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45 lines
900 B
C
45 lines
900 B
C
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/*
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FUNCTION
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<<swab>>---swap adjacent bytes
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ANSI_SYNOPSIS
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#include <unistd.h>
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void swab(const void *<[in]>, void *<[out]>, ssize_t <[n]>);
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TRAD_SYNOPSIS
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void swab(<[in]>, <[out]>, <[n]>
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void *<[in]>;
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void *<[out]>;
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ssize_t <[n]>;
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DESCRIPTION
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This function copies <[n]> bytes from the memory region
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pointed to by <[in]> to the memory region pointed to by
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<[out]>, exchanging adjacent even and odd bytes.
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PORTABILITY
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<<swab>> requires no supporting OS subroutines.
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*/
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#include <unistd.h>
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void
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_DEFUN (swab, (b1, b2, length),
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_CONST void *b1 _AND
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void *b2 _AND
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ssize_t length)
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{
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const char *from = b1;
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char *to = b2;
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ssize_t ptr;
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for (ptr = 1; ptr < length; ptr += 2)
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{
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char p = from[ptr];
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char q = from[ptr-1];
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to[ptr-1] = p;
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to[ptr ] = q;
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}
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if (ptr == length) /* I.e., if length is odd, */
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to[ptr-1] = 0; /* then pad with a NUL. */
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}
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