diff options
Diffstat (limited to 'gl/lib/buffer-lcm.c')
-rw-r--r-- | gl/lib/buffer-lcm.c | 59 |
1 files changed, 59 insertions, 0 deletions
diff --git a/gl/lib/buffer-lcm.c b/gl/lib/buffer-lcm.c new file mode 100644 index 000000000..1d22dac7d --- /dev/null +++ b/gl/lib/buffer-lcm.c @@ -0,0 +1,59 @@ +/* buffer-lcm.c - compute a good buffer size for dealing with two files + + Copyright (C) 2002-2012 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 <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; +} |