//=========================================================================== // // div.cxx // // ISO C implementation for div() utility function // //=========================================================================== //####COPYRIGHTBEGIN#### // // ------------------------------------------- // The contents of this file are subject to the Red Hat eCos Public License // Version 1.1 (the "License"); you may not use this file except in // compliance with the License. You may obtain a copy of the License at // http://www.redhat.com/ // // Software distributed under the License is distributed on an "AS IS" // basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See the // License for the specific language governing rights and limitations under // the License. // // The Original Code is eCos - Embedded Configurable Operating System, // released September 30, 1998. // // The Initial Developer of the Original Code is Red Hat. // Portions created by Red Hat are // Copyright (C) 1998, 1999, 2000 Red Hat, Inc. // All Rights Reserved. // ------------------------------------------- // //####COPYRIGHTEND#### //=========================================================================== //#####DESCRIPTIONBEGIN#### // // Author(s): jlarmour // Contributors: jlarmour // Date: 1999-03-02 // Purpose: Provide implementation of div() from ISO C section 7.10.6.2 // Description: // Usage: // //####DESCRIPTIONEND#### // //=========================================================================== // // CONFIGURATION #include // Configuration header // INCLUDES #include // Common type definitions and support #include // Assertion support #include // Tracing support // We don't want the inline versions of stdlib functions defined here #ifdef CYGIMP_LIBC_STDLIB_INLINES # undef CYGIMP_LIBC_STDLIB_INLINES #endif #include // NULL, wchar_t and size_t from compiler #include // Main header for stdlib functions // FUNCTIONS externC div_t __div( int __numer, int __denom ) { div_t __ret; CYG_REPORT_FUNCNAMETYPE( "__div", "quotient: %d"); CYG_REPORT_FUNCARG2DV( __numer, __denom ); // FIXME: what if they want it handled with SIGFPE? Should have option CYG_PRECONDITION(__denom != 0, "division by zero attempted!"); __ret.quot = __numer / __denom; __ret.rem = __numer % __denom; // But the modulo is implementation-defined for -ve numbers (ISO C 6.3.5) // and we are required to "round" to zero (ISO C 7.10.6.2) // // The cases we have to deal with are inexact division of: // a) + div + // b) + div - // c) - div + // d) - div - // // a) can never go wrong and the quotient and remainder are always positive // b) only goes wrong if the negative quotient has been "rounded" to // -infinity - if so then the remainder will be negative when it // should be positive or zero // c) only goes wrong if the negative quotient has been "rounded" to // -infinity - if so then the remainder will be positive when it // should be negative or zero // d) only goes wrong if the positive quotient has been rounded to // +infinity - if so then the remainder will be positive when it // should be negative or zero // // So the correct sign of the remainder corresponds to the sign of the // numerator. Which means we can say that the result needs adjusting // iff the sign of the numerator is different from the sign of the // remainder. // // You may be interested to know that the Berkeley version of div() // would get this wrong for (c) and (d) on some targets. // e.g. for (-5)/4 it could leave the result as -2R3 if ((__ret.rem < 0) && (__numer > 0)) { ++__ret.quot; __ret.rem -= __denom; } else if ((__ret.rem > 0) && (__numer < 0)) { --__ret.quot; __ret.rem += __denom; } // else CYG_REPORT_RETVAL( __ret.quot ); return __ret; } // __div() // EXPORTED SYMBOLS externC div_t div( int __numer, int __denom ) CYGBLD_ATTRIB_WEAK_ALIAS(__div); // EOF div.cxx
