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71 theseven 1 
/*
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FUNCTION
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        <<memchr>>---search for character in memory
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INDEX
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        memchr
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ANSI_SYNOPSIS
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        #include <string.h>
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        void * memchr(const void *<[s1]>, int <[c]>, size_t <[n]>);
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TRAD_SYNOPSIS
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        #include <string.h>
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        void * memchr(<[s1]>, <[c]>, <[n]>);
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        void *<[string]>;
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        int *<[c]>;
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        size_t *<[n]>;
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DESCRIPTION
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        This function scans the first <[n]> bytes of the memory pointed
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        to by <[s1]> for the character <[c]> (converted to a char).
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RETURNS
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        Returns a pointer to the matching byte, or a null pointer if
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        <[c]> does not occur in <[s1]>.
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PORTABILITY
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<<memchr>> is ANSI C.
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<<memchr>> requires no supporting OS subroutines.
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QUICKREF
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        memchr ansi pure
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*/
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#include "global.h"
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#include "include/string.h"
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#include <limits.h>
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/* Nonzero if X is not aligned on a "long" boundary.  */
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#define UNALIGNED(X) ((long)X & (sizeof (long) - 1))
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/* How many bytes are loaded each iteration of the word copy loop.  */
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#define LBLOCKSIZE (sizeof (long))
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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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/* DETECTCHAR returns nonzero if (long)X contains the byte used
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   to fill (long)MASK. */
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#define DETECTCHAR(X,MASK) (DETECTNULL(X ^ MASK))
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void *
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_DEFUN (memchr, (s1, i, n),
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        _CONST void *s1 _AND
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        int i _AND size_t n)
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{
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  _CONST unsigned char *s = (_CONST unsigned char *)s1;
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#if defined(PREFER_SIZE_OVER_SPEED)
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  unsigned char c = (unsigned char)i;
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  while (n-- > 0)
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    {
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      if (*s == c)
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        {
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          return (void *)s;
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        }
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      s++;
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    }
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  return NULL;
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#else
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  unsigned char c = (unsigned char)i;
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  unsigned long mask,j;
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  unsigned long *aligned_addr;
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  if (!UNALIGNED (s))
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    {
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      mask = 0;
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      for (j = 0; j < LBLOCKSIZE; j++)
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        mask = (mask << 8) | c;
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      aligned_addr = (unsigned long*)s;
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      while ((!DETECTCHAR (*aligned_addr, mask)) && (n>LBLOCKSIZE))
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        {
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          aligned_addr++;
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          n -= LBLOCKSIZE;
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        }
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      /* The block of bytes currently pointed to by aligned_addr
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         may contain the target character or there may be less than
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         LBLOCKSIZE bytes left to search. We check the last few
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         bytes using the bytewise search.  */
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      s = (unsigned char*)aligned_addr;
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    }
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  while (n-- > 0)
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    {
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      if (*s == c)
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        {
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          return (void *)s;
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        }
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      s++;
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    }
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  return NULL;
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#endif /* not PREFER_SIZE_OVER_SPEED */
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}