Import of the watch repository from Pebble

third_party/math/scalbn.c

@@ -0,0 +1,127 @@
+///////////////////////////////////////
+// Implements:
+//   double scalbn(double x, int n);
+///////////////////////////////////////
+// Notes:
+//   This is taken from newlib.
+//   Only included because pow() needs it.
+// @nolint
+
+/*
+ * ====================================================
+ * 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 <stdint.h>
+#include <pblibc_private.h>
+
+/*
+ * scalbn (double x, int n)
+ * scalbn(x,n) returns x* 2**n  computed by  exponent
+ * manipulation rather than by actually performing an
+ * exponentiation or a multiplication.
+ */
+
+static const double
+two54   =  1.80143985094819840000e+16, /* 0x43500000, 0x00000000 */
+twom54  =  5.55111512312578270212e-17, /* 0x3C900000, 0x00000000 */
+huge   = 1.0e+300,
+tiny   = 1.0e-300;
+
+typedef union
+{
+  double value;
+  struct
+  {
+    uint32_t lsw;
+    uint32_t msw;
+  } parts;
+} ieee_double_shape_type;
+
+#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)
+
+/* Get the less significant 32 bit int from a double.  */
+
+#define GET_LOW_WORD(i,d)         \
+do {                \
+  ieee_double_shape_type gl_u;          \
+  gl_u.value = (d);           \
+  (i) = gl_u.parts.lsw;           \
+} 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)
+
+/* Set the less significant 32 bits of a double from an int.  */
+
+#define SET_LOW_WORD(d,v)         \
+do {                \
+  ieee_double_shape_type sl_u;          \
+  sl_u.value = (d);           \
+  sl_u.parts.lsw = (v);           \
+  (d) = sl_u.value;           \
+} while (0)
+
+static double copysign(double x, double y)
+{
+  uint32_t hx,hy;
+  GET_HIGH_WORD(hx,x);
+  GET_HIGH_WORD(hy,y);
+  SET_HIGH_WORD(x,(hx&0x7fffffff)|(hy&0x80000000));
+        return x;
+}
+
+double scalbn(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;
+}