avutil: Softfloat implementation for IEEE 754 floating point

Signed-off-by: Umair Khan <omerjerk@gmail.com>

libavutil/softfloat_ieee754.h

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+/*
+ * Copyright (c) 2016 Umair Khan <omerjerk@gmail.com>
+ *
+ * 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_IEEE754_H
+#define AVUTIL_SOFTFLOAT_IEEE754_H
+
+#include <stdint.h>
+
+#define EXP_BIAS 127
+#define MANT_BITS 23
+
+typedef struct SoftFloat_IEEE754 {
+    int32_t sign;
+    uint64_t mant;
+    int32_t  exp;
+} SoftFloat_IEEE754;
+
+static const SoftFloat_IEEE754 FLOAT_0 = {0, 0, -126};
+static const SoftFloat_IEEE754 FLOAT_1 = {0, 0,    0};
+
+/** Normalize the softfloat as defined by IEEE 754 single-recision floating
+ *  point specification
+ */
+static SoftFloat_IEEE754 av_normalize_sf_ieee754(SoftFloat_IEEE754 sf) {
+    while( sf.mant >= 0x1000000UL ) {
+        sf.exp++;
+        sf.mant >>= 1;
+    }
+    sf.mant &= 0x007fffffUL;
+    return sf;
+}
+
+/** Convert integer to softfloat.
+ *  @return softfloat with value n * 2^e
+ */
+static SoftFloat_IEEE754 av_int2sf_ieee754(int64_t n, int e) {
+    int sign = 0;
+
+    if (n < 0) {
+        sign = 1;
+        n    *= -1;
+    }
+    return av_normalize_sf_ieee754((SoftFloat_IEEE754) {sign, n << MANT_BITS, 0 + e});
+}
+
+/** Make a softfloat out of the bitstream. Assumes the bits are in the form as defined
+ *  by the IEEE 754 spec.
+ */
+static SoftFloat_IEEE754 av_bits2sf_ieee754(uint32_t n) {
+    return ((SoftFloat_IEEE754) { (n & 0x80000000UL), (n & 0x7FFFFFUL), (n & 0x7F800000UL) });
+}
+
+/** Convert the softfloat to integer
+ */
+static int av_sf2int_ieee754(SoftFloat_IEEE754 a) {
+    if(a.exp >= 0) return a.mant <<  a.exp ;
+    else           return a.mant >>(-a.exp);
+}
+
+/** Divide a by b. b should not be zero.
+ *  @return normalized result
+ */
+static SoftFloat_IEEE754 av_div_sf_ieee754(SoftFloat_IEEE754 a, SoftFloat_IEEE754 b) {
+    int32_t mant, exp, sign;
+    a    = av_normalize_sf_ieee754(a);
+    b    = av_normalize_sf_ieee754(b);
+    sign = a.sign ^ b.sign;
+    mant = ((((uint64_t) (a.mant | 0x00800000UL)) << MANT_BITS) / (b.mant| 0x00800000UL));
+    exp  = a.exp - b.exp;
+    return av_normalize_sf_ieee754((SoftFloat_IEEE754) {sign, mant, exp});
+}
+
+/** Multiply a with b
+ *  #return normalized result
+ */
+static SoftFloat_IEEE754 av_mul_sf_ieee754(SoftFloat_IEEE754 a, SoftFloat_IEEE754 b) {
+    int32_t sign, mant, exp;
+    a    = av_normalize_sf_ieee754(a);
+    b    = av_normalize_sf_ieee754(b);
+    sign = a.sign ^ b.sign;
+    mant = (((uint64_t)(a.mant|0x00800000UL) * (uint64_t)(b.mant|0x00800000UL))>>MANT_BITS);
+    exp  = a.exp + b.exp;
+    return av_normalize_sf_ieee754((SoftFloat_IEEE754) {sign, mant, exp});
+}
+
+/** Compare a with b strictly
+ *  @returns 1 if the a and b are equal, 0 otherwise.
+ */
+static int av_cmp_sf_ieee754(SoftFloat_IEEE754 a, SoftFloat_IEEE754 b) {
+    a = av_normalize_sf_ieee754(a);
+    b = av_normalize_sf_ieee754(b);
+    if (a.sign != b.sign) return 0;
+    if (a.mant != b.mant) return 0;
+    if (a.exp  != b.exp ) return 0;
+    return 1;
+}
+
+#endif /*AVUTIL_SOFTFLOAT_IEEE754_H*/