1 files changed, 56 insertions, 0 deletions
diff --git a/src/math/asinh.c b/src/math/asinh.c
new file mode 100644
index 00000000..92aa9446
--- /dev/null
+++ b/src/math/asinh.c
@@ -0,0 +1,56 @@
+/* origin: FreeBSD /usr/src/lib/msun/src/s_asinh.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.
+ * ====================================================
+ */
+/* asinh(x)
+ * Method :
+ *      Based on
+ *              asinh(x) = sign(x) * log [ |x| + sqrt(x*x+1) ]
+ *      we have
+ *      asinh(x) := x  if  1+x*x=1,
+ *               := sign(x)*(log(x)+ln2)) for large |x|, else
+ *               := sign(x)*log(2|x|+1/(|x|+sqrt(x*x+1))) if|x|>2, else
+ *               := sign(x)*log1p(|x| + x^2/(1 + sqrt(1+x^2)))
+ */
+
+#include "libm.h"
+
+static const double
+one = 1.00000000000000000000e+00, /* 0x3FF00000, 0x00000000 */
+ln2 = 6.93147180559945286227e-01, /* 0x3FE62E42, 0xFEFA39EF */
+huge= 1.00000000000000000000e+300;
+
+double asinh(double x)
+{
+	double t,w;
+	int32_t hx,ix;
+
+	GET_HIGH_WORD(hx, x);
+	ix = hx & 0x7fffffff;
+	if (ix >= 0x7ff00000)   /* x is inf or NaN */
+		return x+x;
+	if (ix < 0x3e300000) {  /* |x| < 2**-28 */
+		/* return x inexact except 0 */
+		if (huge+x > one)
+			return x;
+	}
+	if (ix > 0x41b00000) {  /* |x| > 2**28 */
+		w = log(fabs(x)) + ln2;
+	} else if (ix > 0x40000000) {  /* 2**28 > |x| > 2.0 */
+		t = fabs(x);
+		w = log(2.0*t + one/(sqrt(x*x+one)+t));
+	} else {                /* 2.0 > |x| > 2**-28 */
+		t = x*x;
+		w =log1p(fabs(x) + t/(one+sqrt(one+t)));
+	}
+	if (hx > 0)
+		return w;
+	return -w;
+}