EVOLUTION-MANAGER

Edit File: zlib_compression_options.h

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
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==============================================================================*/

#ifndef TENSORFLOW_CORE_LIB_IO_ZLIB_COMPRESSION_OPTIONS_H_
#define TENSORFLOW_CORE_LIB_IO_ZLIB_COMPRESSION_OPTIONS_H_

#include "tensorflow/core/platform/types.h"

namespace tensorflow {
namespace io {

class ZlibCompressionOptions {
 public:
  ZlibCompressionOptions();

static ZlibCompressionOptions DEFAULT();
  static ZlibCompressionOptions RAW();
  static ZlibCompressionOptions GZIP();

// Defaults to Z_NO_FLUSH
  int8 flush_mode;

// Size of the buffer used for caching the data read from source file.
  int64 input_buffer_size = 256 << 10;

// Size of the sink buffer where the compressed/decompressed data produced by
  // zlib is cached.
  int64 output_buffer_size = 256 << 10;

// The window_bits parameter is the base two logarithm of the window size
  // (the size of the history buffer). Larger values of buffer size result in
  // better compression at the expense of memory usage.
  //
  // Accepted values:
  //
  // 8..15:
  // Normal deflate with zlib header and checksum.
  //
  // -8..-15:
  // Negative values can be used for raw deflate/inflate. In this case,
  // -window_bits determines the window size. deflate() will then generate raw
  // deflate data  with no zlib header or trailer, and will not compute an
  // adler32 check value. inflate() will then process raw deflate data, not
  // looking for a zlib or gzip header, not generating a check value, and not
  // looking for any check values for comparison at the end of the stream.
  //
  // 16 + [8..15]:
  // window_bits can also be greater than 15 for optional gzip encoding. Add 16
  // to window_bits to write a simple gzip header and trailer around the
  // compressed data instead of a zlib wrapper. The gzip header will have no
  // file name, no extra data, no comment, no modification time (set to zero),
  // no header crc, and the operating system will be set to 255 (unknown). If a
  // gzip stream is being written, strm->adler is a crc32 instead of an adler32.
  //
  // 0:
  // window_bits can also be zero to request that inflate use the window size
  // in the zlib header of the compressed stream.
  //
  // While inflating, window_bits must be greater than or equal to the
  // window_bits value provided used while compressing. If a compressed stream
  // with a larger window size is given as input, inflate() will return with the
  // error code Z_DATA_ERROR instead of trying to allocate a larger window.
  //
  // Defaults to MAX_WBITS
  int8 window_bits;

// From the zlib manual (http://www.zlib.net/manual.html):
  // The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:
  // 1 gives best speed, 9 gives best compression, 0 gives no compression at all
  // (the input data is simply copied a block at a time). Z_DEFAULT_COMPRESSION
  // requests a default compromise between speed and compression (currently
  // equivalent to level 6).
  int8 compression_level;

// Only Z_DEFLATED is supported at this time.
  int8 compression_method;

// From the zlib manual (http://www.zlib.net/manual.html):
  // The mem_level parameter specifies how much memory should be allocated for
  // the internal compression state. mem_level=1 uses minimum memory but is slow
  // and reduces compression ratio; mem_level=9 uses maximum memory for optimal
  // speed. The default value is 8.
  int8 mem_level = 9;

// From the zlib manual (http://www.zlib.net/manual.html):
  // The strategy parameter is used to tune the compression algorithm. Use the
  // value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by
  // a filter (or predictor), Z_HUFFMAN_ONLY to force Huffman encoding only
  // (no string match), or Z_RLE to limit match distances to one
  // (run-length encoding). Filtered data consists mostly of small values with
  // a somewhat random distribution. In this case, the compression algorithm is
  // tuned to compress them better. The effect of Z_FILTERED is to force more
  // Huffman coding and less string matching; it is somewhat intermediate
  // between Z_DEFAULT_STRATEGY and Z_HUFFMAN_ONLY. Z_RLE is designed to be
  // almost as fast as Z_HUFFMAN_ONLY, but give better compression for
  // PNG image data. The strategy parameter only affects the compression ratio
  // but not the correctness of the compressed output even if it is not set
  // appropriately. Z_FIXED prevents the use of dynamic Huffman codes, allowing
  // for a simpler decoder for special applications.
  int8 compression_strategy;

// When this is set to true and we are unable to find the header to correctly
  // decompress a file, we return an error when `ReadNBytes` is called instead
  // of CHECK-failing. Defaults to false (i.e. CHECK-failing).
  //
  // This option is ignored for `ZlibOutputBuffer`.
  bool soft_fail_on_error = false;  // NOLINT
};

inline ZlibCompressionOptions ZlibCompressionOptions::DEFAULT() {
  return ZlibCompressionOptions();
}

inline ZlibCompressionOptions ZlibCompressionOptions::RAW() {
  ZlibCompressionOptions options = ZlibCompressionOptions();
  options.window_bits = -options.window_bits;
  return options;
}

inline ZlibCompressionOptions ZlibCompressionOptions::GZIP() {
  ZlibCompressionOptions options = ZlibCompressionOptions();
  options.window_bits = options.window_bits + 16;
  return options;
}

}  // namespace io
}  // namespace tensorflow

#endif  // TENSORFLOW_CORE_LIB_IO_ZLIB_COMPRESSION_OPTIONS_H_