sapphire/deps/datReader/crc32.cpp

#include "crc32.h"

#include <mutex>
#include <vector>

#include <zlib/zlib.h>

namespace internal
{
    // Mutex to prevent two threads from concurrently trying to build the crc tables atthe same time
    std::mutex crc_creation_mutex;

    typedef std::vector<uint32_t> CrcTable;
    
    // Our crc/rev_crc tables
    CrcTable crc_table;
    CrcTable rev_crc_table;

    bool crc_tables_created = false;

    void build_crc_tables()
    {
        std::lock_guard<std::mutex> lock(crc_creation_mutex);
        if (!crc_tables_created)
        {
            crc_table.resize(0x100);
            rev_crc_table.resize(0x100);
            for (auto i = 0; i < 0x100; ++i)
            {
                uint32_t crc = i;
                for (auto j = 0; j < 8; ++j)
                {
                    if (crc & 1)
                    {
                        crc = 0xEDB88320 ^ (crc >> 1);
                    }
                    else
                    {
                        crc = crc >> 1;
                    }
                }
                crc_table[i] = crc;
                rev_crc_table[crc >> 24] = i + ((crc & 0xFFFFFF) << 8);
            }
        }
        crc_tables_created = true;
    }

    const CrcTable& get_crc_table()
    {
        if (!crc_tables_created)
        {
            build_crc_tables();
        }
        return crc_table;
    }

    const CrcTable& get_rev_crc_table()
    {
        if (!crc_tables_created)
        {
            build_crc_tables();
        }
        return rev_crc_table;
    }
}

namespace xiv::utils::crc32
{

  uint32_t compute( const std::string& i_input, uint32_t init_crc )
  {
    // Classical crc stuff
    auto& crc_table = internal::get_crc_table();
    auto crc = init_crc;
    for( std::size_t i = 0; i < i_input.size(); ++i )
    {
      crc = crc_table[ ( crc ^ i_input[ i ] ) & 0xFF ] ^ ( crc >> 8 );
    }
    return crc;
  }

  uint32_t rev_compute( const std::string& i_input, uint32_t init_crc )
  {
    auto& rev_crc_table = internal::get_rev_crc_table();
    auto crc = init_crc;
    const auto input_size = i_input.size();
    // Reverse crc
    for( auto i = input_size; i > 0; --i )
    {
      crc = rev_crc_table[ crc >> 24 ] ^ ( ( crc << 8 ) & 0xFFFFFF00 ) ^ i_input[ input_size - i - 1 ];
    }
    // Compute the 4 bytes needed for this init_crc
    for( auto i = 0; i < 4; ++i )
    {
      crc = rev_crc_table[ crc >> 24 ] ^ ( ( crc << 8 ) & 0xFFFFFF00 );
    }
    return crc;
  }

  void generate_hashes_1( std::string& i_format, const uint32_t i_first_index, std::vector< uint32_t >& o_hashes )
  {
    char* str = const_cast<char*>(i_format.data());
    const uint32_t str_size = i_format.size();

    o_hashes.resize( 10000 );

    uint32_t i = 0;
    for( char a = '0'; a <= '9'; ++a )
    {
      str[ i_first_index ] = a;
      for( char b = '0'; b <= '9'; ++b )
      {
        str[ i_first_index + 1 ] = b;
        for( char c = '0'; c <= '9'; ++c )
        {
          str[ i_first_index + 2 ] = c;
          for( char d = '0'; d <= '9'; ++d )
          {
            str[ i_first_index + 3 ] = d;
            o_hashes[ i ] = ::crc32( 0, reinterpret_cast<uint8_t*>(&( str[ 0 ] )), str_size ) ^ 0xFFFFFFFF;
            ++i;
          }
        }
      }
    }
  }

  void generate_hashes_2( std::string& i_format, const uint32_t i_first_index, const uint32_t i_second_index,
                          std::vector< uint32_t >& o_hashes )
  {
    char* str = const_cast<char*>(i_format.data());
    const uint32_t str_size = i_format.size();

    o_hashes.resize( 100000000 );

    uint32_t i = 0;
    for( char a = '0'; a <= '9'; ++a )
    {
      str[ i_first_index ] = a;
      for( char b = '0'; b <= '9'; ++b )
      {
        str[ i_first_index + 1 ] = b;
        for( char c = '0'; c <= '9'; ++c )
        {
          str[ i_first_index + 2 ] = c;
          for( char d = '0'; d <= '9'; ++d )
          {
            str[ i_first_index + 3 ] = d;
            for( char e = '0'; e <= '9'; ++e )
            {
              str[ i_second_index ] = e;
              for( char f = '0'; f <= '9'; ++f )
              {
                str[ i_second_index + 1 ] = f;
                for( char g = '0'; g <= '9'; ++g )
                {
                  str[ i_second_index + 2 ] = g;
                  for( char h = '0'; h <= '9'; ++h )
                  {
                    str[ i_second_index + 3 ] = h;
                    o_hashes[ i ] = ::crc32( 0, reinterpret_cast<uint8_t*>(&( str[ 0 ] )), str_size ) ^ 0xFFFFFFFF;
                    ++i;
                  }
                }
              }
            }
          }
        }
      }
    }
  }


}