first commit of the new libm!

[musl] / src / math / nexttoward.c

diff --git a/src/math/nexttoward.c b/src/math/nexttoward.c
new file mode 100644 (file)
index 0000000..5e12c48
--- /dev/null
+++ b/src/math/nexttoward.c
@@ -0,0 +1,67 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/s_nexttoward.c */
+/*
+ * ====================================================
+ * 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 "libm.h"
+#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
+double nexttoward(double x, long double y)
+{
+       return nextafter(x, y);
+}
+#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
+double nexttoward(double x, long double y)
+{
+       union IEEEl2bits uy;
+       volatile double t;
+       int32_t hx,ix;
+       uint32_t lx;
+
+       EXTRACT_WORDS(hx, lx, x);
+       ix = hx & 0x7fffffff;
+       uy.e = y;
+
+       if ((ix >= 0x7ff00000 && ((ix-0x7ff00000)|lx) != 0) ||
+           (uy.bits.exp == 0x7fff && ((uy.bits.manh&~LDBL_NBIT)|uy.bits.manl) != 0))
+               return x + y;  /* x or y is nan */
+       if (x == y)
+               return (double)y;
+       if (x == 0.0) {
+               INSERT_WORDS(x, uy.bits.sign<<31, 1);  /* return +-minsubnormal */
+               /* raise underflow */
+               t = x * x;
+               if (t == x)
+                       return t;
+               return x;
+       }
+       if (hx > 0.0 ^ x < y) {  /* x -= ulp */
+               if (lx == 0)
+                       hx--;
+               lx--;
+       } else {                 /* x += ulp */
+               lx++;
+               if (lx == 0)
+                       hx++;
+       }
+       ix = hx & 0x7ff00000;
+       if (ix >= 0x7ff00000)   /* overflow  */
+               return x + x;
+       if (ix < 0x00100000) {  /* underflow */
+               /* raise underflow flag */
+               t = x * x;
+               if (t != x) {
+                       INSERT_WORDS(x, hx, lx);
+                       return x;
+               }
+       }
+       INSERT_WORDS(x, hx, lx);
+       return x;
+}
+#endif