Updates to Brotli compression format, decoder and encoder

This commit contains a batch of changes that were made to the Brotli
compression algorithm in the last three weeks. Most important changes:

  * Added UTF8 context model for good text compression.
  * Simplified context modeling by having only 4 context modes.
  * Per-block context mode selection.
  * Faster backward copying and bit reading functions.
  * More efficient histogram coding.
  * Streaming support for the decoder and encoder.

brotli/dec/streams.h

@@ -0,0 +1,102 @@
+// Copyright 2013 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+// Functions for streaming input and output.
+
+#ifndef BROTLI_DEC_STREAMS_H_
+#define BROTLI_DEC_STREAMS_H_
+
+#include <stdio.h>
+#include "./types.h"
+
+#if defined(__cplusplus) || defined(c_plusplus)
+extern "C" {
+#endif
+
+// Function pointer type used to read len bytes into buf. Returns the
+// number of bytes read or -1 on error.
+typedef int (*BrotliInputFunction)(void* data, uint8_t* buf, size_t len);
+
+// Input callback function with associated data.
+typedef struct {
+  BrotliInputFunction cb_;
+  void* data_;
+} BrotliInput;
+
+// Reads len bytes into buf, using the in callback.
+static BROTLI_INLINE int BrotliRead(BrotliInput in, uint8_t* buf, size_t len) {
+  return in.cb_(in.data_, buf, len);
+}
+
+// Function pointer type used to write len bytes into buf. Returns the
+// number of bytes written or -1 on error.
+typedef int (*BrotliOutputFunction)(void* data, const uint8_t* buf, size_t len);
+
+// Output callback function with associated data.
+typedef struct {
+  BrotliOutputFunction cb_;
+  void* data_;
+} BrotliOutput;
+
+// Writes len bytes into buf, using the out callback.
+static BROTLI_INLINE int BrotliWrite(BrotliOutput out,
+                                     const uint8_t* buf, size_t len) {
+  return out.cb_(out.data_, buf, len);
+}
+
+// Memory region with position.
+typedef struct {
+  const uint8_t* buffer;
+  size_t length;
+  size_t pos;
+} BrotliMemInput;
+
+// Input callback where *data is a BrotliMemInput struct.
+int BrotliMemInputFunction(void* data, uint8_t* buf, size_t count);
+
+// Returns an input callback that wraps the given memory region.
+BrotliInput BrotliInitMemInput(const uint8_t* buffer, size_t length,
+                               BrotliMemInput* mem_input);
+
+// Output buffer with position.
+typedef struct {
+  uint8_t* buffer;
+  size_t length;
+  size_t pos;
+} BrotliMemOutput;
+
+// Output callback where *data is a BrotliMemOutput struct.
+int BrotliMemOutputFunction(void* data, const uint8_t* buf, size_t count);
+
+// Returns an output callback that wraps the given memory region.
+BrotliOutput BrotliInitMemOutput(uint8_t* buffer, size_t length,
+                                 BrotliMemOutput* mem_output);
+
+// Input callback that reads from standard input.
+int BrotliStdinInputFunction(void* data, uint8_t* buf, size_t count);
+BrotliInput BrotliStdinInput();
+
+// Output callback that writes to standard output.
+int BrotliStdoutOutputFunction(void* data, const uint8_t* buf, size_t count);
+BrotliOutput BrotliStdoutOutput();
+
+// Output callback that writes to a file.
+int BrotliFileOutputFunction(void* data, const uint8_t* buf, size_t count);
+BrotliOutput BrotliFileOutput(FILE* f);
+
+#if defined(__cplusplus) || defined(c_plusplus)
+}    // extern "C"
+#endif
+
+#endif  // BROTLI_DEC_STREAMS_H_