| // Copyright 2013 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. |
| |
| #include "chrome/browser/metrics/compression_utils.h" |
| |
| #include <vector> |
| |
| #include "base/basictypes.h" |
| #include "third_party/zlib/zlib.h" |
| |
| namespace { |
| |
| // The difference in bytes between a zlib header and a gzip header. |
| const size_t kGzipZlibHeaderDifferenceBytes = 16; |
| |
| // Pass an integer greater than the following get a gzip header instead of a |
| // zlib header when calling deflateInit2_. |
| const int kWindowBitsToGetGzipHeader = 16; |
| |
| // 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 = 8; |
| |
| // This code is taken almost verbatim from third_party/zlib/compress.c. The only |
| // difference is deflateInit2_ is called which sets the window bits to be > 16. |
| // That causes a gzip header to be emitted rather than a zlib header. |
| int GzipCompressHelper(Bytef* dest, |
| uLongf* dest_length, |
| const Bytef* source, |
| uLong source_length) { |
| z_stream stream; |
| |
| stream.next_in = bit_cast<Bytef*>(source); |
| stream.avail_in = static_cast<uInt>(source_length); |
| stream.next_out = dest; |
| stream.avail_out = static_cast<uInt>(*dest_length); |
| if (static_cast<uLong>(stream.avail_out) != *dest_length) |
| return Z_BUF_ERROR; |
| |
| stream.zalloc = static_cast<alloc_func>(0); |
| stream.zfree = static_cast<free_func>(0); |
| stream.opaque = static_cast<voidpf>(0); |
| |
| gz_header gzip_header; |
| memset(&gzip_header, 0, sizeof(gzip_header)); |
| int err = deflateInit2_(&stream, |
| Z_DEFAULT_COMPRESSION, |
| Z_DEFLATED, |
| MAX_WBITS + kWindowBitsToGetGzipHeader, |
| kZlibMemoryLevel, |
| Z_DEFAULT_STRATEGY, |
| ZLIB_VERSION, |
| sizeof(z_stream)); |
| if (err != Z_OK) |
| return err; |
| |
| err = deflateSetHeader(&stream, &gzip_header); |
| if (err != Z_OK) |
| return err; |
| |
| err = deflate(&stream, Z_FINISH); |
| if (err != Z_STREAM_END) { |
| deflateEnd(&stream); |
| return err == Z_OK ? Z_BUF_ERROR : err; |
| } |
| *dest_length = stream.total_out; |
| |
| err = deflateEnd(&stream); |
| return err; |
| } |
| } // namespace |
| |
| namespace chrome { |
| |
| bool GzipCompress(const std::string& input, std::string* output) { |
| std::vector<Bytef> compressed_data(kGzipZlibHeaderDifferenceBytes + |
| compressBound(input.size())); |
| |
| uLongf compressed_size = compressed_data.size(); |
| if (GzipCompressHelper(&compressed_data.front(), |
| &compressed_size, |
| bit_cast<const Bytef*>(input.data()), |
| input.size()) != Z_OK) |
| return false; |
| |
| compressed_data.resize(compressed_size); |
| output->assign(compressed_data.begin(), compressed_data.end()); |
| return true; |
| } |
| } // namespace chrome |