From 325619eb0d823301dff877ecf7db896d9f17bd03 Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Thu, 24 Nov 2005 06:48:03 +0000 Subject: Initial version, from diffutils --- lib/buffer-lcm.c | 59 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 59 insertions(+) create mode 100644 lib/buffer-lcm.c (limited to 'lib') diff --git a/lib/buffer-lcm.c b/lib/buffer-lcm.c new file mode 100644 index 000000000..c3f610943 --- /dev/null +++ b/lib/buffer-lcm.c @@ -0,0 +1,59 @@ +/* buffer-lcm.c - compute a good buffer size for dealing with two files + + Copyright (C) 2002, 2005 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 2, 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, write to the Free Software Foundation, + Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ + +/* 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; +} -- cgit v1.2.3-70-g09d2