compression_utils_portable.cc | Explore in Territory

/* compression_utils_portable.cc
 *
 * Copyright 2019 The Chromium Authors
 * Use of this source code is governed by a BSD-style license that can be
 * found in the Chromium source repository LICENSE file.
 */

#include "compression_utils_portable.h"

#include <stddef.h>
#include <stdlib.h>
#include <string.h>

namespace zlib_internal {

// The difference in bytes between a zlib header and a gzip header.
const size_t kGzipZlibHeaderDifferenceBytes = …;

// Pass an integer greater than the following get a gzip header instead of a
// zlib header when calling deflateInit2() and inflateInit2().
const int kWindowBitsToGetGzipHeader = …;

// This describes the amount of memory zlib uses to compress data. It can go
// from 1 to 9, with 8 being the default. For details, see:
// http://www.zlib.net/manual.html (search for memLevel).
const int kZlibMemoryLevel = …;

// The expected compressed size is based on the input size factored by
// internal Zlib constants (e.g. window size, etc) plus the wrapper
// header size.
uLongf GzipExpectedCompressedSize(uLongf input_size) { … }

// The expected decompressed size is stored in the last
// 4 bytes of |input| in LE. See https://tools.ietf.org/html/rfc1952#page-5
uint32_t GetGzipUncompressedSize(const Bytef* compressed_data, size_t length) { … }

// The number of window bits determines the type of wrapper to use - see
// https://cs.chromium.org/chromium/src/third_party/zlib/zlib.h?l=566
inline int ZlibStreamWrapperType(WrapperType type) { … }

int GzipCompressHelper(Bytef* dest,
                       uLongf* dest_length,
                       const Bytef* source,
                       uLong source_length,
                       void* (*malloc_fn)(size_t),
                       void (*free_fn)(void*)) { … }

// This code is taken almost verbatim from third_party/zlib/compress.c. The only
// difference is deflateInit2() is called which allows different window bits to
// be set. > 16 causes a gzip header to be emitted rather than a zlib header,
// and negative causes no header to emitted.
//
// Compression level can be a number from 1-9, with 1 being the fastest, 9 being
// the best compression. The default, which the GZIP helper uses, is 6.
int CompressHelper(WrapperType wrapper_type,
                   Bytef* dest,
                   uLongf* dest_length,
                   const Bytef* source,
                   uLong source_length,
                   int compression_level,
                   void* (*malloc_fn)(size_t),
                   void (*free_fn)(void*)) { … }

int GzipUncompressHelper(Bytef* dest,
                         uLongf* dest_length,
                         const Bytef* source,
                         uLong source_length) { … }

// This code is taken almost verbatim from third_party/zlib/uncompr.c. The only
// difference is inflateInit2() is called which allows different window bits to
// be set. > 16 causes a gzip header to be emitted rather than a zlib header,
// and negative causes no header to emitted.
int UncompressHelper(WrapperType wrapper_type,
                     Bytef* dest,
                     uLongf* dest_length,
                     const Bytef* source,
                     uLong source_length) { … }

}  // namespace zlib_internal
chromium/third_party/zlib/google/compression_utils_portable.cc
