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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
  buffer
      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.

Index for Section 9r

Alphabetical listing for S

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