first commit of the new libm!

[musl] / src / math / trunc.c

diff --git a/src/math/trunc.c b/src/math/trunc.c
new file mode 100644 (file)
index 0000000..44b04ec
--- /dev/null
+++ b/src/math/trunc.c
@@ -0,0 +1,63 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/s_trunc.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.
+ * ====================================================
+ */
+/*
+ * trunc(x)
+ * Return x rounded toward 0 to integral value
+ * Method:
+ *      Bit twiddling.
+ * Exception:
+ *      Inexact flag raised if x not equal to trunc(x).
+ */
+
+#include "libm.h"
+
+static const double huge = 1.0e300;
+
+double trunc(double x)
+{
+       int32_t i0,i1,j0;
+       uint32_t i;
+
+       EXTRACT_WORDS(i0, i1, x);
+       j0 = ((i0>>20)&0x7ff) - 0x3ff;
+       if (j0 < 20) {
+               if (j0 < 0) { /* |x|<1, return 0*sign(x) */
+                       /* raise inexact if x != 0 */
+                       if (huge+x > 0.0) {
+                               i0 &= 0x80000000U;
+                               i1 = 0;
+                       }
+               } else {
+                       i = 0x000fffff>>j0;
+                       if (((i0&i)|i1) == 0)
+                               return x; /* x is integral */
+                       /* raise inexact */
+                       if (huge+x > 0.0) {
+                               i0 &= ~i;
+                               i1 = 0;
+                       }
+               }
+       } else if (j0 > 51) {
+               if (j0 == 0x400)
+                       return x + x;  /* inf or NaN */
+               return x;              /* x is integral */
+       } else {
+               i = (uint32_t)0xffffffff>>(j0-20);
+               if ((i1&i) == 0)
+                       return x;      /* x is integral */
+               /* raise inexact */
+               if (huge+x > 0.0)
+                       i1 &= ~i;
+       }
+       INSERT_WORDS(x, i0, i1);
+       return x;
+}