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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 SoftInt
  30.  * @brief   Software implementation of basic arithmetic operations.
  31.  * @{
  32.  */
  33. /**
  34.  * @file
  35.  * SW implementation of 32 and 64 bit division and modulo.
  36.  */
  37.  
  38. #include <division.h>
  39.  
  40. #define ABSVAL(x) ( (x) > 0 ? (x) : -(x))
  41. #define SGN(x) ( (x) >= 0 ? 1 : 0 )
  42.                      
  43. static unsigned int divandmod32(unsigned int a, unsigned int b, unsigned int *remainder)
  44. {
  45.     unsigned int result;
  46.     int steps = sizeof(unsigned int) * 8;
  47.    
  48.     *remainder = 0;
  49.     result = 0;
  50.    
  51.     if (b == 0) {
  52.         /* FIXME: division by zero */
  53.         return 0;
  54.     }
  55.    
  56.     if ( a < b) {
  57.         *remainder = a;
  58.         return 0;
  59.     }
  60.  
  61.     for ( ; steps > 0; steps--) {
  62.         /* shift one bit to remainder */
  63.         *remainder = ( (*remainder) << 1) | (( a >> 31) & 0x1);
  64.         result <<= 1;
  65.        
  66.         if (*remainder >= b) {
  67.                 *remainder -= b;
  68.                 result |= 0x1;
  69.         }
  70.         a <<= 1;
  71.     }
  72.  
  73.     return result;
  74. }
  75.  
  76.  
  77. static unsigned long long divandmod64(unsigned long long a, unsigned long long b, unsigned long long *remainder)
  78. {
  79.     unsigned long long result;
  80.     int steps = sizeof(unsigned long long) * 8;
  81.    
  82.     *remainder = 0;
  83.     result = 0;
  84.    
  85.     if (b == 0) {
  86.         /* FIXME: division by zero */
  87.         return 0;
  88.     }
  89.    
  90.     if ( a < b) {
  91.         *remainder = a;
  92.         return 0;
  93.     }
  94.  
  95.     for ( ; steps > 0; steps--) {
  96.         /* shift one bit to remainder */
  97.         *remainder = ( (*remainder) << 1) | ((a >> 63) & 0x1);
  98.         result <<= 1;
  99.        
  100.         if (*remainder >= b) {
  101.                 *remainder -= b;
  102.                 result |= 0x1;
  103.         }
  104.         a <<= 1;
  105.     }
  106.  
  107.     return result;
  108. }
  109.  
  110. /* 32bit integer division */
  111. int __divsi3(int a, int b)
  112. {
  113.     unsigned int rem;
  114.     int result;
  115.    
  116.     result = (int)divandmod32(ABSVAL(a), ABSVAL(b), &rem);
  117.  
  118.     if ( SGN(a) == SGN(b)) return result;
  119.     return -result;
  120. }
  121.  
  122. /* 64bit integer division */
  123. long long __divdi3(long long a, long long b)
  124. {
  125.     unsigned long long rem;
  126.     long long result;
  127.    
  128.     result = (long long)divandmod64(ABSVAL(a), ABSVAL(b), &rem);
  129.  
  130.     if ( SGN(a) == SGN(b)) return result;
  131.     return -result;
  132. }
  133.  
  134. /* 32bit unsigned integer division */
  135. unsigned int __udivsi3(unsigned int a, unsigned int b)
  136. {
  137.     unsigned int rem;
  138.     return divandmod32(a, b, &rem);
  139. }
  140.  
  141. /* 64bit unsigned integer division */
  142. unsigned long long __udivdi3(unsigned long long a, unsigned long long b)
  143. {
  144.     unsigned long long  rem;
  145.     return divandmod64(a, b, &rem);
  146. }
  147.  
  148. /* 32bit remainder of the signed division */
  149. int __modsi3(int a, int b)
  150. {
  151.     unsigned int rem;
  152.     divandmod32(a, b, &rem);
  153.    
  154.     /* if divident is negative, remainder must be too */
  155.     if (!(SGN(a))) {
  156.         return -((int)rem);
  157.     }
  158.    
  159.     return (int)rem;
  160. }
  161.  
  162. /* 64bit remainder of the signed division */
  163. long long __moddi3(long long a,long  long b)
  164. {
  165.     unsigned long long rem;
  166.     divandmod64(a, b, &rem);
  167.    
  168.     /* if divident is negative, remainder must be too */
  169.     if (!(SGN(a))) {
  170.         return -((long long)rem);
  171.     }
  172.    
  173.     return (long long)rem;
  174. }
  175.  
  176. /* 32bit remainder of the unsigned division */
  177. unsigned int __umodsi3(unsigned int a, unsigned int b)
  178. {
  179.     unsigned int rem;
  180.     divandmod32(a, b, &rem);
  181.     return rem;
  182. }
  183.  
  184. /* 64bit remainder of the unsigned division */
  185. unsigned long long __umoddi3(unsigned long long a, unsigned long long b)
  186. {
  187.     unsigned long long rem;
  188.     divandmod64(a, b, &rem);
  189.     return rem;
  190. }
  191.  
  192. unsigned long long __udivmoddi3(unsigned long long a, unsigned long long b, unsigned long long *c)
  193. {
  194.     return divandmod64(a, b, c);
  195. }
  196.  
  197. /** @}
  198.  */
  199.