122 lines
4.2 KiB
C++
122 lines
4.2 KiB
C++
#ifndef GZIP_HPP_DECOMPRESS_HPP
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#define GZIP_HPP_DECOMPRESS_HPP
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#ifndef ZLIB_CONST
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#define ZLIB_CONST
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#endif
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// zlib
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#include <zlib.h>
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// std
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#include <limits>
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#include <stdexcept>
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#include <string>
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namespace gzip {
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inline void decompress(const char* data,
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std::size_t size,
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std::string& output,
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std::size_t max_uncompressed_size = 0,
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std::size_t buffering_size = 0)
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{
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if (buffering_size == 0)
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{
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buffering_size = (size * 2) - (size / 2) + 16;
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}
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z_stream inflate_s;
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inflate_s.zalloc = Z_NULL;
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inflate_s.zfree = Z_NULL;
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inflate_s.opaque = Z_NULL;
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inflate_s.avail_in = 0;
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inflate_s.next_in = Z_NULL;
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// The windowBits parameter is the base two logarithm of the window size (the size of the history buffer).
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// It should be in the range 8..15 for this version of the library.
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// Larger values of this parameter result in better compression at the expense of memory usage.
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// This range of values also changes the decoding type:
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// -8 to -15 for raw deflate
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// 8 to 15 for zlib
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// (8 to 15) + 16 for gzip
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// (8 to 15) + 32 to automatically detect gzip/zlib header
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constexpr int window_bits = 15 + 32; // auto with windowbits of 15
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constexpr unsigned int max_uint = std::numeric_limits<unsigned int>::max();
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const unsigned int size_step = buffering_size > max_uint ? max_uint : static_cast<unsigned int>(buffering_size);
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if( max_uncompressed_size != 0 && size_step > max_uncompressed_size )
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{
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throw std::runtime_error(
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"buffer size used during decompression of gzip will use more memory then allowed, "
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"either increase the limit or reduce the buffer size" );
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}
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#ifdef __GNUC__
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#pragma GCC diagnostic push
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#pragma GCC diagnostic ignored "-Wold-style-cast"
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#endif
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if (inflateInit2(&inflate_s, window_bits) != Z_OK)
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{
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throw std::runtime_error("inflate init failed");
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}
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#ifdef __GNUC__
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#pragma GCC diagnostic pop
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#endif
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inflate_s.next_in = reinterpret_cast<z_const Bytef*>(data);
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inflate_s.avail_in = static_cast<unsigned int>(size);
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std::string buffer(static_cast<std::size_t>(size_step), char());
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do
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{
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inflate_s.avail_out = size_step;
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inflate_s.next_out = reinterpret_cast<Bytef*>(&buffer[0]);
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const int ret = inflate(&inflate_s, Z_FINISH);
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if (ret != Z_STREAM_END && ret != Z_OK && ret != Z_BUF_ERROR)
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{
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std::string error_msg = inflate_s.msg;
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inflateEnd(&inflate_s);
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throw std::runtime_error(error_msg);
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}
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if (max_uncompressed_size != 0 && (output.size() + size_step - inflate_s.avail_out) > max_uncompressed_size)
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{
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inflateEnd(&inflate_s);
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throw std::runtime_error("size of output string will use more memory then intended when decompressing");
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}
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output.append(buffer, 0, size_step - inflate_s.avail_out);
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} while (inflate_s.avail_out == 0);
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const int ret2 = inflateEnd(&inflate_s);
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if (ret2 != Z_OK)
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{
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throw std::runtime_error("Unexpected gzip decompression error, state of stream was inconsistent");
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}
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}
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inline void decompress(std::string const& input,
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std::string& output,
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std::size_t max_uncompressed_size = 0,
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std::size_t buffering_size = 0)
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{
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return decompress(input.data(), input.size(), output, max_uncompressed_size, buffering_size);
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}
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inline std::string decompress(const char* data,
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std::size_t size,
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std::size_t max_uncompressed_size = 0,
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std::size_t buffering_size = 0)
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{
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std::string output;
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decompress(data, size, output, max_uncompressed_size, buffering_size);
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return output;
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}
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inline std::string decompress(std::string const& input,
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std::size_t max_uncompressed_size = 0,
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std::size_t buffering_size = 0)
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{
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std::string output;
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decompress(input.data(), input.size(), output, max_uncompressed_size, buffering_size);
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return output;
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}
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} // namespace gzip
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#endif // GZIP_HPP_DECOMPRESS_HPP
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