NULL; }
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private:
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SkAutoTUnref<SkStream> fStream;
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// Current offset into the stream. Always >= 0.
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size_t fOffset;
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// Amount that has been buffered by calls to read. Will always be less than
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// fBufferSize.
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size_t fBufferedSoFar;
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// Total size of the buffer.
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const size_t fBufferSize;
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SkAutoTMalloc<char> fBuffer;
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// Private. Use Create.
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SkFrontBufferedStream(SkStream*, size_t bufferSize);
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// Read up to size bytes from already buffered data, and copy to
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// dst, if non-NULL. Updates fOffset. Assumes that fOffset is less
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// than fBufferedSoFar.
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size_t readFromBuffer(char* dst, size_t size);
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// Buffer up to size bytes from the stream, and copy to dst if non-
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// NULL. Updates fOffset and fBufferedSoFar. Assumes that fOffset is
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// less than fBufferedSoFar, and size is greater than 0.
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size_t bufferAndWriteTo(char* dst, size_t size);
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// Read up to size bytes directly from the stream and into dst if non-
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// NULL. Updates fOffset. Assumes fOffset is at or beyond the buffered
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// data, and size is greater than 0.
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size_t readDirectlyFromStream(char* dst, size_t size);
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typedef SkStream INHERITED;
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};
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