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/*

FUNCTION

        <<strchr>>---search for character in string

INDEX

        strchr

ANSI_SYNOPSIS

        #include <string.h>

        char * strchr(const char *<[string]>, int <[c]>);

TRAD_SYNOPSIS

        #include <string.h>

        char * strchr(<[string]>, <[c]>);

        const char *<[string]>;

        int <[c]>;

DESCRIPTION

        This function finds the first occurence of <[c]> (converted to

        a char) in the string pointed to by <[string]> (including the

        terminating null character).

RETURNS

        Returns a pointer to the located character, or a null pointer

        if <[c]> does not occur in <[string]>.

PORTABILITY

<<strchr>> is ANSI C.

<<strchr>> requires no supporting OS subroutines.

QUICKREF

        strchr ansi pure

*/

#include <string.h>

#include <limits.h>

/* Nonzero if X is not aligned on a "long" boundary.  */

#define UNALIGNED(X) ((long)X & (sizeof (long) - 1))

/* How many bytes are loaded each iteration of the word copy loop.  */

#define LBLOCKSIZE (sizeof (long))

#if LONG_MAX == 2147483647L

#define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080)

#else

#if LONG_MAX == 9223372036854775807L

/* Nonzero if X (a long int) contains a NULL byte. */

#define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080)

#else

#error long int is not a 32bit or 64bit type.

#endif

#endif

/* DETECTCHAR returns nonzero if (long)X contains the byte used

   to fill (long)MASK. */

#define DETECTCHAR(X,MASK) (DETECTNULL(X ^ MASK))

char *

_DEFUN (strchr, (s1, i),

        _CONST char *s1 _AND

        int i)

{

  _CONST unsigned char *s = (_CONST unsigned char *)s1;

  unsigned char c = i;

#if !defined(PREFER_SIZE_OVER_SPEED) && !defined(__OPTIMIZE_SIZE__)

  unsigned long mask,j;

  unsigned long *aligned_addr;

  /* Special case for finding 0.  */

  if (!c)

    {

      while (UNALIGNED (s))

        {

          if (!*s)

            return (char *) s;

          s++;

        }

      /* Operate a word at a time.  */

      aligned_addr = (unsigned long *) s;

      while (!DETECTNULL (*aligned_addr))

        aligned_addr++;

      /* Found the end of string.  */

      s = (const unsigned char *) aligned_addr;

      while (*s)

        s++;

      return (char *) s;

    }

  /* All other bytes.  Align the pointer, then search a long at a time.  */

  while (UNALIGNED (s))

    {

      if (!*s)

        return NULL;

      if (*s == c)

        return (char *) s;

      s++;

    }

  mask = c;

  for (j = 8; j < LBLOCKSIZE * 8; j <<= 1)

    mask = (mask << j) | mask;

  aligned_addr = (unsigned long *) s;

  while (!DETECTNULL (*aligned_addr) && !DETECTCHAR (*aligned_addr, mask))

    aligned_addr++;

  /* The block of bytes currently pointed to by aligned_addr

     contains either a null or the target char, or both.  We

     catch it using the bytewise search.  */

  s = (unsigned char *) aligned_addr;

#endif /* not PREFER_SIZE_OVER_SPEED */

  while (*s && *s != c)

    s++;

  if (*s == c)

    return (char *)s;

  return NULL;

}