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1 /* |
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2 * Copyright (c) 1990, 1993 |
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3 * The Regents of the University of California. All rights reserved. |
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4 * |
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5 * This code is derived from software contributed to Berkeley by |
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6 * Chris Torek. |
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7 * |
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8 * Redistribution and use in source and binary forms, with or without |
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9 * modification, are permitted provided that the following conditions |
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10 * are met: |
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11 * 1. Redistributions of source code must retain the above copyright |
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12 * notice, this list of conditions and the following disclaimer. |
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13 * 2. Redistributions in binary form must reproduce the above copyright |
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14 * notice, this list of conditions and the following disclaimer in the |
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15 * documentation and/or other materials provided with the distribution. |
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16 * 4. Neither the name of the University nor the names of its contributors |
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17 * may be used to endorse or promote products derived from this software |
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18 * without specific prior written permission. |
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19 * |
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20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
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21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
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22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
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24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
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25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
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26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
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27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
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29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
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30 * SUCH DAMAGE. |
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31 * © Portions copyright (c) 2005-2006 Nokia Corporation. All rights reserved. |
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32 */ |
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33 |
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34 #if defined(LIBC_SCCS) && !defined(lint) |
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35 static char sccsid[] = "@(#)div.c 8.1 (Berkeley) 6/4/93"; |
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36 #endif /* LIBC_SCCS and not lint */ |
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37 #include <sys/cdefs.h> |
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38 __FBSDID("$FreeBSD: src/lib/libc/stdlib/div.c,v 1.2 2002/03/22 21:53:10 obrien Exp $"); |
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39 |
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40 #include <stdlib.h> /* div_t */ |
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41 |
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42 EXPORT_C |
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43 div_t |
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44 div(num, denom) |
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45 int num, denom; |
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46 { |
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47 div_t r; |
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48 |
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49 r.quot = num / denom; |
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50 r.rem = num % denom; |
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51 /* |
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52 * The ANSI standard says that |r.quot| <= |n/d|, where |
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53 * n/d is to be computed in infinite precision. In other |
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54 * words, we should always truncate the quotient towards |
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55 * 0, never -infinity. |
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56 * |
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57 * Machine division and remainer may work either way when |
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58 * one or both of n or d is negative. If only one is |
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59 * negative and r.quot has been truncated towards -inf, |
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60 * r.rem will have the same sign as denom and the opposite |
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61 * sign of num; if both are negative and r.quot has been |
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62 * truncated towards -inf, r.rem will be positive (will |
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63 * have the opposite sign of num). These are considered |
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64 * `wrong'. |
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65 * |
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66 * If both are num and denom are positive, r will always |
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67 * be positive. |
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68 * |
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69 * This all boils down to: |
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70 * if num >= 0, but r.rem < 0, we got the wrong answer. |
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71 * In that case, to get the right answer, add 1 to r.quot and |
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72 * subtract denom from r.rem. |
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73 */ |
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74 if (num >= 0 && r.rem < 0) { |
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75 r.quot++; |
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76 r.rem -= denom; |
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77 } |
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78 return (r); |
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79 } |