Class: TDriver::Checksum

Inherits:
Object show all
Defined in:
lib/tdriver/util/common/crc16.rb,
ext/native_extensions.c

Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.crc16(*args) ⇒ Object

static VALUE crc16_ibm( VALUE self, VALUE string ) 

// verify argument type
Check_Type( string, T_STRING );

const char* data = RSTRING_PTR( string );

int len = RSTRING_LEN( string );

int crc = 0xffff;

int c = 0;

while( len-- != 0 ){

  c = *data++;

crc = ( ( crc >> 4 ) & 0x0fff ) ^ CRC_16[ ( ( crc ^ c ) & 15 ) ];

crc = ( ( crc >> 4 ) & 0x0fff ) ^ CRC_16[ ( ( crc ^ ( c >> 4 )) & 15 ) ];

return INT2FIX( ~crc & 0xffff );

}



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# File 'ext/native_extensions.c', line 100

static VALUE crc16( int argc, VALUE* argv, VALUE self ) { 

/*

  # CRC-16-CCITT    
  def crc16( buf, crc = 0 )

    # calculate the checksum
    buf.each_byte{ | x | crc = ( ( crc << 8 ) ^ @CCITT_16[ ( crc >> 8 ) ^ x ] ) & 0xffff }

    # result
    crc

  end # crc16

*/

  // variables for arguments
  VALUE string, initial_crc;

  // retrieve arguments
  rb_scan_args(argc, argv, "11", &string, &initial_crc);

  // verify argument type
  Check_Type( string, T_STRING );

  // initialize crc 
  unsigned int crc = 0; 
  
  if (!NIL_P(initial_crc)){

    // verify initial crc value
    Check_Type( initial_crc, T_FIXNUM );
  
    crc = FIX2INT( initial_crc );
  
  }

  const unsigned char* data = RSTRING_PTR( string );
  
  unsigned int len = RSTRING_LEN( string );
  
  unsigned char c = 0;

  while( len-- ){

    c = *data++;

    crc = ( ( crc << 8 ) ^ CCITT_16[ ( crc >> 8 ) ^ c ] ) & 0xffff;

  }

	return INT2FIX( crc );


}

.crc16_ibm(*args) ⇒ Object

checksum methods



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# File 'ext/native_extensions.c', line 157

static VALUE crc16_ibm( int argc, VALUE* argv, VALUE self ) { 

/*

  # IBM-CRC-16: fallback when native extensions are not supported (e.g. jruby)
  def crc16_ibm( buf, crc = 0xffff )

    buf.each_byte do | c |

      crc = ( ( crc >> 4 ) & 0x0fff ) ^ @IBM_16[ ( ( crc ^ c ) & 15 ) ]

      crc = ( ( crc >> 4 ) & 0x0fff ) ^ @IBM_16[ ( ( crc ^ ( c >> 4 ) ) & 15 ) ]

    end

    # result
    ~crc & 0xffff

  end # crc16_ibm

*/

  // variables for arguments
  VALUE string, initial_crc;

  // retrieve arguments
  rb_scan_args(argc, argv, "11", &string, &initial_crc);

  unsigned int crc = 0xffff; 
  
  if (!NIL_P(initial_crc)){

    // verify initial crc value
    Check_Type( initial_crc, T_FIXNUM );
  
    crc = FIX2INT( initial_crc );
  
  }
  
  // verify argument type
  Check_Type( string, T_STRING );

  const unsigned char* data = RSTRING_PTR( string );
  
  unsigned int len = RSTRING_LEN( string );
  
  unsigned char c = 0;

  while( len-- ){

    c = *data++;

    crc = ( crc >> 4 ) ^ CRC_16[ ( crc ^ c ) & 15 ];
              
    crc = ( crc >> 4 ) ^ CRC_16[ ( crc ^ ( c >> 4 ) ) & 15 ];

  }

	return INT2FIX( ~crc & 0xffff );


}

.native_extension ⇒ Object

determines that native extension is in use



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# File 'ext/native_extensions.c', line 221

static VALUE native_extension( VALUE self ) { 

  return Qtrue;

}

Instance Method Details

#crc16(buf, crc = 0) ⇒ Object

CRC-16-CCITT



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# File 'lib/tdriver/util/common/crc16.rb', line 80

def crc16( buf, crc = 0 )

  # calculate the checksum
  buf.each_byte{ | x | crc = ( ( crc << 8 ) ^ @CCITT_16[ ( crc >> 8 ) ^ x ] ) & 0xffff }

  # result
  crc

end

#crc16_ibm(buf, crc = 0xffff) ⇒ Object

IBM-CRC-16: fallback when native extensions are not supported (e.g. jruby)



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# File 'lib/tdriver/util/common/crc16.rb', line 98

def crc16_ibm( buf, crc = 0xffff )

  buf.each_byte do | c |

    crc = ( ( crc >> 4 ) & 0x0fff ) ^ @IBM_16[ ( ( crc ^ c ) & 15 ) ]

    crc = ( ( crc >> 4 ) & 0x0fff ) ^ @IBM_16[ ( ( crc ^ ( c >> 4 ) ) & 15 ) ]

  end

  # result
  ~crc & 0xffff

end

#native_extension ⇒ Object

determines that native extension is not in use



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# File 'lib/tdriver/util/common/crc16.rb', line 91

def native_extension

  false

end