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  1. #include<fstream>
  2. #include<iostream>
  3. #include<numeric>
  4. #include<sstream>
  5. #include<zlib.h>
  6.  
  7. namespace Gzip
  8. {
  9.   using std::string;
  10.  
  11.   using UINT = uint32_t;
  12.   // Source: https://stackoverflow.com/questions/20734831/compress-string-with-gzip-using-qcompress
  13.   static const uint8_t s_Header[10] = {0x1f, 0x8b, 0x08, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x0b};
  14.  
  15.   static const UINT s_Crc[] =
  16.   { /* CRC polynomial 0xedb88320 */
  17.     0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419, 0x706af48f,
  18.     0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988,
  19.     0x09b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2,
  20.     0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7,
  21.     0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
  22.     0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
  23.     0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c,
  24.     0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59,
  25.     0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423,
  26.     0xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
  27.     0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, 0x01db7106,
  28.     0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f, 0x9fbfe4a5, 0xe8b8d433,
  29.     0x7807c9a2, 0x0f00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d,
  30.     0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e,
  31.     0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
  32.     0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65,
  33.     0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7,
  34.     0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
  35.     0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa,
  36.     0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
  37.     0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
  38.     0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x03b6e20c, 0x74b1d29a,
  39.     0xead54739, 0x9dd277af, 0x04db2615, 0x73dc1683, 0xe3630b12, 0x94643b84,
  40.     0x0d6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1,
  41.     0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
  42.     0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc,
  43.     0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e,
  44.     0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b,
  45.     0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55,
  46.     0x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
  47.     0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28,
  48.     0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d,
  49.     0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x026d930a, 0x9c0906a9, 0xeb0e363f,
  50.     0x72076785, 0x05005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38,
  51.     0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
  52.     0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
  53.     0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69,
  54.     0x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2,
  55.     0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc,
  56.     0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
  57.     0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693,
  58.     0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
  59.     0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d
  60.   };
  61.  
  62.   template<typename T>
  63.   UINT
  64.   GetCrc (const T& data)
  65.   {
  66.     return ~std::accumulate(data.begin(), data.end(), UINT(0xffffffff),
  67.                             [] (UINT crc, char ch)
  68.                             { return s_Crc[(crc ^ ((uint8_t)ch)) & 0xff] ^ ((crc) >> 8); });
  69.   }
  70.  
  71.   string
  72.   CompressContent (const string& content)
  73.   {
  74.     // Prepend a generic 10-byte gzip header (see RFC 1952),
  75.     std::ostringstream header, footer;
  76.     for(const auto& byte : s_Header)
  77.       header.put(byte);
  78.  
  79.     ::uLongf size = content.size() + 100;
  80.     auto gzip = header.str();
  81.     gzip.resize(size);
  82.     ::compress2(reinterpret_cast<Bytef*>(&gzip[0] + sizeof(s_Header)), &size,
  83.                 reinterpret_cast<const Bytef*>(content.data()), content.size(), -1);
  84.     gzip.resize(sizeof(s_Header) + size);
  85.  
  86.     // Append a four-byte CRC-32 of the uncompressed data
  87.     // Append 4 bytes uncompressed input size modulo 2^32
  88.     auto Serialize = [] (std::ostringstream& stream, const UINT value)
  89.                      { stream.put((value & 0x000000ff)).put((value & 0x0000ff00) >> 8)
  90.                              .put((value & 0x00ff0000) >> 16).put((value & 0xff000000) >> 24); };
  91.     footer.imbue(std::locale::classic());
  92.     Serialize(footer, GetCrc(content));
  93.     Serialize(footer, content.size());
  94.  
  95.     return gzip + footer.str();
  96.   }
  97.  
  98.   string
  99.   UncompressContent (const string& gzip)
  100.   {
  101.     auto* const pDataOrig = reinterpret_cast<const uint8_t*>(gzip.data());
  102.     for(size_t i = 0; i < sizeof(s_Header); ++i)
  103.       if(s_Header[i] != pDataOrig[i])
  104.         return {};
  105.  
  106.     const auto crc = *reinterpret_cast<const UINT*>(gzip.data() + gzip.size() -
  107.                                                     (2 * sizeof(UINT)));
  108.     ::uLongf size = *reinterpret_cast<const UINT*>(gzip.data() + gzip.size() -
  109.                                                    sizeof(UINT));
  110.     string content(size, 0);
  111.  
  112.     ::uncompress(reinterpret_cast<Bytef*>(&content[0]), &size,
  113.                  reinterpret_cast<const Bytef*>(gzip.data() + sizeof(s_Header)),
  114.                  gzip.size() - sizeof(s_Header) - (2 * sizeof(UINT)));
  115.     content.resize(size);
  116.  
  117.     if(crc != GetCrc(content))
  118.       return {};
  119.     return content;
  120.   }
  121. }
  122.  
  123. #define CONTENT "Hello world"
  124.  
  125. int main ()
  126. {
  127.   auto content = Gzip::CompressContent(CONTENT);
  128.   std::cout << CONTENT << "---" << content << "\n";
  129.   std::cout << "content1: " << Gzip::UncompressContent(content) << "\n";
  130.  
  131.   std::ofstream file("/home/milind/Desktop/test.txt.gz");
  132.   file.write(content.data(), content.size());
  133. }
  134.  
  135.  
Compilation error #stdin compilation error #stdout 0s 0KB
comments (?)
stdin 
Standard input is empty
compilation info 
/usr/bin/ld: /home/zXmSJm/ccQylTXM.o: in function `Gzip::UncompressContent(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)':
prog.cpp:(.text+0x94): undefined reference to `uncompress'
/usr/bin/ld: /home/zXmSJm/ccQylTXM.o: in function `Gzip::CompressContent(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)':
prog.cpp:(.text+0x4f9): undefined reference to `compress2'
collect2: error: ld returned 1 exit status
stdout 
Standard output is empty
https://ideone.com/SFTrvj
language:
C++14 (gcc 8.3)
created:
4 years ago
visibility:
public

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