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Pull up following revision(s) (requested by jdolecek in ticket #1198): 

lib/libc/stdio/fread.c: revision 1.24 (via patch)

for unbuffered I/O arrange for the destination buffer to be filled in one
go, instead of triggering long series of 1 byte read(2)s; this speeds up
fread() several order of magnitudes for this case, directly proportional
to the size of the supplied buffer
change adapted from OpenBSD rev. 1.19

fixes PR lib/55808 by Roland Illig
This commit is contained in:
martin 2021-02-07 17:41:02 +00:00
parent df5ad49ea1
commit bbb138e1ad
1 changed files with 32 additions and 2 deletions
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34
lib/libc/stdio/fread.c
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@ -1,4 +1,4 @@
/* $NetBSD: fread.c,v 1.22 2012/03/15 18:22:30 christos Exp $ */
/* $NetBSD: fread.c,v 1.22.34.1 2021/02/07 17:41:02 martin Exp $ */
/*-
* Copyright (c) 1990, 1993
@ -37,7 +37,7 @@
#if 0
static char sccsid[] = "@(#)fread.c 8.2 (Berkeley) 12/11/93";
#else
__RCSID("$NetBSD: fread.c,v 1.22 2012/03/15 18:22:30 christos Exp $");
__RCSID("$NetBSD: fread.c,v 1.22.34.1 2021/02/07 17:41:02 martin Exp $");
#endif
#endif /* LIBC_SCCS and not lint */
@ -72,6 +72,36 @@ fread(void *buf, size_t size, size_t count, FILE *fp)
fp->_r = 0;
total = resid;
p = buf;
/*
* If we're unbuffered we know that the buffer in fp is empty so
* we can read directly into buf. This is much faster than a
* series of one byte reads into fp->_nbuf.
*/
if ((fp->_flags & __SNBF) != 0) {
while (resid > 0) {
/* set up the buffer */
fp->_bf._base = fp->_p = (unsigned char *)p;
fp->_bf._size = resid;
if (__srefill(fp)) {
/* no more input: return partial result */
count = (total - resid) / size;
break;
}
p += fp->_r;
resid -= fp->_r;
}
/* restore the old buffer (see __smakebuf) */
fp->_bf._base = fp->_p = fp->_nbuf;
fp->_bf._size = 1;
fp->_r = 0;
FUNLOCKFILE(fp);
return (count);
}
while (resid > (size_t)(r = fp->_r)) {
(void)memcpy(p, fp->_p, (size_t)r);
fp->_p += r;