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/s_rint.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 80 insertions(+)
 create mode 100644 src/math/s_rint.c

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

diff --git a/src/math/s_rint.c b/src/math/s_rint.c
new file mode 100644
index 00000000..aec7d3c9
--- /dev/null
+++ b/src/math/s_rint.c
@@ -0,0 +1,80 @@
+/* @(#)s_rint.c 5.1 93/09/24 */
+/*
+ * ====================================================
+ * 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.
+ * ====================================================
+ */
+
+/*
+ * rint(x)
+ * Return x rounded to integral value according to the prevailing
+ * rounding mode.
+ * Method:
+ *      Using floating addition.
+ * Exception:
+ *      Inexact flag raised if x not equal to rint(x).
+ */
+
+#include <math.h>
+#include "math_private.h"
+
+/*
+ * TWO23 is long double instead of double to avoid a bug in gcc.  Without
+ * this, gcc thinks that TWO23[sx]+x and w-TWO23[sx] already have double
+ * precision and doesn't clip them to double precision when they are
+ * assigned and returned.
+ */
+static const long double
+TWO52[2]={
+  4.50359962737049600000e+15, /* 0x43300000, 0x00000000 */
+ -4.50359962737049600000e+15, /* 0xC3300000, 0x00000000 */
+};
+
+double
+rint(double x)
+{
+        int32_t i0,j0,sx;
+        uint32_t i,i1;
+        double w,t;
+        EXTRACT_WORDS(i0,i1,x);
+        sx = (i0>>31)&1;
+        j0 = ((i0>>20)&0x7ff)-0x3ff;
+        if(j0<20) {
+            if(j0<0) {
+                if(((i0&0x7fffffff)|i1)==0) return x;
+                i1 |= (i0&0x0fffff);
+                i0 &= 0xfffe0000;
+                i0 |= ((i1|-i1)>>12)&0x80000;
+                SET_HIGH_WORD(x,i0);
+                w = TWO52[sx]+x;
+                t =  w-TWO52[sx];
+                GET_HIGH_WORD(i0,t);
+                SET_HIGH_WORD(t,(i0&0x7fffffff)|(sx<<31));
+                return t;
+            } else {
+                i = (0x000fffff)>>j0;
+                if(((i0&i)|i1)==0) return x; /* x is integral */
+                i>>=1;
+                if(((i0&i)|i1)!=0) {
+                    if(j0==19) i1 = 0x40000000; else
+                    i0 = (i0&(~i))|((0x20000)>>j0);
+                }
+            }
+        } else if (j0>51) {
+            if(j0==0x400) return x+x;   /* inf or NaN */
+            else return x;              /* x is integral */
+        } else {
+            i = ((uint32_t)(0xffffffff))>>(j0-20);
+            if((i1&i)==0) return x;     /* x is integral */
+            i>>=1;
+            if((i1&i)!=0) i1 = (i1&(~i))|((0x40000000)>>(j0-20));
+        }
+        INSERT_WORDS(x,i0,i1);
+        w = TWO52[sx]+x;
+        return w-TWO52[sx];
+}
-- 
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