Move Courgette...

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 "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_