60 lines
1.7 KiB
C
60 lines
1.7 KiB
C
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/* buffer-lcm.c - compute a good buffer size for dealing with two files
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Copyright (C) 2002-2020 Free Software Foundation, Inc.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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/* Written by Paul Eggert. */
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#include <config.h>
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#include "buffer-lcm.h"
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/* Return a buffer size suitable for doing I/O with files whose block
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sizes are A and B. However, never return a value greater than
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LCM_MAX. */
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size_t
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buffer_lcm (size_t a, size_t b, size_t lcm_max)
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{
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size_t size;
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/* Use reasonable values if buffer sizes are zero. */
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if (!a)
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size = b ? b : 8 * 1024;
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else
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{
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if (b)
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{
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/* Return lcm (A, B) if it is in range; otherwise, fall back
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on A. */
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size_t lcm, m, n, q, r;
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/* N = gcd (A, B). */
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for (m = a, n = b; (r = m % n) != 0; m = n, n = r)
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continue;
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/* LCM = lcm (A, B), if in range. */
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q = a / n;
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lcm = q * b;
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if (lcm <= lcm_max && lcm / b == q)
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return lcm;
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}
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size = a;
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}
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return size <= lcm_max ? size : lcm_max;
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}
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