libavutil/softfloat_ieee754.h

   1 /*
   2  * Copyright (c) 2016 Umair Khan <omerjerk@gmail.com>
   3  *
   4  * This file is part of FFmpeg.
   5  *
   6  * FFmpeg is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2.1 of the License, or (at your option) any later version.
  10  *
  11  * FFmpeg is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with FFmpeg; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  19  */
  20
  21 #ifndef AVUTIL_SOFTFLOAT_IEEE754_H
  22 #define AVUTIL_SOFTFLOAT_IEEE754_H
  23
  24 #include <stdint.h>
  25
  26 #define EXP_BIAS 127
  27 #define MANT_BITS 23
  28
  29 typedef struct SoftFloat_IEEE754 {
  30     int32_t sign;
  31     uint64_t mant;
  32     int32_t  exp;
  33 } SoftFloat_IEEE754;
  34
  35 static const SoftFloat_IEEE754 FLOAT_0 = {0, 0, -126};
  36 static const SoftFloat_IEEE754 FLOAT_1 = {0, 0,    0};
  37
  38 /** Normalize the softfloat as defined by IEEE 754 single-recision floating
  39  *  point specification
  40  */
  41 static inline SoftFloat_IEEE754 av_normalize_sf_ieee754(SoftFloat_IEEE754 sf) {
  42     while( sf.mant >= 0x1000000UL ) {
  43         sf.exp++;
  44         sf.mant >>= 1;
  45     }
  46     sf.mant &= 0x007fffffUL;
  47     return sf;
  48 }
  49
  50 /** Convert integer to softfloat.
  51  *  @return softfloat with value n * 2^e
  52  */
  53 static inline SoftFloat_IEEE754 av_int2sf_ieee754(int64_t n, int e) {
  54     int sign = 0;
  55
  56     if (n < 0) {
  57         sign = 1;
  58         n    *= -1;
  59     }
  60     return av_normalize_sf_ieee754((SoftFloat_IEEE754) {sign, n << MANT_BITS, 0 + e});
  61 }
  62
  63 /** Make a softfloat out of the bitstream. Assumes the bits are in the form as defined
  64  *  by the IEEE 754 spec.
  65  */
  66 static inline SoftFloat_IEEE754 av_bits2sf_ieee754(uint32_t n) {
  67     return ((SoftFloat_IEEE754) { (n & 0x80000000UL) >> 31, (n & 0x7FFFFFUL), (int8_t)((n & 0x7F800000UL) >> 23)});
  68 }
  69
  70 /** Convert the softfloat to integer
  71  */
  72 static inline int av_sf2int_ieee754(SoftFloat_IEEE754 a) {
  73     if(a.exp >= 0) return a.mant <<  a.exp ;
  74     else           return a.mant >>(-a.exp);
  75 }
  76
  77 /** Divide a by b. b should not be zero.
  78  *  @return normalized result
  79  */
  80 static inline SoftFloat_IEEE754 av_div_sf_ieee754(SoftFloat_IEEE754 a, SoftFloat_IEEE754 b) {
  81     int32_t mant, exp, sign;
  82     a    = av_normalize_sf_ieee754(a);
  83     b    = av_normalize_sf_ieee754(b);
  84     sign = a.sign ^ b.sign;
  85     mant = ((((uint64_t) (a.mant | 0x00800000UL)) << MANT_BITS) / (b.mant| 0x00800000UL));
  86     exp  = a.exp - b.exp;
  87     return av_normalize_sf_ieee754((SoftFloat_IEEE754) {sign, mant, exp});
  88 }
  89
  90 /** Multiply a with b
  91  *  #return normalized result
  92  */
  93 static inline SoftFloat_IEEE754 av_mul_sf_ieee754(SoftFloat_IEEE754 a, SoftFloat_IEEE754 b) {
  94     int32_t sign, mant, exp;
  95     a    = av_normalize_sf_ieee754(a);
  96     b    = av_normalize_sf_ieee754(b);
  97     sign = a.sign ^ b.sign;
  98     mant = (((uint64_t)(a.mant|0x00800000UL) * (uint64_t)(b.mant|0x00800000UL))>>MANT_BITS);
  99     exp  = a.exp + b.exp;
 100     return av_normalize_sf_ieee754((SoftFloat_IEEE754) {sign, mant, exp});
 101 }
 102
 103 /** Compare a with b strictly
 104  *  @returns 1 if the a and b are equal, 0 otherwise.
 105  */
 106 static inline int av_cmp_sf_ieee754(SoftFloat_IEEE754 a, SoftFloat_IEEE754 b) {
 107     a = av_normalize_sf_ieee754(a);
 108     b = av_normalize_sf_ieee754(b);
 109     if (a.sign != b.sign) return 0;
 110     if (a.mant != b.mant) return 0;
 111     if (a.exp  != b.exp ) return 0;
 112     return 1;
 113 }
 114
 115 #endif /*AVUTIL_SOFTFLOAT_IEEE754_H*/