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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 // ISO C implementation for div() utility function |
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6 // |
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7 //=========================================================================== |
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8 //####COPYRIGHTBEGIN#### |
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9 // |
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10 // ------------------------------------------- |
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11 // The contents of this file are subject to the Cygnus eCos Public License |
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12 // Version 1.0 (the "License"); you may not use this file except in |
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13 // compliance with the License. You may obtain a copy of the License at |
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14 // http://sourceware.cygnus.com/ecos |
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15 // |
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16 // Software distributed under the License is distributed on an "AS IS" |
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17 // basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the |
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18 // License for the specific language governing rights and limitations under |
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19 // the License. |
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20 // |
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21 // The Original Code is eCos - Embedded Cygnus Operating System, released |
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22 // September 30, 1998. |
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23 // |
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24 // The Initial Developer of the Original Code is Cygnus. Portions created |
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25 // by Cygnus are Copyright (C) 1998,1999 Cygnus Solutions. All Rights Reserved. |
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26 // ------------------------------------------- |
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27 // |
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28 //####COPYRIGHTEND#### |
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29 //=========================================================================== |
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30 //#####DESCRIPTIONBEGIN#### |
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31 // |
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32 // Author(s): jlarmour |
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33 // Contributors: jlarmour |
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34 // Date: 1999-03-02 |
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35 // Purpose: Provide implementation of div() from ISO C section 7.10.6.2 |
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36 // Description: |
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37 // Usage: |
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38 // |
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39 //####DESCRIPTIONEND#### |
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40 // |
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41 //=========================================================================== |
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42 // |
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43 |
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44 // CONFIGURATION |
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45 |
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46 #include <pkgconf/libc.h> // Configuration header |
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47 |
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48 // INCLUDES |
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49 |
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50 #include <cyg/infra/cyg_type.h> // Common type definitions and support |
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51 #include <cyg/infra/cyg_ass.h> // Assertion support |
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52 #include <cyg/infra/cyg_trac.h> // Tracing support |
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53 |
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54 // We don't want the inline versions of stdlib functions defined here |
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55 |
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56 #ifdef CYGIMP_LIBC_STDLIB_INLINES |
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57 # undef CYGIMP_LIBC_STDLIB_INLINES |
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58 #endif |
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59 |
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60 #include <stddef.h> // NULL, wchar_t and size_t from compiler |
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61 #include <stdlib.h> // Main header for stdlib functions |
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62 |
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63 |
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64 // FUNCTIONS |
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65 |
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66 externC div_t |
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67 __div( int __numer, int __denom ) |
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68 { |
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69 div_t __ret; |
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70 |
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71 CYG_REPORT_FUNCNAMETYPE( "__div", "quotient: %d"); |
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72 CYG_REPORT_FUNCARG2DV( __numer, __denom ); |
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73 // FIXME: what if they want it handled with SIGFPE? Should have option |
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74 CYG_PRECONDITION(__denom != 0, "division by zero attempted!"); |
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75 |
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76 __ret.quot = __numer / __denom; |
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77 __ret.rem = __numer % __denom; |
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78 |
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79 // But the modulo is implementation-defined for -ve numbers (ISO C 6.3.5) |
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80 // and we are required to "round" to zero (ISO C 7.10.6.2) |
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81 // |
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82 // The cases we have to deal with are inexact division of: |
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83 // a) + div + |
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84 // b) + div - |
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85 // c) - div + |
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86 // d) - div - |
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87 // |
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88 // a) can never go wrong and the quotient and remainder are always positive |
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89 // b) only goes wrong if the negative quotient has been "rounded" to |
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90 // -infinity - if so then the remainder will be negative when it |
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91 // should be positive or zero |
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92 // c) only goes wrong if the negative quotient has been "rounded" to |
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93 // -infinity - if so then the remainder will be positive when it |
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94 // should be negative or zero |
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95 // d) only goes wrong if the positive quotient has been rounded to |
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96 // +infinity - if so then the remainder will be positive when it |
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97 // should be negative or zero |
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98 // |
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99 // So the correct sign of the remainder corresponds to the sign of the |
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100 // numerator. Which means we can say that the result needs adjusting |
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101 // iff the sign of the numerator is different from the sign of the |
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102 // remainder. |
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103 // |
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104 // You may be interested to know that the Berkeley version of div() |
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105 // would get this wrong for (c) and (d) on some targets. |
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106 // e.g. for (-5)/4 it could leave the result as -2R3 |
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107 |
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108 if ((__ret.rem < 0) && (__numer > 0)) { |
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109 ++__ret.quot; |
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110 __ret.rem -= __denom; |
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111 } else if ((__ret.rem > 0) && (__numer < 0)) { |
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112 --__ret.quot; |
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113 __ret.rem += __denom; |
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114 } // else |
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115 |
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116 CYG_REPORT_RETVAL( __ret.quot ); |
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117 |
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118 return __ret; |
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119 } // __div() |
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120 |
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121 |
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122 // EXPORTED SYMBOLS |
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123 |
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124 externC div_t |
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125 div( int __numer, int __denom ) CYGBLD_ATTRIB_WEAK_ALIAS(__div); |
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126 |
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127 |
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128 // EOF div.cxx |
