swap_lw_bytes(9r)														 swap_lw_bytes(9r)

NAME

       swap_lw_bytes, swap_word_bytes, swap_words - General: Perform byte-swapping operations

SYNOPSIS

       unsigned int swap_lw_bytes(
	       unsigned int buffer ); unsigned int swap_word_bytes(
	       unsigned int buffer ); unsigned int swap_words(
	       unsigned int buffer );

ARGUMENTS

       Specifies a 32-bit (4 bytes) quantity.

DESCRIPTION

       The  swap_lw_bytes  interface  performs a longword byte swap. The swap_word_bytes interface performs a short word byte swap. The swap_words
       interface performs a word byte swap. Many computer vendors support devices that use a big endian model of byte  ordering.  Because  Digital
       devices	support the little endian model of byte ordering, there is a need for these byte-swapping interfaces. In addition, some buses (for
       example, the VMEbus) can have specific or implied byte ordering that may require the use of these interfaces.

       Given that a longword is equal to 4 bytes; a short word is equal to 2 bytes; and 1 byte is equal to 8 bits, these interfaces swap bytes	as
       follows: The swap_lw_bytes interface takes the 32-bit quantity specified by the buffer argument and swaps all 4 bytes.  The swap_word_bytes
       interface takes the 32-bit quantity specified by the buffer argument and swaps the individual bytes that make up each word  of  the  32-bit
       quantity.  The swap_words interface takes the 32-bit quantity specified by the buffer argument and swaps the two 16-bit words.

       The following illustration compares the byte swapping performed by these interfaces.

			 31		  0
			  +---+---+---+---+ Starting value:    | a | b | c | d |
			  +---+---+---+---+

			  Long word byte swap
			  (swap_lw_bytes)

			 31		  0
			  +---+---+---+---+ Ending value:      | d | c | b | a |
			  +-------+---+---+

			  Short word byte swap
			  (swap_word_bytes)

			 31		  0
			  +---+---+---+---+ Ending value:      | b | a | d | c |
			  +---+---+---+---+

			 31		  0
			  +---+---+---+---+ Starting value:    |   ab  |   cd  |
			  +---+---+---+---+

			  Word byte swap
			  (swap_words)

			 31		  0
			  +---+---+---+---+ Ending value:      |  cd   |  ab   |
			  +---+---+---+---+

RETURN VALUES

       Upon successful completion, these interfaces return the swapped bytes.

																 swap_lw_bytes(9r)