Gaudi::Utils::QuasiRandom Namespace Reference

Functions
uint32_t	mix (uint32_t state)
	Create a hash with a large avalanche effect from a 32 bit integer. More...
uint32_t	mix32 (uint32_t state, uint32_t extra)
	mix some 'extra' entropy into 'state' and return result More...
uint32_t	mix64 (uint32_t state, uint64_t extra)
	mix some 'extra' entropy into 'state' and return result More...
uint32_t	mixString (uint32_t state, const std::string &extra)
	mix some 'extra' entropy into 'state' and return result More...

Function Documentation

uint32_t Gaudi::Utils::QuasiRandom::mix

(

uint32_t

state

)

Create a hash with a large avalanche effect from a 32 bit integer.

Definition at line 14 of file QuasiRandom.cpp.

      {
        state += ( state << 16 );
        state ^= ( state >> 13 );
        state += ( state << 4 );
        state ^= ( state >> 7 );
        state += ( state << 10 );
        state ^= ( state >> 5 );
        state += ( state << 8 );
        state ^= ( state >> 16 );
        return state;
      }

uint32_t Gaudi::Utils::QuasiRandom::mix32	(	uint32_t	state,
		uint32_t	extra
	)

mix some 'extra' entropy into 'state' and return result

Definition at line 27 of file QuasiRandom.cpp.

{ return mix( state + extra ); }

uint32_t Gaudi::Utils::QuasiRandom::mix64	(	uint32_t	state,
		uint64_t	extra
	)

mix some 'extra' entropy into 'state' and return result

Definition at line 29 of file QuasiRandom.cpp.

      {
        typedef boost::low_bits_mask_t<32> mask_t;
        state = mix32( state, uint32_t( extra & mask_t::sig_bits_fast ) );
        return mix32( state, uint32_t( ( extra >> 32 ) & mask_t::sig_bits_fast ) );
      }

uint32_t Gaudi::Utils::QuasiRandom::mixString	(	uint32_t	state,
		const std::string &	extra
	)

mix some 'extra' entropy into 'state' and return result

Definition at line 36 of file QuasiRandom.cpp.

      {
        // prefix name with ' ' until the size is a multiple of 4.
        std::string s = std::string( ( 4 - extra.size() % 4 ) % 4, ' ' ) + extra;
        for ( size_t i = 0; i < s.size() / 4; ++i ) {
          // FIXME: this might do something different on big endian vs. small endian machines...
          uint32_t x = uint32_t( s[i * 4] ) | uint32_t( s[i * 4 + 1] ) << 8 | uint32_t( s[i * 4 + 2] ) << 16 |
                       uint32_t( s[i * 4 + 3] ) << 24;
          state = mix32( state, x );
        }
        return state;
      }