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+/*******************************************************************************
+* *
+* File frexpldexp.c, *
+* Functions frexp(x) and ldexp(x), *
+* Implementation of frexp and ldexp functions for the PowerPC. *
+* *
+* Copyright © 1991 Apple Computer, Inc. All rights reserved. *
+* *
+* Written by Ali Sazegari, started on January 1991, *
+* *
+* W A R N I N G: This routine expects a 64 bit double model. *
+* *
+* December03 1992: first rs6000 implementation. *
+* October 05 1993: added special cases for NaN and ° in frexp. *
+* May 27 1997: improved the performance of frexp by eliminating the *
+* switch statement. *
+* June 13 2001: (ram) rewrote frexp to eliminate calls to scalb and *
+* logb. *
+* *
+*******************************************************************************/
+
+#include <limits.h>
+#include <math.h>
+
+static const double two54 = 1.80143985094819840000e+16; /* 0x43500000, 0x00000000 */
+
+typedef union
+ {
+ struct {
+#if defined(__BIG_ENDIAN__)
+ unsigned long int hi;
+ unsigned long int lo;
+#else
+ unsigned long int lo;
+ unsigned long int hi;
+#endif
+ } words;
+ double dbl;
+ } DblInHex;
+
+double frexp ( double value, int *eptr )
+ {
+ DblInHex argument;
+ unsigned long int valueHead;
+
+ argument.dbl = value;
+ valueHead = argument.words.hi & 0x7fffffffUL; // valueHead <- |x|
+
+ *eptr = 0;
+ if ( valueHead >= 0x7ff00000 || ( valueHead | argument.words.lo ) == 0 )
+ return value; // 0, inf, or NaN
+
+ if ( valueHead < 0x00100000 )
+ { // denorm
+ argument.dbl = two54 * value;
+ valueHead = argument.words.hi &0x7fffffff;
+ *eptr = -54;
+ }
+ *eptr += ( valueHead >> 20 ) - 1022;
+ argument.words.hi = ( argument.words.hi & 0x800fffff ) | 0x3fe00000;
+ return argument.dbl;
+ }
+