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/*
FUNCTION
<<memccpy>>---copy memory regions with end-token check
ANSI_SYNOPSIS
#include <string.h>
void* memccpy(void *<[out]>, const void *<[in]>,
int <[endchar]>, size_t <[n]>);
TRAD_SYNOPSIS
void *memccpy(<[out]>, <[in]>, <[endchar]>, <[n]>
void *<[out]>;
void *<[in]>;
int <[endchar]>;
size_t <[n]>;
DESCRIPTION
This function copies up to <[n]> bytes from the memory region
pointed to by <[in]> to the memory region pointed to by
<[out]>. If a byte matching the <[endchar]> is encountered,
the byte is copied and copying stops.
If the regions overlap, the behavior is undefined.
RETURNS
<<memccpy>> returns a pointer to the first byte following the
<[endchar]> in the <[out]> region. If no byte matching
<[endchar]> was copied, then <<NULL>> is returned.
PORTABILITY
<<memccpy>> is a GNU extension.
<<memccpy>> requires no supporting OS subroutines.
*/
#include <_ansi.h>
#include <stddef.h>
#include <string.h>
#include <limits.h>
/* Nonzero if either X or Y is not aligned on a "long" boundary. */
#define UNALIGNED(X, Y) \
(((long)X & (sizeof (long) - 1)) | ((long)Y & (sizeof (long) - 1)))
/* How many bytes are copied each iteration of the word copy loop. */
#define LITTLEBLOCKSIZE (sizeof (long))
/* Threshhold for punting to the byte copier. */
#define TOO_SMALL(LEN) ((LEN) < LITTLEBLOCKSIZE)
/* Macros for detecting endchar */
#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
_PTR
_DEFUN (memccpy, (dst0, src0, endchar, len0),
_PTR dst0 _AND
_CONST _PTR src0 _AND
int endchar0 _AND
size_t len0)
{
#if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__)
_PTR ptr = NULL;
char *dst = (char *) dst0;
char *src = (char *) src0;
char endchar = endchar0 & 0xff;
while (len0--)
{
if ((*dst++ = *src++) == endchar)
{
ptr = dst;
break;
}
}
return ptr;
#else
_PTR ptr = NULL;
char *dst = dst0;
_CONST char *src = src0;
long *aligned_dst;
_CONST long *aligned_src;
int len = len0;
char endchar = endchar0 & 0xff;
/* If the size is small, or either SRC or DST is unaligned,
then punt into the byte copy loop. This should be rare. */
if (!TOO_SMALL(len) && !UNALIGNED (src, dst))
{
int i;
unsigned long mask = 0;
aligned_dst = (long*)dst;
aligned_src = (long*)src;
/* The fast code reads the ASCII 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 NULL in the
result. */
for (i = 0; i < LITTLEBLOCKSIZE; i++)
mask = (mask << 8) + endchar;
/* Copy one long word at a time if possible. */
while (len >= LITTLEBLOCKSIZE)
{
unsigned long buffer = (unsigned long)(*aligned_src);
buffer ^= mask;
if (DETECTNULL (buffer))
break; /* endchar is found, go byte by byte from here */
*aligned_dst++ = *aligned_src++;
len -= LITTLEBLOCKSIZE;
}
/* Pick up any residual with a byte copier. */
dst = (char*)aligned_dst;
src = (char*)aligned_src;
}
while (len--)
{
if ((*dst++ = *src++) == endchar)
{
ptr = dst;
break;
}
}
return ptr;
#endif /* not PREFER_SIZE_OVER_SPEED */
}
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