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/*
FUNCTION
<<strchr>>---search for character in string
INDEX
strchr
SYNOPSIS
#include <string.h>
char * strchr(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 *
strchr (const char *s1,
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;
}
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