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/* Buffer primitives for comparison operations.
Copyright (C) 1993, 1995, 1998, 2001-2002, 2006, 2009-2013, 2015-2023 Free
Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#include <config.h>
#include <errno.h>
#include <limits.h>
#include <signal.h>
#include <unistd.h>
#include <stdint.h>
#include <inttypes.h>
#include <sys/types.h>
#include "cmpbuf.h"
#include "intprops.h"
#ifndef SSIZE_MAX
# define SSIZE_MAX TYPE_MAXIMUM (ssize_t)
#endif
#undef MIN
#define MIN(a, b) ((a) <= (b) ? (a) : (b))
/* Read NBYTES bytes from descriptor FD into BUF.
NBYTES must not be SIZE_MAX.
Return the number of characters successfully read.
On error, return SIZE_MAX, setting errno.
The number returned is always NBYTES unless end-of-file or error. */
size_t
block_read (int fd, char *buf, size_t nbytes)
{
char *bp = buf;
char const *buflim = buf + nbytes;
size_t readlim = MIN (SSIZE_MAX, SIZE_MAX);
do
{
size_t bytes_remaining = buflim - bp;
size_t bytes_to_read = MIN (bytes_remaining, readlim);
ssize_t nread = read (fd, bp, bytes_to_read);
if (nread <= 0)
{
if (nread == 0)
break;
/* Accommodate Tru64 5.1, which can't read more than INT_MAX
bytes at a time. They call that a 64-bit OS? */
if (errno == EINVAL && INT_MAX < bytes_to_read)
{
readlim = INT_MAX;
continue;
}
/* This is needed for programs that have signal handlers on
older hosts without SA_RESTART. It also accommodates
ancient AIX hosts that set errno to EINTR after uncaught
SIGCONT. See <news:1r77ojINN85n@ftp.UU.NET>
(1993-04-22). */
if (! SA_RESTART && errno == EINTR)
continue;
return SIZE_MAX;
}
bp += nread;
}
while (bp < buflim);
return bp - buf;
}
/* Least common multiple of two buffer sizes A and B. However, if
either A or B is zero, or if the multiple is greater than LCM_MAX,
return a reasonable buffer size. */
size_t
buffer_lcm (size_t a, size_t b, size_t lcm_max)
{
size_t lcm, m, n, q, r;
/* Yield reasonable values if buffer sizes are zero. */
if (!a)
return b ? b : 8 * 1024;
if (!b)
return a;
/* n = gcd (a, b) */
for (m = a, n = b; (r = m % n) != 0; m = n, n = r)
continue;
/* Yield a if there is an overflow. */
q = a / n;
return !INT_MULTIPLY_WRAPV (q, b, &lcm) && lcm <= lcm_max ? lcm : a;
}
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