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Diffstat (limited to 'newlib/libc/stdlib/div.c')
| -rw-r--r-- | newlib/libc/stdlib/div.c | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/newlib/libc/stdlib/div.c b/newlib/libc/stdlib/div.c new file mode 100644 index 00000000000..2c070dec71c --- /dev/null +++ b/newlib/libc/stdlib/div.c @@ -0,0 +1,132 @@ +/* +FUNCTION +<<div>>---divide two integers + +INDEX + div + +ANSI_SYNOPSIS + #include <stdlib.h> + div_t div(int <[n]>, int <[d]>); + +TRAD_SYNOPSIS + #include <stdlib.h> + div_t div(<[n]>, <[d]>) + int <[n]>, <[d]>; + +DESCRIPTION +Divide +@tex +$n/d$, +@end tex +@ifinfo +<[n]>/<[d]>, +@end ifinfo +returning quotient and remainder as two integers in a structure <<div_t>>. + +RETURNS +The result is represented with the structure + +. typedef struct +. { +. int quot; +. int rem; +. } div_t; + +where the <<quot>> field represents the quotient, and <<rem>> the +remainder. For nonzero <[d]>, if `<<<[r]> = div(<[n]>,<[d]>);>>' then +<[n]> equals `<<<[r]>.rem + <[d]>*<[r]>.quot>>'. + +To divide <<long>> rather than <<int>> values, use the similar +function <<ldiv>>. + +PORTABILITY +<<div>> is ANSI. + +No supporting OS subroutines are required. +*/ + +/* + * Copyright (c) 1990 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. + * 3. All advertising materials mentioning features or use of this software + * must display the following acknowledgement: + * This product includes software developed by the University of + * California, Berkeley and its contributors. + * 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. + */ + +#include <_ansi.h> +#include <stdlib.h> /* div_t */ + +div_t +_DEFUN (div, (num, denom), + int num _AND + int 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 or +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, but r.rem > 0, we also have the wrong answer. + * In this case, to get the right answer, subtract 1 from r.quot and + * add denom to r.rem. + */ + if (num >= 0 && r.rem < 0) { + ++r.quot; + r.rem -= denom; + } + else if (num < 0 && r.rem > 0) { + --r.quot; + r.rem += denom; + } + return (r); +} |