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/*
FUNCTION
<<rawmemchr>>---find character in memory
INDEX
rawmemchr
SYNOPSIS
#include <string.h>
void *rawmemchr(const void *<[src]>, int <[c]>);
DESCRIPTION
This function searches memory starting at <<*<[src]>>> for the
character <[c]>. The search only ends with the first occurrence
of <[c]>; in particular, <<NUL>> does not terminate the search.
No bounds checking is performed, so this function should only
be used when it is certain that the character <[c]> will be found.
RETURNS
A pointer to the first occurance of character <[c]>.
PORTABILITY
<<rawmemchr>> is a GNU extension.
<<rawmemchr>> requires no supporting OS subroutines.
QUICKREF
rawmemchr
*/
#include <_ansi.h>
#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))
/* Threshhold for punting to the bytewise iterator. */
#define TOO_SMALL(LEN) ((LEN) < LBLOCKSIZE)
#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
#ifndef DETECTNULL
#error long int is not a 32bit or 64bit byte
#endif
/* DETECTCHAR returns nonzero if (long)X contains the byte used
to fill (long)MASK. */
#define DETECTCHAR(X,MASK) (DETECTNULL(X ^ MASK))
void *
rawmemchr (const void *src_void,
int c)
{
const unsigned char *src = (const unsigned char *) src_void;
unsigned char d = c;
#if !defined(PREFER_SIZE_OVER_SPEED) && !defined(__OPTIMIZE_SIZE__)
unsigned long *asrc;
unsigned long mask;
unsigned int i;
while (UNALIGNED (src))
{
if (*src == d)
return (void *) src;
src++;
}
/* If we get this far, we know that src is word-aligned. */
/* The fast code reads the source one word at a time and only
performs the bytewise search on word-sized segments if they
contain the search character, which is detected by XORing
the word-sized segment with a word-sized block of the search
character and then detecting for the presence of NUL in the
result. */
asrc = (unsigned long *) src;
mask = d << 8 | d;
mask = mask << 16 | mask;
for (i = 32; i < LBLOCKSIZE * 8; i <<= 1)
mask = (mask << i) | mask;
while (1)
{
if (DETECTCHAR (*asrc, mask))
break;
asrc++;
}
/* We have the matching word, now we resort to a bytewise loop. */
src = (unsigned char *) asrc;
#endif /* !PREFER_SIZE_OVER_SPEED && !__OPTIMIZE_SIZE__ */
while (1)
{
if (*src == d)
return (void *) src;
src++;
}
}
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