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1 //=========================================================================== |
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2 // |
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3 // div.cxx |
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4 // |
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5 // Real alternative for inline implementation of the ANSI standard |
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6 // div() utility function defined in section 7.10.6.2 of the standard |
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7 // |
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8 //=========================================================================== |
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9 //####COPYRIGHTBEGIN#### |
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10 // |
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11 // ------------------------------------------- |
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12 // The contents of this file are subject to the Cygnus eCos Public License |
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13 // Version 1.0 (the "License"); you may not use this file except in |
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14 // compliance with the License. You may obtain a copy of the License at |
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15 // http://sourceware.cygnus.com/ecos |
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16 // |
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17 // Software distributed under the License is distributed on an "AS IS" |
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18 // basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the |
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19 // License for the specific language governing rights and limitations under |
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20 // the License. |
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21 // |
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22 // The Original Code is eCos - Embedded Cygnus Operating System, released |
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23 // September 30, 1998. |
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24 // |
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25 // The Initial Developer of the Original Code is Cygnus. Portions created |
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26 // by Cygnus are Copyright (C) 1998 Cygnus Solutions. All Rights Reserved. |
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27 // ------------------------------------------- |
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28 // |
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29 //####COPYRIGHTEND#### |
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30 //=========================================================================== |
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31 //#####DESCRIPTIONBEGIN#### |
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32 // |
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33 // Author(s): jlarmour |
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34 // Contributors: jlarmour@cygnus.co.uk |
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35 // Date: 1998-02-13 |
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36 // Purpose: |
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37 // Description: |
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38 // Usage: |
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39 // |
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40 //####DESCRIPTIONEND#### |
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41 // |
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42 //=========================================================================== |
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43 // |
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44 // This code is based on code with the following copyright: |
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45 // |
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46 /* |
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47 * Copyright (c) 1990 Regents of the University of California. |
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48 * All rights reserved. |
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49 * |
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50 * This code is derived from software contributed to Berkeley by |
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51 * Chris Torek. |
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52 * |
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53 * Redistribution and use in source and binary forms, with or without |
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54 * modification, are permitted provided that the following conditions |
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55 * are met: |
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56 * 1. Redistributions of source code must retain the above copyright |
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57 * notice, this list of conditions and the following disclaimer. |
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58 * 2. Redistributions in binary form must reproduce the above copyright |
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59 * notice, this list of conditions and the following disclaimer in the |
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60 * documentation and/or other materials provided with the distribution. |
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61 * 3. All advertising materials mentioning features or use of this software |
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62 * must display the following acknowledgement: |
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63 * This product includes software developed by the University of |
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64 * California, Berkeley and its contributors. |
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65 * 4. Neither the name of the University nor the names of its contributors |
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66 * may be used to endorse or promote products derived from this software |
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67 * without specific prior written permission. |
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68 * |
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69 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND |
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70 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
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71 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
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72 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE |
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73 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL |
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74 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS |
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75 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
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76 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT |
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77 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY |
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78 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF |
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79 * SUCH DAMAGE. |
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80 */ |
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81 |
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82 |
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83 // CONFIGURATION |
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84 |
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85 #include <pkgconf/libc.h> // Configuration header |
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86 |
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87 // Include the C library? |
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88 #ifdef CYGPKG_LIBC |
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89 |
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90 // INCLUDES |
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91 |
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92 #include <cyg/infra/cyg_type.h> // Common type definitions and support |
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93 #include <cyg/infra/cyg_trac.h> // Tracing support |
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94 |
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95 // We don't want the inline versions of stdlib functions defined here |
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96 |
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97 #ifdef CYGIMP_LIBC_STDLIB_INLINES |
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98 #undef CYGIMP_LIBC_STDLIB_INLINES |
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99 #endif |
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100 |
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101 #include <stddef.h> // NULL, wchar_t and size_t from compiler |
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102 #include <stdlib.h> // Main header for stdlib functions |
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103 #include "clibincl/stdlibsupp.hxx" // Support for stdlib functions |
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104 |
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105 |
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106 // EXPORTED SYMBOLS |
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107 |
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108 externC div_t |
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109 div( int numer, int denom ) CYGPRI_LIBC_WEAK_ALIAS("_div"); |
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110 |
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111 |
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112 // FUNCTIONS |
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113 |
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114 div_t |
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115 _div( int numer, int denom ) |
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116 { |
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117 div_t result; |
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118 |
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119 CYG_REPORT_FUNCNAMETYPE( "_div", "quotient: %d"); |
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120 CYG_REPORT_FUNCARG2DV( numer, denom ); |
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121 |
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122 // The ANSI standard says that |r.quot| <= |n/d|, where |
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123 // n/d is to be computed in infinite precision. In other |
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124 // words, we should always truncate the quotient towards |
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125 // 0, never -infinity. |
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126 // |
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127 // Machine division and remainer may work either way when |
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128 // one or both of n or d is negative. If only one is |
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129 // negative and r.quot has been truncated towards -inf, |
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130 // r.rem will have the same sign as denom and the opposite |
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131 // sign of num; if both are negative and r.quot has been |
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132 // truncated towards -inf, r.rem will be positive (will |
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133 // have the opposite sign of num). These are considered |
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134 // `wrong'. |
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135 // |
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136 // If both are num and denom are positive, r will always |
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137 // be positive. |
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138 // |
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139 // This all boils down to: |
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140 // if num >= 0, but r.rem < 0, we got the wrong answer. |
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141 // In that case, to get the right answer, add 1 to r.quot and |
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142 // subtract denom from r.rem. |
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143 |
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144 result.quot = numer / denom; |
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145 result.rem = numer % denom; |
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146 |
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147 if ( (numer >= 0) && (result.rem < 0) ) |
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148 { |
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149 result.quot++; |
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150 result.rem -= denom; |
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151 } // if |
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152 |
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153 CYG_REPORT_RETVAL( result.quot ); |
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154 |
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155 return result; |
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156 } // _div() |
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157 |
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158 #endif // ifdef CYGPKG_LIBC |
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159 |
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160 // EOF div.cxx |
