119 lines
2.6 KiB
C
119 lines
2.6 KiB
C
/*
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FUNCTION
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<<strncpy>>---counted copy string
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INDEX
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strncpy
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SYNOPSIS
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#include <string.h>
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char *strncpy(char *restrict <[dst]>, const char *restrict <[src]>,
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size_t <[length]>);
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DESCRIPTION
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<<strncpy>> copies not more than <[length]> characters from the
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the string pointed to by <[src]> (including the terminating
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null character) to the array pointed to by <[dst]>. If the
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string pointed to by <[src]> is shorter than <[length]>
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characters, null characters are appended to the destination
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array until a total of <[length]> characters have been
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written.
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RETURNS
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This function returns the initial value of <[dst]>.
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PORTABILITY
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<<strncpy>> is ANSI C.
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<<strncpy>> requires no supporting OS subroutines.
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QUICKREF
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strncpy ansi pure
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*/
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#include <string.h>
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#include <limits.h>
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/*SUPPRESS 560*/
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/*SUPPRESS 530*/
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/* Nonzero if either X or Y is not aligned on a "long" boundary. */
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#define UNALIGNED(X, Y) \
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(((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1)))
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#if LONG_MAX == 2147483647L
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#define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080)
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#else
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#if LONG_MAX == 9223372036854775807L
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/* Nonzero if X (a long int) contains a NULL byte. */
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#define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080)
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#else
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#error long int is not a 32bit or 64bit type.
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#endif
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#endif
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#ifndef DETECTNULL
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#error long int is not a 32bit or 64bit byte
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#endif
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#define TOO_SMALL(LEN) ((LEN) < sizeof (long))
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char *
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strncpy (char *__restrict dst0,
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const char *__restrict src0,
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size_t count)
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{
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#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
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char *dscan;
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const char *sscan;
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dscan = dst0;
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sscan = src0;
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while (count > 0)
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{
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--count;
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if ((*dscan++ = *sscan++) == '\0')
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break;
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}
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while (count-- > 0)
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*dscan++ = '\0';
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return dst0;
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#else
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char *dst = dst0;
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const char *src = src0;
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long *aligned_dst;
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const long *aligned_src;
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/* If SRC and DEST is aligned and count large enough, then copy words. */
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if (!UNALIGNED (src, dst) && !TOO_SMALL (count))
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{
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aligned_dst = (long*)dst;
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aligned_src = (long*)src;
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/* SRC and DEST are both "long int" aligned, try to do "long int"
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sized copies. */
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while (count >= sizeof (long int) && !DETECTNULL(*aligned_src))
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{
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count -= sizeof (long int);
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*aligned_dst++ = *aligned_src++;
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}
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dst = (char*)aligned_dst;
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src = (char*)aligned_src;
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}
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while (count > 0)
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{
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--count;
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if ((*dst++ = *src++) == '\0')
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break;
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}
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while (count-- > 0)
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*dst++ = '\0';
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return dst0;
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#endif /* not PREFER_SIZE_OVER_SPEED */
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}
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