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Diffstat (limited to 'lib/libc/stdlib/div.c')
-rw-r--r-- | lib/libc/stdlib/div.c | 77 |
1 files changed, 77 insertions, 0 deletions
diff --git a/lib/libc/stdlib/div.c b/lib/libc/stdlib/div.c new file mode 100644 index 0000000..ef93d73 --- /dev/null +++ b/lib/libc/stdlib/div.c @@ -0,0 +1,77 @@ +/* + * Copyright (c) 1990, 1993 + * The Regents of the University of California. All rights reserved. + * + * This code is derived from software contributed to Berkeley by + * Chris Torek. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * 4. Neither the name of the University nor the names of its contributors + * may be used to endorse or promote products derived from this software + * without specific prior written permission. + * + * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND + * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE + * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL + * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS + * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) + * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT + * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY + * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF + * SUCH DAMAGE. + */ + +#if defined(LIBC_SCCS) && !defined(lint) +static char sccsid[] = "@(#)div.c 8.1 (Berkeley) 6/4/93"; +#endif /* LIBC_SCCS and not lint */ +#include <sys/cdefs.h> +__FBSDID("$FreeBSD$"); + +#include <stdlib.h> /* div_t */ + +div_t +div(num, denom) + int num, denom; +{ + div_t r; + + r.quot = num / denom; + r.rem = num % denom; + /* + * The ANSI standard says that |r.quot| <= |n/d|, where + * n/d is to be computed in infinite precision. In other + * words, we should always truncate the quotient towards + * 0, never -infinity. + * + * Machine division and remainer may work either way when + * one or both of n or d is negative. If only one is + * negative and r.quot has been truncated towards -inf, + * r.rem will have the same sign as denom and the opposite + * sign of num; if both are negative and r.quot has been + * truncated towards -inf, r.rem will be positive (will + * have the opposite sign of num). These are considered + * `wrong'. + * + * If both are num and denom are positive, r will always + * be positive. + * + * This all boils down to: + * if num >= 0, but r.rem < 0, we got the wrong answer. + * In that case, to get the right answer, add 1 to r.quot and + * subtract denom from r.rem. + */ + if (num >= 0 && r.rem < 0) { + r.quot++; + r.rem -= denom; + } + return (r); +} |