--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libavutil/softfloat.h	Wed Nov 16 11:16:33 2016 +0200
@@ -0,0 +1,132 @@
+/*
+ * Copyright (c) 2006 Michael Niedermayer <michaelni@gmx.at>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVUTIL_SOFTFLOAT_H
+#define AVUTIL_SOFTFLOAT_H
+
+#include <stdint.h>
+#include "common.h"
+
+#include "avassert.h"
+
+#define MIN_EXP -126
+#define MAX_EXP  126
+#define ONE_BITS 29
+
+typedef struct SoftFloat{
+    int32_t  exp;
+    int32_t mant;
+}SoftFloat;
+
+static av_const SoftFloat av_normalize_sf(SoftFloat a){
+    if(a.mant){
+#if 1
+        while((a.mant + 0x20000000U)<0x40000000U){
+            a.mant += a.mant;
+            a.exp  -= 1;
+        }
+#else
+        int s=ONE_BITS + 1 - av_log2(a.mant ^ (a.mant<<1));
+        a.exp   -= s;
+        a.mant <<= s;
+#endif
+        if(a.exp < MIN_EXP){
+            a.exp = MIN_EXP;
+            a.mant= 0;
+        }
+    }else{
+        a.exp= MIN_EXP;
+    }
+    return a;
+}
+
+static inline av_const SoftFloat av_normalize1_sf(SoftFloat a){
+#if 1
+    if((int32_t)(a.mant + 0x40000000U) < 0){
+        a.exp++;
+        a.mant>>=1;
+    }
+    av_assert2(a.mant < 0x40000000 && a.mant > -0x40000000);
+    return a;
+#elif 1
+    int t= a.mant + 0x40000000 < 0;
+    return (SoftFloat){a.exp+t, a.mant>>t};
+#else
+    int t= (a.mant + 0x40000000U)>>31;
+    return (SoftFloat){a.exp+t, a.mant>>t};
+#endif
+}
+
+/**
+ * @return Will not be more denormalized than a+b. So if either input is
+ *         normalized, then the output will not be worse then the other input.
+ *         If both are normalized, then the output will be normalized.
+ */
+static inline av_const SoftFloat av_mul_sf(SoftFloat a, SoftFloat b){
+    a.exp += b.exp;
+    av_assert2((int32_t)((a.mant * (int64_t)b.mant) >> ONE_BITS) == (a.mant * (int64_t)b.mant) >> ONE_BITS);
+    a.mant = (a.mant * (int64_t)b.mant) >> ONE_BITS;
+    return av_normalize1_sf(a);
+}
+
+/**
+ * b has to be normalized and not zero.
+ * @return Will not be more denormalized than a.
+ */
+static av_const SoftFloat av_div_sf(SoftFloat a, SoftFloat b){
+    a.exp -= b.exp+1;
+    a.mant = ((int64_t)a.mant<<(ONE_BITS+1)) / b.mant;
+    return av_normalize1_sf(a);
+}
+
+static inline av_const int av_cmp_sf(SoftFloat a, SoftFloat b){
+    int t= a.exp - b.exp;
+    if(t<0) return (a.mant >> (-t)) -  b.mant      ;
+    else    return  a.mant          - (b.mant >> t);
+}
+
+static inline av_const SoftFloat av_add_sf(SoftFloat a, SoftFloat b){
+    int t= a.exp - b.exp;
+    if      (t <-31) return b;
+    else if (t <  0) return av_normalize1_sf((SoftFloat){b.exp, b.mant + (a.mant >> (-t))});
+    else if (t < 32) return av_normalize1_sf((SoftFloat){a.exp, a.mant + (b.mant >>   t )});
+    else             return a;
+}
+
+static inline av_const SoftFloat av_sub_sf(SoftFloat a, SoftFloat b){
+    return av_add_sf(a, (SoftFloat){b.exp, -b.mant});
+}
+
+//FIXME sqrt, log, exp, pow, sin, cos
+
+static inline av_const SoftFloat av_int2sf(int v, int frac_bits){
+    return av_normalize_sf((SoftFloat){ONE_BITS-frac_bits, v});
+}
+
+/**
+ * Rounding is to -inf.
+ */
+static inline av_const int av_sf2int(SoftFloat v, int frac_bits){
+    v.exp += frac_bits - ONE_BITS;
+    if(v.exp >= 0) return v.mant <<  v.exp ;
+    else           return v.mant >>(-v.exp);
+}
+
+#endif /* AVUTIL_SOFTFLOAT_H */