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-rw-r--r--src/math/s_floor.c69
1 files changed, 69 insertions, 0 deletions
diff --git a/src/math/s_floor.c b/src/math/s_floor.c
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+/* @(#)s_floor.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.
+ * ====================================================
+ */
+
+/*
+ * floor(x)
+ * Return x rounded toward -inf to integral value
+ * Method:
+ * Bit twiddling.
+ * Exception:
+ * Inexact flag raised if x not equal to floor(x).
+ */
+
+#include <math.h>
+#include "math_private.h"
+
+static const double huge = 1.0e300;
+
+double
+floor(double x)
+{
+ int32_t i0,i1,j0;
+ uint32_t i,j;
+ EXTRACT_WORDS(i0,i1,x);
+ j0 = ((i0>>20)&0x7ff)-0x3ff;
+ if(j0<20) {
+ if(j0<0) { /* raise inexact if x != 0 */
+ if(huge+x>0.0) {/* return 0*sign(x) if |x|<1 */
+ if(i0>=0) {i0=i1=0;}
+ else if(((i0&0x7fffffff)|i1)!=0)
+ { i0=0xbff00000;i1=0;}
+ }
+ } else {
+ i = (0x000fffff)>>j0;
+ if(((i0&i)|i1)==0) return x; /* x is integral */
+ if(huge+x>0.0) { /* raise inexact flag */
+ if(i0<0) i0 += (0x00100000)>>j0;
+ i0 &= (~i); i1=0;
+ }
+ }
+ } 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 */
+ if(huge+x>0.0) { /* raise inexact flag */
+ if(i0<0) {
+ if(j0==20) i0+=1;
+ else {
+ j = i1+(1<<(52-j0));
+ if(j<i1) i0 +=1 ; /* got a carry */
+ i1=j;
+ }
+ }
+ i1 &= (~i);
+ }
+ }
+ INSERT_WORDS(x,i0,i1);
+ return x;
+}