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/*

FUNCTION

        <<swab>>---swap adjacent bytes

ANSI_SYNOPSIS

        #include <unistd.h>

        void swab(const void *<[in]>, void *<[out]>, ssize_t <[n]>);

TRAD_SYNOPSIS

        void swab(<[in]>, <[out]>, <[n]>

        void *<[in]>;

        void *<[out]>;

        ssize_t <[n]>;

DESCRIPTION

        This function copies <[n]> bytes from the memory region

        pointed to by <[in]> to the memory region pointed to by

        <[out]>, exchanging adjacent even and odd bytes.

PORTABILITY

<<swab>> requires no supporting OS subroutines.

*/

#include <unistd.h>

void

_DEFUN (swab, (b1, b2, length),

        _CONST void *b1 _AND

        void *b2 _AND

        ssize_t length)

{

  const char *from = b1;

  char *to = b2;

  ssize_t ptr;

  for (ptr = 1; ptr < length; ptr += 2)

    {

      char p = from[ptr];

      char q = from[ptr-1];

      to[ptr-1] = p;

      to[ptr  ] = q;

    }

  if (ptr == length) /* I.e., if length is odd, */

    to[ptr-1] = 0;   /* then pad with a NUL. */

}