1 files changed, 79 insertions, 0 deletions
diff --git a/StdLib/LibC/Math/s_tanh.c b/StdLib/LibC/Math/s_tanh.c
new file mode 100644
index 0000000000..f6e17a7b4f
--- /dev/null
+++ b/StdLib/LibC/Math/s_tanh.c
@@ -0,0 +1,79 @@
+/* @(#)s_tanh.c 5.1 93/09/24 */
+/*
+ * ====================================================
+ * 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  <LibConfig.h>
+#include  <sys/EfiCdefs.h>
+#if defined(LIBM_SCCS) && !defined(lint)
+__RCSID("$NetBSD: s_tanh.c,v 1.10 2002/05/26 22:01:59 wiz Exp $");
+#endif
+
+/* Tanh(x)
+ * Return the Hyperbolic Tangent of x
+ *
+ * Method :
+ *               x    -x
+ *              e  - e
+ *  0. tanh(x) is defined to be -----------
+ *               x    -x
+ *              e  + e
+ *  1. reduce x to non-negative by tanh(-x) = -tanh(x).
+ *  2.  0      <= x <= 2**-55 : tanh(x) := x*(one+x)
+ *                  -t
+ *      2**-55 <  x <=  1     : tanh(x) := -----; t = expm1(-2x)
+ *                 t + 2
+ *                 2
+ *      1      <= x <=  22.0  : tanh(x) := 1-  ----- ; t=expm1(2x)
+ *               t + 2
+ *      22.0   <  x <= INF    : tanh(x) := 1.
+ *
+ * Special cases:
+ *  tanh(NaN) is NaN;
+ *  only tanh(0)=0 is exact for finite argument.
+ */
+
+#include "math.h"
+#include "math_private.h"
+
+static const double one=1.0, two=2.0, tiny = 1.0e-300;
+
+double
+tanh(double x)
+{
+  double t,z;
+  int32_t jx,ix;
+
+    /* High word of |x|. */
+  GET_HIGH_WORD(jx,x);
+  ix = jx&0x7fffffff;
+
+    /* x is INF or NaN */
+  if(ix>=0x7ff00000) {
+      if (jx>=0) return one/x+one;    /* tanh(+-inf)=+-1 */
+      else       return one/x-one;    /* tanh(NaN) = NaN */
+  }
+
+    /* |x| < 22 */
+  if (ix < 0x40360000) {    /* |x|<22 */
+      if (ix<0x3c800000)    /* |x|<2**-55 */
+    return x*(one+x);     /* tanh(small) = small */
+      if (ix>=0x3ff00000) { /* |x|>=1  */
+    t = expm1(two*fabs(x));
+    z = one - two/(t+two);
+      } else {
+          t = expm1(-two*fabs(x));
+          z= -t/(t+two);
+      }
+    /* |x| > 22, return +-1 */
+  } else {
+      z = one - tiny;   /* raised inexact flag */
+  }
+  return (jx>=0)? z: -z;
+}