Move Courgette...

third_party/courgette/streams.h

-// Copyright (c) 2009 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// Streams classes.
-//
-// These memory-resident streams are used for serialzing data into a sequential
-// region of memory.
-// Streams are divided into SourceStreams for reading and SinkStreams for
-// writing.  Streams are aggregated into Sets which allows several streams to be
-// used at once.  Example: we can write A1, B1, A2, B2 but achive the memory
-// layout A1 A2 B1 B2 by writing 'A's to one stream and 'B's to another.
-#ifndef COURGETTE_STREAMS_H_
-#define COURGETTE_STREAMS_H_
-
-#include <stdio.h>  // for FILE*
-#include <string>
-
-#include "base/basictypes.h"
-
-#include "third_party/courgette/region.h"
-
-namespace courgette {
-
-class SourceStream;
-class SinkStream;
-
-// Maximum number of streams in a stream set.
-static const unsigned int kMaxStreams = 10;
-
-// A SourceStream allows a region of memory to be scanned by a sequence of Read
-// operations.  The stream does not own the memory.
-class SourceStream {
- public:
-  SourceStream() : start_(NULL), end_(NULL), current_(NULL) {}
-
-  // Initializes the SourceStream to yield the bytes at |pointer|.  The caller
-  // still owns the memory at |pointer| and should free the memory only after
-  // the last use of the stream.
-  void Init(const void* pointer, size_t length) {
-    start_ = static_cast<const uint8*>(pointer);
-    end_ = start_ + length;
-    current_ = start_;
-  }
-
-  // Initializes the SourceStream to yield the bytes in |region|.  The caller
-  // still owns the memory at |region| and should free the memory only after
-  // the last use of the stream.
-  void Init(const Region& region) { Init(region.start(), region.length()); }
-
-  // Initializes the SourceStream to yield the bytes in |string|.  The caller
-  // still owns the memory at |string| and should free the memory only after
-  // the last use of the stream.
-  void Init(const std::string& string) { Init(string.c_str(), string.size()); }
-
-  // Initializes the SourceStream to yield the bytes written to |sink|. |sink|
-  // still owns the memory, so needs to outlive |this|.  |sink| should not be
-  // written to after |this| is initialized.
-  void Init(const SinkStream& sink);
-
-  // Returns number of bytes remaining to be read from stream.
-  size_t Remaining() const { return end_ - current_; }
-
-  // Returns initial length of stream before any data consumed by reading.
-  size_t OriginalLength() const { return end_ - start_; }
-
-  const uint8* Buffer() const { return current_; }
-  bool Empty() const { return current_ == end_; }
-
-  // Copies bytes from stream to memory at |destination|.  Returns 'false' if
-  // insufficient data to satisfy request.
-  bool Read(void* destination, size_t byte_count);
-
-  // Reads a varint formatted unsigned integer from stream.  Returns 'false' if
-  // the read failed due to insufficient data or malformed Varint32.
-  bool ReadVarint32(uint32* output_value);
-
-  // Reads a varint formatted signed integer from stream.  Returns 'false' if
-  // the read failed due to insufficient data or malformed Varint32.
-  bool ReadVarint32Signed(int32* output_value);
-
-  // Initializes |substream| to yield |length| bytes from |this| stream,
-  // starting at |offset| bytes from the current position.  Returns 'false' if
-  // there are insufficient bytes in |this| stream.
-  bool ShareSubstream(size_t offset, size_t length, SourceStream* substream);
-
-  // Initializes |substream| to yield |length| bytes from |this| stream,
-  // starting at the current position.  Returns 'false' if there are
-  // insufficient bytes in |this| stream.
-  bool ShareSubstream(size_t length, SourceStream* substream) {
-    return ShareSubstream(0, length, substream);
-  }
-
-  // Reads |length| bytes from |this| stream.  Initializes |substream| to yield
-  // the bytes.  Returns 'false' if there are insufficient bytes in |this|
-  // stream.
-  bool ReadSubstream(size_t length, SourceStream* substream);
-
-  // Skips over bytes.  Returns 'false' if insufficient data to satisfy request.
-  bool Skip(size_t byte_count);
-
- private:
-  const uint8* start_;     // Points to start of buffer.
-  const uint8* end_;       // Points to first location after buffer.
-  const uint8* current_;   // Points into buffer at current read location.
-
-  DISALLOW_COPY_AND_ASSIGN(SourceStream);
-};
-
-// A SinkStream accumulates writes into a buffer that it owns.  The stream is
-// initialy in an 'accumulating' state where writes are permitted.  Accessing
-// the buffer moves the stream into a 'locked' state where no more writes are
-// permitted.  The stream may also be in a 'retired' state where the buffer
-// contents are no longer available.
-class SinkStream {
- public:
-  SinkStream() {}
-  ~SinkStream() {}
-
-  // Appends |byte_count| bytes from |data| to the stream.
-  void Write(const void* data, size_t byte_count);
-
-  // Appends the 'varint32' encoding of |value| to the stream.
-  void WriteVarint32(uint32 value);
-
-  // Appends the 'varint32' encoding of |value| to the stream.
-  void WriteVarint32Signed(int32 value);
-
-  // Contents of |other| are appended to |this| stream.  The |other| stream
-  // becomes retired.
-  void Append(SinkStream* other);
-
-  // Returns the number of bytes in this SinkStream
-  size_t Length() const { return buffer_.size(); }
-
-  // Returns a pointer to contiguously allocated Length() bytes in the stream.
-  // Writing to the stream invalidates the pointer.  The SinkStream continues to
-  // own the memory.
-  const uint8* Buffer() const {
-    return reinterpret_cast<const uint8*>(buffer_.c_str());
-  }
-
-  // Hints that the stream will grow by an additional |length| bytes.
-  void Reserve(size_t length) { buffer_.reserve(length + buffer_.length()); }
-
- private:
-  std::string buffer_;  // Use a string to manage the stream's memory.
-
-  DISALLOW_COPY_AND_ASSIGN(SinkStream);
-};
-
-// A SourceStreamSet is a set of SourceStreams.
-class SourceStreamSet {
- public:
-  SourceStreamSet();
-  ~SourceStreamSet();
-
-  // Initializes the SourceStreamSet with the stream data in memory at |source|.
-  // The caller continues to own the memory and should not modify or free the
-  // memory until the SourceStreamSet destructor has been called.
-  //
-  // The layout of the streams are as written by SinkStreamSet::CopyTo.
-  // Init returns 'false' if the layout is inconsistent with |byte_count|.
-  bool Init(const void* source, size_t byte_count);
-
-  // Initializes |this| from |source|.  The caller continues to own the memory
-  // because it continues to be owned by |source|.
-  bool Init(SourceStream* source);
-
-  // Returns a pointer to one of the sub-streams.
-  SourceStream* stream(size_t id) { return id < count_ ? &streams_[id] : NULL; }
-
-  // Initialize |set| from |this|.
-  bool ReadSet(SourceStreamSet* set);
-
-  // Returns 'true' if all streams are completely consumed.
-  bool Empty() const;
-
- private:
-  size_t count_;
-  SourceStream streams_[kMaxStreams];
-
-  DISALLOW_COPY_AND_ASSIGN(SourceStreamSet);
-};
-
-class SinkStreamSet {
- public:
-  SinkStreamSet();
-  ~SinkStreamSet();
-
-  // Initializes the SinkStreamSet to have |stream_index_limit| streams.  Must
-  // be <= kMaxStreams.  If Init is not called the default is has kMaxStream.
-  void Init(size_t stream_index_limit);
-
-  // Returns a pointer to a substream.
-  SinkStream* stream(size_t id) { return id < count_ ? &streams_[id] : NULL; }
-
-  // CopyTo serializes the streams in the SinkStreamSet into a single target
-  // stream or file.  The serialized format may be re-read by initializing a
-  // SourceStreamSet with a buffer containing the data.
-  bool CopyTo(SinkStream* combined_stream);
-  bool CopyToFile(FILE* file);
-  bool CopyToFileDescriptor(int file_descriptor);
-
-  // Writes the streams of |set| into the corresponding streams of |this|.
-  // Stream zero first has some metadata written to it.  |set| becomes retired.
-  // Partner to SourceStreamSet::ReadSet.
-  bool WriteSet(SinkStreamSet* set);
-
- private:
-  void CopyHeaderTo(SinkStream* stream);
-
-  size_t count_;
-  SinkStream streams_[kMaxStreams];
-
-  DISALLOW_COPY_AND_ASSIGN(SinkStreamSet);
-};
-
-}  // namespace
-#endif  // COURGETTE_STREAMS_H_