libavutil: Utility code from libavcodec moved to a separate library.

Originally committed as revision 4489 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 110 insertions, 0 deletions

diff --git a/libavutil/rational.c b/libavutil/rational.c
new file mode 100644
index 0000000000..1044999291
--- /dev/null
+++ b/libavutil/rational.c
@@ -0,0 +1,110 @@
+/*
+ * Rational numbers
+ * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
+ *
+ * This library 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 of the License, or (at your option) any later version.
+ *
+ * This library 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 this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+ *
+ */
+ 
+/**
+ * @file rational.c
+ * Rational numbers
+ * @author Michael Niedermayer <michaelni@gmx.at>
+ */
+
+//#include <math.h>
+#include <limits.h>
+ 
+#include "common.h"
+#include "mathematics.h"
+#include "rational.h"
+
+int av_reduce(int *dst_nom, int *dst_den, int64_t nom, int64_t den, int64_t max){
+    AVRational a0={0,1}, a1={1,0};
+    int sign= (nom<0) ^ (den<0);
+    int64_t gcd= ff_gcd(ABS(nom), ABS(den));
+
+    nom = ABS(nom)/gcd;
+    den = ABS(den)/gcd;
+    if(nom<=max && den<=max){
+        a1= (AVRational){nom, den};
+        den=0;
+    }
+    
+    while(den){
+        int64_t x       = nom / den;
+        int64_t next_den= nom - den*x;
+        int64_t a2n= x*a1.num + a0.num;
+        int64_t a2d= x*a1.den + a0.den;
+
+        if(a2n > max || a2d > max) break;
+
+        a0= a1;
+        a1= (AVRational){a2n, a2d};
+        nom= den;
+        den= next_den;
+    }
+    assert(ff_gcd(a1.num, a1.den) == 1);
+    
+    *dst_nom = sign ? -a1.num : a1.num;
+    *dst_den = a1.den;
+    
+    return den==0;
+}
+
+/**
+ * returns b*c.
+ */
+AVRational av_mul_q(AVRational b, AVRational c){
+    av_reduce(&b.num, &b.den, b.num * (int64_t)c.num, b.den * (int64_t)c.den, INT_MAX);
+    return b;
+}
+
+/**
+ * returns b/c.
+ */
+AVRational av_div_q(AVRational b, AVRational c){
+    av_reduce(&b.num, &b.den, b.num * (int64_t)c.den, b.den * (int64_t)c.num, INT_MAX);
+    return b;
+}
+
+/**
+ * returns b+c.
+ */
+AVRational av_add_q(AVRational b, AVRational c){
+    av_reduce(&b.num, &b.den, b.num * (int64_t)c.den + c.num * (int64_t)b.den, b.den * (int64_t)c.den, INT_MAX);
+    return b;
+}
+
+/**
+ * returns b-c.
+ */
+AVRational av_sub_q(AVRational b, AVRational c){
+    av_reduce(&b.num, &b.den, b.num * (int64_t)c.den - c.num * (int64_t)b.den, b.den * (int64_t)c.den, INT_MAX);
+    return b;
+}
+
+/**
+ * Converts a double precission floating point number to a AVRational.
+ * @param max the maximum allowed numerator and denominator
+ */
+AVRational av_d2q(double d, int max){
+    AVRational a;
+    int exponent= FFMAX( (int)(log(ABS(d) + 1e-20)/log(2)), 0);
+    int64_t den= 1LL << (61 - exponent);
+    av_reduce(&a.num, &a.den, (int64_t)(d * den + 0.5), den, max);
+
+    return a;
+}