From decade55c63a802e288beb718de5d6b3cb81b0cc Mon Sep 17 00:00:00 2001
From: cinap_lenrek <cinap_lenrek@gmx.de>
Date: Wed, 1 May 2013 16:44:04 +0200
Subject: frexp: handle NaN values (from sources)

---
 sys/src/ape/lib/ap/plan9/frexp.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

(limited to 'sys/src/ape/lib/ap/plan9')

diff --git a/sys/src/ape/lib/ap/plan9/frexp.c b/sys/src/ape/lib/ap/plan9/frexp.c
index 588f90cee..0d81f52c7 100644
--- a/sys/src/ape/lib/ap/plan9/frexp.c
+++ b/sys/src/ape/lib/ap/plan9/frexp.c
@@ -6,6 +6,7 @@
 #define	MASK	0x7ffL
 #define	SHIFT	20
 #define	BIAS	1022L
+#define	SIG	52
 
 typedef	union
 {
@@ -25,13 +26,18 @@ typedef	union
 double
 frexp(double d, int *ep)
 {
-	Cheat x;
+	Cheat x, a;
 
-	if(d == 0) {
-		*ep = 0;
-		return 0;
-	}
+	*ep = 0;
+	/* order matters: only isNaN can operate on NaN */
+	if(isNaN(d) || isInf(d, 0) || d == 0)
+		return d;
 	x.d = d;
+	a.d = fabs(d);
+	if((a.ms >> SHIFT) == 0){	/* normalize subnormal numbers */
+		x.d = (double)(1ULL<<SIG) * d;
+		*ep = -SIG;
+	}
 	*ep = ((x.ms >> SHIFT) & MASK) - BIAS;
 	x.ms &= ~(MASK << SHIFT);
 	x.ms |= BIAS << SHIFT;
-- 
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