IXWebSocket/ixwebsocket/IXGzipCodec.cpp

/*
 *  IXGzipCodec.cpp
 *  Author: Benjamin Sergeant
 *  Copyright (c) 2020 Machine Zone, Inc. All rights reserved.
 */

#include "IXGzipCodec.h"

#include "IXBench.h"
#include <array>
#include <string.h>

#ifdef IXWEBSOCKET_USE_ZLIB
#include <zlib.h>
#endif

#ifdef IXWEBSOCKET_USE_DEFLATE
#include <libdeflate.h>
#endif

namespace ix
{
#ifdef IXWEBSOCKET_USE_ZLIB
    std::string gzipCompress(const std::string& str)
    {
#ifdef IXWEBSOCKET_USE_DEFLATE
        int compressionLevel = 6;
        struct libdeflate_compressor* compressor;

        compressor = libdeflate_alloc_compressor(compressionLevel);

        const void* uncompressed_data = str.data();
        size_t uncompressed_size = str.size();
        void* compressed_data;
        size_t actual_compressed_size;
        size_t max_compressed_size;

        max_compressed_size = libdeflate_gzip_compress_bound(compressor, uncompressed_size);
        compressed_data = malloc(max_compressed_size);

        if (compressed_data == NULL)
        {
            return std::string();
        }

        actual_compressed_size = libdeflate_gzip_compress(
            compressor, uncompressed_data, uncompressed_size, compressed_data, max_compressed_size);

        libdeflate_free_compressor(compressor);

        if (actual_compressed_size == 0)
        {
            free(compressed_data);
            return std::string();
        }

        std::string out;
        out.assign(reinterpret_cast<char*>(compressed_data), actual_compressed_size);
        free(compressed_data);

        return out;
#else
        z_stream zs; // z_stream is zlib's control structure
        memset(&zs, 0, sizeof(zs));

        // deflateInit2 configure the file format: request gzip instead of deflate
        const int windowBits = 15;
        const int GZIP_ENCODING = 16;

        deflateInit2(&zs,
                     Z_DEFAULT_COMPRESSION,
                     Z_DEFLATED,
                     windowBits | GZIP_ENCODING,
                     8,
                     Z_DEFAULT_STRATEGY);

        zs.next_in = (Bytef*) str.data();
        zs.avail_in = (uInt) str.size(); // set the z_stream's input

        int ret;
        char outbuffer[32768];
        std::string outstring;

        // retrieve the compressed bytes blockwise
        do
        {
            zs.next_out = reinterpret_cast<Bytef*>(outbuffer);
            zs.avail_out = sizeof(outbuffer);

            ret = deflate(&zs, Z_FINISH);

            if (outstring.size() < zs.total_out)
            {
                // append the block to the output string
                outstring.append(outbuffer, zs.total_out - outstring.size());
            }
        } while (ret == Z_OK);

        deflateEnd(&zs);

        return outstring;
#endif
    }

#ifdef IXWEBSOCKET_USE_DEFLATE
    static uint32_t loadDecompressedGzipSize(const uint8_t* p)
    {
        return ((uint32_t) p[0] << 0) | ((uint32_t) p[1] << 8) | ((uint32_t) p[2] << 16) |
               ((uint32_t) p[3] << 24);
    }
#endif

    bool gzipDecompress(const std::string& in, std::string& out)
    {
#ifdef IXWEBSOCKET_USE_DEFLATE
        struct libdeflate_decompressor* decompressor;
        decompressor = libdeflate_alloc_decompressor();

        const void* compressed_data = in.data();
        size_t compressed_size = in.size();

        // Retrieve uncompressed size from the trailer of the gziped data
        const uint8_t* ptr = reinterpret_cast<const uint8_t*>(&in.front());
        auto uncompressed_size = loadDecompressedGzipSize(&ptr[compressed_size - 4]);

        // Use it to redimension our output buffer
        out.resize(uncompressed_size);

        libdeflate_result result = libdeflate_gzip_decompress(
            decompressor, compressed_data, compressed_size, &out.front(), uncompressed_size, NULL);

        libdeflate_free_decompressor(decompressor);
        return result == LIBDEFLATE_SUCCESS;
#else
        z_stream inflateState;
        memset(&inflateState, 0, sizeof(inflateState));

        inflateState.zalloc = Z_NULL;
        inflateState.zfree = Z_NULL;
        inflateState.opaque = Z_NULL;
        inflateState.avail_in = 0;
        inflateState.next_in = Z_NULL;

        if (inflateInit2(&inflateState, 16 + MAX_WBITS) != Z_OK)
        {
            return false;
        }

        inflateState.avail_in = (uInt) in.size();
        inflateState.next_in = (unsigned char*) (const_cast<char*>(in.data()));

        const int kBufferSize = 1 << 14;
        std::array<unsigned char, kBufferSize> compressBuffer;

        do
        {
            inflateState.avail_out = (uInt) kBufferSize;
            inflateState.next_out = &compressBuffer.front();

            int ret = inflate(&inflateState, Z_SYNC_FLUSH);

            if (ret == Z_NEED_DICT || ret == Z_DATA_ERROR || ret == Z_MEM_ERROR)
            {
                inflateEnd(&inflateState);
                return false;
            }

            out.append(reinterpret_cast<char*>(&compressBuffer.front()),
                       kBufferSize - inflateState.avail_out);
        } while (inflateState.avail_out == 0);

        inflateEnd(&inflateState);
        return true;
#endif
    }
#endif
} // namespace ix