/* $OpenBSD: div.c,v 1.5 2005/08/08 08:05:36 espie Exp $ */ | |

/* | |

* 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. 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 <stdlib.h> /* div_t */ | |

div_t | |

div(int num, 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. | |

* | |

* 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); | |

} |