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/* buffer-lcm.c - compute a good buffer size for dealing with two files
Copyright (C) 2002-2020 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 <https://www.gnu.org/licenses/>. */
/* Written by Paul Eggert. */
#include <config.h>
#include "buffer-lcm.h"
/* Return a buffer size suitable for doing I/O with files whose block
sizes are A and B. However, never return a value greater than
LCM_MAX. */
size_t
buffer_lcm (size_t a, size_t b, size_t lcm_max)
{
size_t size;
/* Use reasonable values if buffer sizes are zero. */
if (!a)
size = b ? b : 8 * 1024;
else
{
if (b)
{
/* Return lcm (A, B) if it is in range; otherwise, fall back
on A. */
size_t lcm, m, n, q, r;
/* N = gcd (A, B). */
for (m = a, n = b; (r = m % n) != 0; m = n, n = r)
continue;
/* LCM = lcm (A, B), if in range. */
q = a / n;
lcm = q * b;
if (lcm <= lcm_max && lcm / b == q)
return lcm;
}
size = a;
}
return size <= lcm_max ? size : lcm_max;
}
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