/* buffer-lcm.c - compute a good buffer size for dealing with two files Copyright (C) 2002, 2005, 2009 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/>. */ /* Written by Paul Eggert. */ #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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