mirror of https://github.com/CrowCpp/Crow.git
100 lines
3.5 KiB
C++
100 lines
3.5 KiB
C++
#ifdef CROW_ENABLE_COMPRESSION
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#pragma once
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#include <string>
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#include <zlib.h>
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// http://zlib.net/manual.html
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namespace crow // NOTE: Already documented in "crow/app.h"
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{
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namespace compression
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{
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// Values used in the 'windowBits' parameter for deflateInit2.
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enum algorithm
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{
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// 15 is the default value for deflate
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DEFLATE = 15,
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// windowBits can also be greater than 15 for optional gzip encoding.
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// Add 16 to windowBits to write a simple gzip header and trailer around the compressed data instead of a zlib wrapper.
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GZIP = 15 | 16,
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};
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inline std::string compress_string(std::string const& str, algorithm algo)
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{
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std::string compressed_str;
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z_stream stream{};
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// Initialize with the default values
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if (::deflateInit2(&stream, Z_DEFAULT_COMPRESSION, Z_DEFLATED, algo, 8, Z_DEFAULT_STRATEGY) == Z_OK)
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{
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char buffer[8192];
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stream.avail_in = str.size();
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// zlib does not take a const pointer. The data is not altered.
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stream.next_in = const_cast<Bytef*>(reinterpret_cast<const Bytef*>(str.c_str()));
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int code = Z_OK;
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do
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{
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stream.avail_out = sizeof(buffer);
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stream.next_out = reinterpret_cast<Bytef*>(&buffer[0]);
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code = ::deflate(&stream, Z_FINISH);
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// Successful and non-fatal error code returned by deflate when used with Z_FINISH flush
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if (code == Z_OK || code == Z_STREAM_END)
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{
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std::copy(&buffer[0], &buffer[sizeof(buffer) - stream.avail_out], std::back_inserter(compressed_str));
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}
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} while (code == Z_OK);
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if (code != Z_STREAM_END)
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compressed_str.clear();
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::deflateEnd(&stream);
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}
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return compressed_str;
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}
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inline std::string decompress_string(std::string const& deflated_string)
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{
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std::string inflated_string;
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Bytef tmp[8192];
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z_stream zstream{};
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zstream.avail_in = deflated_string.size();
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// Nasty const_cast but zlib won't alter its contents
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zstream.next_in = const_cast<Bytef*>(reinterpret_cast<Bytef const*>(deflated_string.c_str()));
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// Initialize with automatic header detection, for gzip support
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if (::inflateInit2(&zstream, MAX_WBITS | 32) == Z_OK)
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{
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do
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{
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zstream.avail_out = sizeof(tmp);
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zstream.next_out = &tmp[0];
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auto ret = ::inflate(&zstream, Z_NO_FLUSH);
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if (ret == Z_OK || ret == Z_STREAM_END)
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{
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std::copy(&tmp[0], &tmp[sizeof(tmp) - zstream.avail_out], std::back_inserter(inflated_string));
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}
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else
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{
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// Something went wrong with inflate; make sure we return an empty string
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inflated_string.clear();
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break;
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}
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} while (zstream.avail_out == 0);
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// Free zlib's internal memory
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::inflateEnd(&zstream);
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}
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return inflated_string;
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}
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} // namespace compression
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} // namespace crow
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#endif
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