From 0b44a0315b47dd8eced9f3b7f31580cf14bbfc01 Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Sat, 12 Feb 2011 00:22:29 -0500
Subject: initial check-in, version 0.5.0

---
 src/math/e_atan2f.c | 93 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 93 insertions(+)
 create mode 100644 src/math/e_atan2f.c

(limited to 'src/math/e_atan2f.c')

diff --git a/src/math/e_atan2f.c b/src/math/e_atan2f.c
new file mode 100644
index 00000000..535e10a0
--- /dev/null
+++ b/src/math/e_atan2f.c
@@ -0,0 +1,93 @@
+/* e_atan2f.c -- float version of e_atan2.c.
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ */
+
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+
+#include <math.h>
+#include "math_private.h"
+
+static const float
+tiny  = 1.0e-30,
+zero  = 0.0,
+pi_o_4  = 7.8539818525e-01, /* 0x3f490fdb */
+pi_o_2  = 1.5707963705e+00, /* 0x3fc90fdb */
+pi      = 3.1415927410e+00, /* 0x40490fdb */
+pi_lo   = -8.7422776573e-08; /* 0xb3bbbd2e */
+
+float
+atan2f(float y, float x)
+{
+        float z;
+        int32_t k,m,hx,hy,ix,iy;
+
+        GET_FLOAT_WORD(hx,x);
+        ix = hx&0x7fffffff;
+        GET_FLOAT_WORD(hy,y);
+        iy = hy&0x7fffffff;
+        if((ix>0x7f800000)||
+           (iy>0x7f800000))     /* x or y is NaN */
+           return x+y;
+        if(hx==0x3f800000) return atanf(y);   /* x=1.0 */
+        m = ((hy>>31)&1)|((hx>>30)&2);  /* 2*sign(x)+sign(y) */
+
+    /* when y = 0 */
+        if(iy==0) {
+            switch(m) {
+                case 0:
+                case 1: return y;       /* atan(+-0,+anything)=+-0 */
+                case 2: return  pi+tiny;/* atan(+0,-anything) = pi */
+                case 3: return -pi-tiny;/* atan(-0,-anything) =-pi */
+            }
+        }
+    /* when x = 0 */
+        if(ix==0) return (hy<0)?  -pi_o_2-tiny: pi_o_2+tiny;
+
+    /* when x is INF */
+        if(ix==0x7f800000) {
+            if(iy==0x7f800000) {
+                switch(m) {
+                    case 0: return  pi_o_4+tiny;/* atan(+INF,+INF) */
+                    case 1: return -pi_o_4-tiny;/* atan(-INF,+INF) */
+                    case 2: return  (float)3.0*pi_o_4+tiny;/*atan(+INF,-INF)*/
+                    case 3: return (float)-3.0*pi_o_4-tiny;/*atan(-INF,-INF)*/
+                }
+            } else {
+                switch(m) {
+                    case 0: return  zero  ;     /* atan(+...,+INF) */
+                    case 1: return -zero  ;     /* atan(-...,+INF) */
+                    case 2: return  pi+tiny  ;  /* atan(+...,-INF) */
+                    case 3: return -pi-tiny  ;  /* atan(-...,-INF) */
+                }
+            }
+        }
+    /* when y is INF */
+        if(iy==0x7f800000) return (hy<0)? -pi_o_2-tiny: pi_o_2+tiny;
+
+    /* compute y/x */
+        k = (iy-ix)>>23;
+        if(k > 60) z=pi_o_2+(float)0.5*pi_lo;   /* |y/x| >  2**60 */
+        else if(hx<0&&k<-60) z=0.0;     /* |y|/x < -2**60 */
+        else z=atanf(fabsf(y/x));       /* safe to do y/x */
+        switch (m) {
+            case 0: return       z  ;   /* atan(+,+) */
+            case 1: {
+                      uint32_t zh;
+                      GET_FLOAT_WORD(zh,z);
+                      SET_FLOAT_WORD(z,zh ^ 0x80000000);
+                    }
+                    return       z  ;   /* atan(-,+) */
+            case 2: return  pi-(z-pi_lo);/* atan(+,-) */
+            default: /* case 3 */
+                    return  (z-pi_lo)-pi;/* atan(-,-) */
+        }
+}
-- 
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