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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.17.0/] [newlib/] [libc/] [string/] [memchr.c] - Blame information for rev 158

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1 148 jeremybenn
/*
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FUNCTION
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        <<memchr>>---find 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 *<[src]>, int <[c]>, size_t <[length]>);
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TRAD_SYNOPSIS
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        #include <string.h>
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        void *memchr(<[src]>, <[c]>, <[length]>)
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        void *<[src]>;
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        void *<[c]>;
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        size_t <[length]>;
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DESCRIPTION
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        This function searches memory starting at <<*<[src]>>> for the
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        character <[c]>.  The search only ends with the first
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        occurrence of <[c]>, or after <[length]> characters; in
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        particular, <<NUL>> does not terminate the search.
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RETURNS
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        If the character <[c]> is found within <[length]> characters
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        of <<*<[src]>>>, a pointer to the character is returned. If
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        <[c]> is not found, then <<NULL>> is returned.
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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 <_ansi.h>
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#include <string.h>
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#include <limits.h>
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/* Nonzero if either X or Y 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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/* Threshhold for punting to the bytewise iterator.  */
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#define TOO_SMALL(LEN)  ((LEN) < LBLOCKSIZE)
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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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/* 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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_PTR
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_DEFUN (memchr, (src_void, c, length),
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        _CONST _PTR src_void _AND
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        int c _AND
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        size_t length)
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{
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  _CONST unsigned char *src = (_CONST unsigned char *) src_void;
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  unsigned char d = c;
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#if !defined(PREFER_SIZE_OVER_SPEED) && !defined(__OPTIMIZE_SIZE__)
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  unsigned long *asrc;
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  unsigned long  mask;
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  int i;
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  while (UNALIGNED (src))
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    {
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      if (!length--)
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        return NULL;
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      if (*src == d)
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        return (void *) src;
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      src++;
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    }
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  if (!TOO_SMALL (length))
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    {
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      /* If we get this far, we know that length is large and src is
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         word-aligned. */
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      /* The fast code reads the source one word at a time and only
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         performs the bytewise search on word-sized segments if they
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         contain the search character, which is detected by XORing
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         the word-sized segment with a word-sized block of the search
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         character and then detecting for the presence of NUL in the
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         result.  */
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      asrc = (unsigned long *) src;
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      mask = d << 8 | d;
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      mask = mask << 16 | mask;
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      for (i = 32; i < LBLOCKSIZE * 8; i <<= 1)
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        mask = (mask << i) | mask;
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      while (length >= LBLOCKSIZE)
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        {
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          if (DETECTCHAR (*asrc, mask))
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            break;
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          length -= LBLOCKSIZE;
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          asrc++;
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        }
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      /* If there are fewer than LBLOCKSIZE characters left,
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         then we resort to the bytewise loop.  */
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      src = (unsigned char *) asrc;
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    }
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#endif /* not PREFER_SIZE_OVER_SPEED */
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  while (length--)
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    {
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      if (*src == d)
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        return (void *) src;
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      src++;
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    }
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  return NULL;
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}

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