Subversion Repositories HelenOS-historic

Rev

Rev 834 | Rev 1031 | Go to most recent revision | Blame | Compare with Previous | Last modification | View Log | Download | RSS feed

  1. /*
  2.  * Copyright (C) 2005 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. #include<sftypes.h>
  30. #include<common.h>
  31.  
  32. /** Take fraction shifted by 10 bits to left, round it, normalize it and detect exceptions
  33.  * @param exp exponent with bias
  34.  * @param cfrac fraction shifted 10 places left with added hidden bit
  35.  * @return valied float64
  36.  */
  37. float64 finishFloat64(__s32 cexp, __u64 cfrac, char sign)
  38. {
  39.     float64 result;
  40.  
  41.     result.parts.sign = sign;
  42.  
  43.     /* find first nonzero digit and shift result and detect possibly underflow */
  44.     while ((cexp > 0) && (cfrac) && (!(cfrac & (FLOAT64_HIDDEN_BIT_MASK << (64 - FLOAT64_FRACTION_SIZE - 1 ) )))) {
  45.         cexp--;
  46.         cfrac <<= 1;
  47.             /* TODO: fix underflow */
  48.     };
  49.    
  50.     if ((cexp < 0) || ( cexp == 0 && (!(cfrac & (FLOAT64_HIDDEN_BIT_MASK << (64 - FLOAT64_FRACTION_SIZE - 1)))))) {
  51.         /* FIXME: underflow */
  52.         result.parts.exp = 0;
  53.         if ((cexp + FLOAT64_FRACTION_SIZE + 1) < 0) { /* +1 is place for rounding */
  54.             result.parts.fraction = 0;
  55.             return result;
  56.         }
  57.        
  58.         while (cexp < 0) {
  59.             cexp++;
  60.             cfrac >>= 1;
  61.         }
  62.    
  63.         cfrac += (0x1 << (64 - FLOAT64_FRACTION_SIZE - 3));
  64.        
  65.         if (!(cfrac & (FLOAT64_HIDDEN_BIT_MASK << (64 - FLOAT64_HIDDEN_BIT_MASK - 1)))) {
  66.            
  67.             result.parts.fraction = ((cfrac >>(64 - FLOAT64_FRACTION_SIZE - 2) ) & (~FLOAT64_HIDDEN_BIT_MASK));
  68.             return result;
  69.         }  
  70.     } else {
  71.         cfrac += (0x1 << (64 - FLOAT64_FRACTION_SIZE - 3));
  72.     }
  73.    
  74.     ++cexp;
  75.  
  76.     if (cfrac & (FLOAT64_HIDDEN_BIT_MASK << (64 - FLOAT64_FRACTION_SIZE - 1 ))) {
  77.         ++cexp;
  78.         cfrac >>= 1;
  79.     }  
  80.  
  81.     /* check overflow */
  82.     if (cexp >= FLOAT64_MAX_EXPONENT ) {
  83.         /* FIXME: overflow, return infinity */
  84.         result.parts.exp = FLOAT64_MAX_EXPONENT;
  85.         result.parts.fraction = 0;
  86.         return result;
  87.     }
  88.  
  89.     result.parts.exp = (__u32)cexp;
  90.    
  91.     result.parts.fraction = ((cfrac >>(64 - FLOAT64_FRACTION_SIZE - 2 ) ) & (~FLOAT64_HIDDEN_BIT_MASK));
  92.    
  93.     return result; 
  94. }
  95.  
  96.