mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-20 12:00:06 +00:00
84 lines
2.3 KiB
C
84 lines
2.3 KiB
C
|
/* memset -- set a block of memory to some byte value.
|
||
|
|
For Intel 80x86, x>=3.
|
||
|
|
Copyright (C) 1991, 1992, 1993 Free Software Foundation, Inc.
|
||
|
|
Contributed by Torbjorn Granlund (tege@sics.se).
|
||
|
|
|
||
|
|
The GNU C Library is free software; you can redistribute it and/or
|
||
|
|
modify it under the terms of the GNU Library General Public License as
|
||
|
|
published by the Free Software Foundation; either version 2 of the
|
||
|
|
License, or (at your option) any later version.
|
||
|
|
|
||
|
|
The GNU C Library is distributed in the hope that it will be useful,
|
||
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
||
|
|
Library General Public License for more details.
|
||
|
|
|
||
|
|
You should have received a copy of the GNU Library General Public
|
||
|
|
License along with the GNU C Library; see the file COPYING.LIB. If
|
||
|
|
not, write to the Free Software Foundation, Inc., 675 Mass Ave,
|
||
|
|
Cambridge, MA 02139, USA. */
|
||
|
|
|
||
|
|
#include <ansidecl.h>
|
||
|
|
#include <string.h>
|
||
|
|
#include <memcopy.h>
|
||
|
|
|
||
|
|
#ifdef __GNUC__
|
||
|
|
|
||
|
|
PTR
|
||
|
|
DEFUN(memset, (dstpp, c, len),
|
||
|
|
PTR dstpp AND int c AND size_t len)
|
||
|
|
{
|
||
|
|
unsigned long int dstp = (unsigned long int) dstpp;
|
||
|
|
|
||
|
|
/* This explicit register allocation
|
||
|
|
improves code very much indeed. */
|
||
|
|
register op_t x asm("ax");
|
||
|
|
|
||
|
|
x = (unsigned char) c;
|
||
|
|
|
||
|
|
/* Clear the direction flag, so filling will move forward. */
|
||
|
|
asm volatile("cld");
|
||
|
|
|
||
|
|
/* This threshold value is optimal. */
|
||
|
|
if (len >= 12)
|
||
|
|
{
|
||
|
|
/* Fill X with four copies of the char we want to fill with. */
|
||
|
|
x |= (x << 8);
|
||
|
|
x |= (x << 16);
|
||
|
|
|
||
|
|
/* Adjust LEN for the bytes handled in the first loop. */
|
||
|
|
len -= (-dstp) % OPSIZ;
|
||
|
|
|
||
|
|
/* There are at least some bytes to set.
|
||
|
|
No need to test for LEN == 0 in this alignment loop. */
|
||
|
|
|
||
|
|
/* Fill bytes until DSTP is aligned on a longword boundary. */
|
||
|
|
asm volatile("rep\n"
|
||
|
|
"stosb" /* %0, %2, %3 */ :
|
||
|
|
"=D" (dstp) :
|
||
|
|
"0" (dstp), "c" ((-dstp) % OPSIZ), "a" (x) :
|
||
|
|
"cx");
|
||
|
|
|
||
|
|
/* Fill longwords. */
|
||
|
|
asm volatile("rep\n"
|
||
|
|
"stosl" /* %0, %2, %3 */ :
|
||
|
|
"=D" (dstp) :
|
||
|
|
"0" (dstp), "c" (len / OPSIZ), "a" (x) :
|
||
|
|
"cx");
|
||
|
|
len %= OPSIZ;
|
||
|
|
}
|
||
|
|
|
||
|
|
/* Write the last few bytes. */
|
||
|
|
asm volatile("rep\n"
|
||
|
|
"stosb" /* %0, %2, %3 */ :
|
||
|
|
"=D" (dstp) :
|
||
|
|
"0" (dstp), "c" (len), "a" (x) :
|
||
|
|
"cx");
|
||
|
|
|
||
|
|
return dstpp;
|
||
|
|
}
|
||
|
|
|
||
|
|
#else
|
||
|
|
#include <sysdeps/generic/memset.c>
|
||
|
|
#endif
|