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libavutil/softfloat.h

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00001 /*
00002  * Copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
00003  *
00004  * This file is part of FFmpeg.
00005  *
00006  * FFmpeg is free software; you can redistribute it and/or
00007  * modify it under the terms of the GNU Lesser General Public
00008  * License as published by the Free Software Foundation; either
00009  * version 2.1 of the License, or (at your option) any later version.
00010  *
00011  * FFmpeg is distributed in the hope that it will be useful,
00012  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00013  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00014  * Lesser General Public License for more details.
00015  *
00016  * You should have received a copy of the GNU Lesser General Public
00017  * License along with FFmpeg; if not, write to the Free Software
00018  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00019  */
00020 
00021 #ifndef AVUTIL_SOFTFLOAT_H
00022 #define AVUTIL_SOFTFLOAT_H
00023 
00024 #include <stdint.h>
00025 #include "common.h"
00026 
00027 #define MIN_EXP -126
00028 #define MAX_EXP  126
00029 #define ONE_BITS 29
00030 
00031 typedef struct SoftFloat{
00032     int32_t  exp;
00033     int32_t mant;
00034 }SoftFloat;
00035 
00036 static av_const SoftFloat av_normalize_sf(SoftFloat a){
00037     if(a.mant){
00038 #if 1
00039         while((a.mant + 0x20000000U)<0x40000000U){
00040             a.mant += a.mant;
00041             a.exp  -= 1;
00042         }
00043 #else
00044         int s=ONE_BITS + 1 - av_log2(a.mant ^ (a.mant<<1));
00045         a.exp   -= s;
00046         a.mant <<= s;
00047 #endif
00048         if(a.exp < MIN_EXP){
00049             a.exp = MIN_EXP;
00050             a.mant= 0;
00051         }
00052     }else{
00053         a.exp= MIN_EXP;
00054     }
00055     return a;
00056 }
00057 
00058 static inline av_const SoftFloat av_normalize1_sf(SoftFloat a){
00059 #if 1
00060     if(a.mant + 0x40000000 < 0){
00061         a.exp++;
00062         a.mant>>=1;
00063     }
00064     return a;
00065 #elif 1
00066     int t= a.mant + 0x40000000 < 0;
00067     return (SoftFloat){a.exp+t, a.mant>>t};
00068 #else
00069     int t= (a.mant + 0x40000000U)>>31;
00070     return (SoftFloat){a.exp+t, a.mant>>t};
00071 #endif
00072 }
00073 
00079 static inline av_const SoftFloat av_mul_sf(SoftFloat a, SoftFloat b){
00080     a.exp += b.exp;
00081     a.mant = (a.mant * (int64_t)b.mant) >> ONE_BITS;
00082     return av_normalize1_sf(a);
00083 }
00084 
00089 static av_const SoftFloat av_div_sf(SoftFloat a, SoftFloat b){
00090     a.exp -= b.exp+1;
00091     a.mant = ((int64_t)a.mant<<(ONE_BITS+1)) / b.mant;
00092     return av_normalize1_sf(a);
00093 }
00094 
00095 static inline av_const int av_cmp_sf(SoftFloat a, SoftFloat b){
00096     int t= a.exp - b.exp;
00097     if(t<0) return (a.mant >> (-t)) -  b.mant      ;
00098     else    return  a.mant          - (b.mant >> t);
00099 }
00100 
00101 static inline av_const SoftFloat av_add_sf(SoftFloat a, SoftFloat b){
00102     int t= a.exp - b.exp;
00103     if(t<0) return av_normalize1_sf((SoftFloat){b.exp, b.mant + (a.mant >> (-t))});
00104     else    return av_normalize1_sf((SoftFloat){a.exp, a.mant + (b.mant >>   t )});
00105 }
00106 
00107 static inline av_const SoftFloat av_sub_sf(SoftFloat a, SoftFloat b){
00108     return av_add_sf(a, (SoftFloat){b.exp, -b.mant});
00109 }
00110 
00111 //FIXME sqrt, log, exp, pow, sin, cos
00112 
00113 static inline av_const SoftFloat av_int2sf(int v, int frac_bits){
00114     return av_normalize_sf((SoftFloat){ONE_BITS-frac_bits, v});
00115 }
00116 
00120 static inline av_const int av_sf2int(SoftFloat v, int frac_bits){
00121     v.exp += frac_bits - ONE_BITS;
00122     if(v.exp >= 0) return v.mant <<  v.exp ;
00123     else           return v.mant >>(-v.exp);
00124 }
00125 
00126 #endif /* AVUTIL_SOFTFLOAT_H */

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