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  1. /*
  2.  * Copyright (C) 2006 Josef Cejka
  3.  * All rights reserved.
  4.  *
  5.  * Redistribution and use in source and binary forms, with or without
  6.  * modification, are permitted provided that the following conditions
  7.  * are met:
  8.  *
  9.  * - Redistributions of source code must retain the above copyright
  10.  *   notice, this list of conditions and the following disclaimer.
  11.  * - Redistributions in binary form must reproduce the above copyright
  12.  *   notice, this list of conditions and the following disclaimer in the
  13.  *   documentation and/or other materials provided with the distribution.
  14.  * - The name of the author may not be used to endorse or promote products
  15.  *   derived from this software without specific prior written permission.
  16.  *
  17.  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  18.  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  19.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  20.  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  21.  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  22.  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  23.  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  24.  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  25.  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  26.  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  27.  */
  28.  
  29. /** @addtogroup softint
  30.  * @{
  31.  */
  32. /**
  33.  * @file
  34.  * SW implementation of 32 and 64 bit division and modulo.
  35.  */
  36.  
  37. #include <division.h>
  38.  
  39. #define ABSVAL(x) ( (x) > 0 ? (x) : -(x))
  40. #define SGN(x) ( (x) >= 0 ? 1 : 0 )
  41.                      
  42. static unsigned int divandmod32(unsigned int a, unsigned int b, unsigned int *remainder)
  43. {
  44.     unsigned int result;
  45.     int steps = sizeof(unsigned int) * 8;
  46.    
  47.     *remainder = 0;
  48.     result = 0;
  49.    
  50.     if (b == 0) {
  51.         /* FIXME: division by zero */
  52.         return 0;
  53.     }
  54.    
  55.     if ( a < b) {
  56.         *remainder = a;
  57.         return 0;
  58.     }
  59.  
  60.     for ( ; steps > 0; steps--) {
  61.         /* shift one bit to remainder */
  62.         *remainder = ( (*remainder) << 1) | (( a >> 31) & 0x1);
  63.         result <<= 1;
  64.        
  65.         if (*remainder >= b) {
  66.                 *remainder -= b;
  67.                 result |= 0x1;
  68.         }
  69.         a <<= 1;
  70.     }
  71.  
  72.     return result;
  73. }
  74.  
  75.  
  76. static unsigned long long divandmod64(unsigned long long a, unsigned long long b, unsigned long long *remainder)
  77. {
  78.     unsigned long long result;
  79.     int steps = sizeof(unsigned long long) * 8;
  80.    
  81.     *remainder = 0;
  82.     result = 0;
  83.    
  84.     if (b == 0) {
  85.         /* FIXME: division by zero */
  86.         return 0;
  87.     }
  88.    
  89.     if ( a < b) {
  90.         *remainder = a;
  91.         return 0;
  92.     }
  93.  
  94.     for ( ; steps > 0; steps--) {
  95.         /* shift one bit to remainder */
  96.         *remainder = ( (*remainder) << 1) | ((a >> 63) & 0x1);
  97.         result <<= 1;
  98.        
  99.         if (*remainder >= b) {
  100.                 *remainder -= b;
  101.                 result |= 0x1;
  102.         }
  103.         a <<= 1;
  104.     }
  105.  
  106.     return result;
  107. }
  108.  
  109. /* 32bit integer division */
  110. int __divsi3(int a, int b)
  111. {
  112.     unsigned int rem;
  113.     int result;
  114.    
  115.     result = (int)divandmod32(ABSVAL(a), ABSVAL(b), &rem);
  116.  
  117.     if ( SGN(a) == SGN(b)) return result;
  118.     return -result;
  119. }
  120.  
  121. /* 64bit integer division */
  122. long long __divdi3(long long a, long long b)
  123. {
  124.     unsigned long long rem;
  125.     long long result;
  126.    
  127.     result = (long long)divandmod64(ABSVAL(a), ABSVAL(b), &rem);
  128.  
  129.     if ( SGN(a) == SGN(b)) return result;
  130.     return -result;
  131. }
  132.  
  133. /* 32bit unsigned integer division */
  134. unsigned int __udivsi3(unsigned int a, unsigned int b)
  135. {
  136.     unsigned int rem;
  137.     return divandmod32(a, b, &rem);
  138. }
  139.  
  140. /* 64bit unsigned integer division */
  141. unsigned long long __udivdi3(unsigned long long a, unsigned long long b)
  142. {
  143.     unsigned long long  rem;
  144.     return divandmod64(a, b, &rem);
  145. }
  146.  
  147. /* 32bit remainder of the signed division */
  148. int __modsi3(int a, int b)
  149. {
  150.     unsigned int rem;
  151.     divandmod32(a, b, &rem);
  152.    
  153.     /* if divident is negative, remainder must be too */
  154.     if (!(SGN(a))) {
  155.         return -((int)rem);
  156.     }
  157.    
  158.     return (int)rem;
  159. }
  160.  
  161. /* 64bit remainder of the signed division */
  162. long long __moddi3(long long a,long  long b)
  163. {
  164.     unsigned long long rem;
  165.     divandmod64(a, b, &rem);
  166.    
  167.     /* if divident is negative, remainder must be too */
  168.     if (!(SGN(a))) {
  169.         return -((long long)rem);
  170.     }
  171.    
  172.     return (long long)rem;
  173. }
  174.  
  175. /* 32bit remainder of the unsigned division */
  176. unsigned int __umodsi3(unsigned int a, unsigned int b)
  177. {
  178.     unsigned int rem;
  179.     divandmod32(a, b, &rem);
  180.     return rem;
  181. }
  182.  
  183. /* 64bit remainder of the unsigned division */
  184. unsigned long long __umoddi3(unsigned long long a, unsigned long long b)
  185. {
  186.     unsigned long long rem;
  187.     divandmod64(a, b, &rem);
  188.     return rem;
  189. }
  190.  
  191. unsigned long long __udivmoddi3(unsigned long long a, unsigned long long b, unsigned long long *c)
  192. {
  193.     return divandmod64(a, b, c);
  194. }
  195.  
  196. /** @}
  197.  */
  198.