118 lines
2.7 KiB
C
118 lines
2.7 KiB
C
/*
|
|
FUNCTION
|
|
<<memchr>>---search for character in memory
|
|
|
|
INDEX
|
|
memchr
|
|
|
|
ANSI_SYNOPSIS
|
|
#include <string.h>
|
|
void * memchr(const void *<[s1]>, int <[c]>, size_t <[n]>);
|
|
|
|
TRAD_SYNOPSIS
|
|
#include <string.h>
|
|
void * memchr(<[s1]>, <[c]>, <[n]>);
|
|
void *<[string]>;
|
|
int *<[c]>;
|
|
size_t *<[n]>;
|
|
|
|
DESCRIPTION
|
|
This function scans the first <[n]> bytes of the memory pointed
|
|
to by <[s1]> for the character <[c]> (converted to a char).
|
|
|
|
RETURNS
|
|
Returns a pointer to the matching byte, or a null pointer if
|
|
<[c]> does not occur in <[s1]>.
|
|
|
|
PORTABILITY
|
|
<<memchr>> is ANSI C.
|
|
|
|
<<memchr>> requires no supporting OS subroutines.
|
|
|
|
QUICKREF
|
|
memchr ansi pure
|
|
*/
|
|
|
|
#include <string.h>
|
|
#include <limits.h>
|
|
#include "_ansi.h" /* for _DEFUN */
|
|
|
|
/* Nonzero if X is not aligned on a "long" boundary. */
|
|
#define ROCKBOX_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))
|
|
|
|
void *
|
|
_DEFUN (memchr, (s1, i, n),
|
|
_CONST void *s1 _AND
|
|
int i _AND size_t n)
|
|
{
|
|
_CONST unsigned char *s = (_CONST unsigned char *)s1;
|
|
#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
|
|
unsigned char c = (unsigned char)i;
|
|
|
|
while (n-- > 0)
|
|
{
|
|
if (*s == c)
|
|
{
|
|
return (void *)s;
|
|
}
|
|
s++;
|
|
}
|
|
|
|
return NULL;
|
|
#else
|
|
unsigned char c = (unsigned char)i;
|
|
unsigned long mask,j;
|
|
unsigned long *aligned_addr;
|
|
|
|
if (!ROCKBOX_UNALIGNED (s))
|
|
{
|
|
mask = 0;
|
|
for (j = 0; j < LBLOCKSIZE; j++)
|
|
mask = (mask << 8) | c;
|
|
|
|
aligned_addr = (unsigned long*)s;
|
|
while ((!DETECTCHAR (*aligned_addr, mask)) && (n>LBLOCKSIZE))
|
|
{
|
|
aligned_addr++;
|
|
n -= LBLOCKSIZE;
|
|
}
|
|
|
|
/* The block of bytes currently pointed to by aligned_addr
|
|
may contain the target character or there may be less than
|
|
LBLOCKSIZE bytes left to search. We check the last few
|
|
bytes using the bytewise search. */
|
|
|
|
s = (unsigned char*)aligned_addr;
|
|
}
|
|
|
|
while (n-- > 0)
|
|
{
|
|
if (*s == c)
|
|
{
|
|
return (void *)s;
|
|
}
|
|
s++;
|
|
}
|
|
|
|
return NULL;
|
|
#endif /* not PREFER_SIZE_OVER_SPEED */
|
|
}
|