1 files changed, 122 insertions, 0 deletions
diff --git a/libc/bionic/ldexp.c b/libc/bionic/ldexp.c
new file mode 100644
index 0000000..ec1f3dd
--- /dev/null
+++ b/libc/bionic/ldexp.c
@@ -0,0 +1,122 @@
+/* @(#)s_scalbn.c 5.1 93/09/24 */
+/* @(#)fdlibm.h 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.
+ * ====================================================
+ */
+
+#include <sys/cdefs.h>
+
+#include <sys/types.h>
+#include <endian.h>
+#include <math.h>
+
+/* Bit fiddling routines copied from msun/src/math_private.h,v 1.15 */
+
+#if BYTE_ORDER == BIG_ENDIAN
+
+typedef union
+{
+  double value;
+  struct
+  {
+    u_int32_t msw;
+    u_int32_t lsw;
+  } parts;
+} ieee_double_shape_type;
+
+#endif
+
+#if BYTE_ORDER == LITTLE_ENDIAN
+
+typedef union
+{
+  double value;
+  struct
+  {
+    u_int32_t lsw;
+    u_int32_t msw;
+  } parts;
+} ieee_double_shape_type;
+
+#endif
+
+/* Get two 32 bit ints from a double.  */
+
+#define EXTRACT_WORDS(ix0,ix1,d)				\
+do {								\
+  ieee_double_shape_type ew_u;					\
+  ew_u.value = (d);						\
+  (ix0) = ew_u.parts.msw;					\
+  (ix1) = ew_u.parts.lsw;					\
+} while (0)
+
+/* Get the more significant 32 bit int from a double.  */
+
+#define GET_HIGH_WORD(i,d)					\
+do {								\
+  ieee_double_shape_type gh_u;					\
+  gh_u.value = (d);						\
+  (i) = gh_u.parts.msw;						\
+} while (0)
+
+/* Set the more significant 32 bits of a double from an int.  */
+
+#define SET_HIGH_WORD(d,v)					\
+do {								\
+  ieee_double_shape_type sh_u;					\
+  sh_u.value = (d);						\
+  sh_u.parts.msw = (v);						\
+  (d) = sh_u.value;						\
+} while (0)
+
+
+static const double
+two54   =  1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
+twom54  =  5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
+huge   = 1.0e+300,
+tiny   = 1.0e-300;
+
+static double
+_copysign(double x, double y)
+{
+	u_int32_t hx,hy;
+	GET_HIGH_WORD(hx,x);
+	GET_HIGH_WORD(hy,y);
+	SET_HIGH_WORD(x,(hx&0x7fffffff)|(hy&0x80000000));
+	return x;
+}
+
+double
+ldexp(double x, int n)
+{
+	int32_t k,hx,lx;
+	EXTRACT_WORDS(hx,lx,x);
+        k = (hx&0x7ff00000)>>20;		/* extract exponent */
+        if (k==0) {				/* 0 or subnormal x */
+            if ((lx|(hx&0x7fffffff))==0) return x; /* +-0 */
+	    x *= two54;
+	    GET_HIGH_WORD(hx,x);
+	    k = ((hx&0x7ff00000)>>20) - 54;
+            if (n< -50000) return tiny*x; 	/*underflow*/
+	    }
+        if (k==0x7ff) return x+x;		/* NaN or Inf */
+        k = k+n;
+        if (k >  0x7fe) return huge*_copysign(huge,x); /* overflow  */
+        if (k > 0) 				/* normal result */
+	    {SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20)); return x;}
+        if (k <= -54) {
+            if (n > 50000) 	/* in case integer overflow in n+k */
+		return huge*_copysign(huge,x);	/*overflow*/
+	    else return tiny*_copysign(tiny,x); 	/*underflow*/
+	}
+        k += 54;				/* subnormal result */
+	SET_HIGH_WORD(x,(hx&0x800fffff)|(k<<20));
+        return x*twom54;
+}