first commit of the new libm!

[musl] / src / math / nextafter.c

diff --git a/src/math/nextafter.c b/src/math/nextafter.c
new file mode 100644 (file)
index 0000000..5e53654
--- /dev/null
+++ b/src/math/nextafter.c
@@ -0,0 +1,79 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/s_nextafter.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.
+ * ====================================================
+ */
+/* IEEE functions
+ *      nextafter(x,y)
+ *      return the next machine floating-point number of x in the
+ *      direction toward y.
+ *   Special cases:
+ */
+
+#include "libm.h"
+
+double nextafter(double x, double y)
+{
+       volatile double t;
+       int32_t hx,hy,ix,iy;
+       uint32_t lx,ly;
+
+       EXTRACT_WORDS(hx, lx, x);
+       EXTRACT_WORDS(hy, ly, y);
+       ix = hx & 0x7fffffff;  /* |x| */
+       iy = hy & 0x7fffffff;  /* |y| */
+
+       if ((ix >= 0x7ff00000 && (ix-0x7ff00000)|lx) != 0 ||   /* x is nan */
+           (iy >= 0x7ff00000 && (iy-0x7ff00000)|ly) != 0)     /* y is nan */
+               return x+y;
+       if (x == y)          /* x == y */
+               return y;
+       if ((ix|lx) == 0) {  /* x == 0 */
+               INSERT_WORDS(x, hy&0x80000000, 1);  /* return +-minsubnormal */
+               /* raise underflow flag */
+               t = x*x;
+               if (t == x)
+                       return t;
+               return x;
+       }
+       if (hx >= 0) {  /* x > 0 */
+               if (hx > hy || (hx == hy && lx > ly)) {  /* x > y, x -= ulp */
+                       if (lx == 0)
+                               hx--;
+                       lx--;
+               } else {                                 /* x < y, x += ulp */
+                       lx++;
+                       if (lx == 0)
+                               hx++;
+               }
+       } else {        /* x < 0 */
+               if (hy >= 0 || hx > hy || (hx == hy && lx > ly)) { /* x < y, x -= ulp */
+                       if (lx == 0)
+                               hx--;
+                       lx--;
+               } else {                                 /* x > y, x += ulp */
+                       lx++;
+                       if (lx == 0)
+                               hx++;
+               }
+       }
+       hy = hx & 0x7ff00000;
+       if (hy >= 0x7ff00000)  /* overflow  */
+               return x+x;
+       if (hy < 0x00100000) { /* underflow */
+               /* raise underflow flag */
+               t = x*x;
+               if (t != x) {
+                       INSERT_WORDS(y, hx, lx);
+                       return y;
+               }
+       }
+       INSERT_WORDS(x, hx, lx);
+       return x;
+}