src/pagespeed/kernel/util/gzip_inflater.h

/*
 * Copyright 2010 Google Inc.
 *
 * 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.
 */

// Author: bmcquade@google.com (Bryan McQuade)

#ifndef PAGESPEED_KERNEL_UTIL_GZIP_INFLATER_H_
#define PAGESPEED_KERNEL_UTIL_GZIP_INFLATER_H_

#include <cstddef>
#include "pagespeed/kernel/base/basictypes.h"
#include "pagespeed/kernel/base/string_util.h"

typedef struct z_stream_s z_stream;

namespace net_instaweb {

class Writer;

class GzipInflater {
 public:
  enum InflateType {kGzip, kDeflate};

  explicit GzipInflater(InflateType type);
  ~GzipInflater();

  // Should be called once, before inflating any data.
  bool Init();

  // Should be called once, after inflating is finished.
  void ShutDown();

  // Does the inflater still have input that has not yet been
  // consumed? If true, the caller should call InflateBytes(). If
  // false, the gzip inflater is ready for additional input.
  bool HasUnconsumedInput() const;

  // Pass a gzip-compressed buffer to the gzip inflater. The gzip
  // inflater will inflate the buffer via InflateBytes(). SetInput
  // should not be called if HasUnconsumedInput() is true, and the
  // buffer passed into SetInput should not be modified by the caller
  // until HasUnconsumedInput() returns false.
  bool SetInput(const void *in, size_t in_size);

  // Decompress the input passed in via SetInput. Should be called
  // until HasUnconsumedInput returns false. Returns the number of
  // bytes inflated, or -1 if an error was encountered while
  // inflating.
  int InflateBytes(char *buf, size_t buf_size);

  // Has the entire input been inflated?
  bool finished() const { return finished_; }

  // Was an error encountered during inflating?
  bool error() const { return error_; }

  // Deflates a stringpiece, writing output to Writer.  Returns false
  // if there was some kind of failure, though none are expected.
  static bool Deflate(StringPiece in, InflateType format, Writer* writer);
  static bool Deflate(StringPiece in, InflateType format, int compression_level,
                      Writer* writer);

  // Inflates a stringpiece, writing output to Writer.  Returns false
  // if there was some kind of failure, such as a corrupt input.
  static bool Inflate(StringPiece in, InflateType format, Writer* writer);

  // Checks whether in starts with the gzip file signature.
  static bool HasGzipMagicBytes(StringPiece in);

 private:
  friend class GzipInflaterTestPeer;

  enum StreamFormat {
    FORMAT_GZIP,         // RFC1952
    FORMAT_ZLIB_STREAM,  // RFC1950
    FORMAT_RAW_INFLATE,  // RFC1951
  };

  static bool GetWindowBitsForFormat(
      StreamFormat format, int* out_window_bits);
  void Free();
  void SetInputInternal(const void *in, size_t in_size);
  void SwitchToRawDeflateFormat();

  z_stream *zlib_;
  StreamFormat format_;
  bool finished_;
  bool error_;

  DISALLOW_COPY_AND_ASSIGN(GzipInflater);
};

}  // namespace net_instaweb

#endif  // PAGESPEED_KERNEL_UTIL_GZIP_INFLATER_H_