1 files changed, 135 insertions, 0 deletions
diff --git a/newlib/libm/mathfp/s_logarithm.c b/newlib/libm/mathfp/s_logarithm.c
new file mode 100644
index 00000000000..ee7c7069ebf
--- /dev/null
+++ b/newlib/libm/mathfp/s_logarithm.c
@@ -0,0 +1,135 @@
+
+/* @(#)z_logarithm.c 1.0 98/08/13 */
+/******************************************************************
+ * The following routines are coded directly from the algorithms
+ * and coefficients given in "Software Manual for the Elementary
+ * Functions" by William J. Cody, Jr. and William Waite, Prentice
+ * Hall, 1980.
+ ******************************************************************/
+
+/*
+FUNCTION
+       <<log>>, <<logf>>, <<log10>>, <<log10f>>, <<logarithm>>, <<logarithmf>>---natural or base 10 logarithms
+
+INDEX
+    log
+INDEX
+    logf
+INDEX
+    log10
+INDEX
+    log10f
+
+ANSI_SYNOPSIS
+       #include <math.h>
+       double log(double <[x]>);
+       float logf(float <[x]>);
+       double log10(double <[x]>);
+       float log10f(float <[x]>);
+
+TRAD_SYNOPSIS
+       #include <math.h>
+       double log(<[x]>);
+       double <[x]>;
+
+       float logf(<[x]>);
+       float <[x]>;
+
+       double log10(<[x]>);
+       double <[x]>;
+
+       float log10f(<[x]>);
+       float <[x]>;
+
+DESCRIPTION
+Return the natural or base 10 logarithm of <[x]>, that is, its logarithm base e
+(where e is the base of the natural system of logarithms, 2.71828@dots{}) or
+base 10.
+<<log>> and <<logf>> are identical save for the return and argument types.
+<<log10>> and <<log10f>> are identical save for the return and argument types.
+
+RETURNS
+Normally, returns the calculated value.  When <[x]> is zero, the
+returned value is <<-HUGE_VAL>> and <<errno>> is set to <<ERANGE>>.
+When <[x]> is negative, the returned value is <<-HUGE_VAL>> and
+<<errno>> is set to <<EDOM>>.  You can control the error behavior via
+<<matherr>>.
+
+PORTABILITY
+<<log>> is ANSI, <<logf>> is an extension.
+<<log10>> is ANSI, <<log10f>> is an extension.
+*/
+
+
+/******************************************************************
+ * Logarithm
+ *
+ * Input:
+ *   x - floating point value
+ *   ten - indicates base ten numbers
+ *
+ * Output:
+ *   logarithm of x
+ *
+ * Description:
+ *   This routine calculates logarithms.
+ *
+ *****************************************************************/
+
+#include "fdlibm.h"
+#include "zmath.h"
+
+#ifndef _DOUBLE_IS_32BITS
+
+static const double a[] = { -0.64124943423745581147e+02,
+                             0.16383943563021534222e+02,
+                            -0.78956112887481257267 };
+static const double b[] = { -0.76949932108494879777e+03,
+                             0.31203222091924532844e+03,
+                            -0.35667977739034646171e+02 };
+static const double C1 =  22713.0 / 32768.0;
+static const double C2 =  1.428606820309417232e-06;
+static const double C3 =  0.43429448190325182765;
+
+double
+_DEFUN (logarithm, (double, int),
+        double x _AND
+        int ten)
+{
+  int N;
+  double f, w, z;
+
+  /* Check for domain error here. */
+  if (x <= 0.0)
+    {
+      errno = ERANGE;
+      return (z_notanum.d);
+    }
+
+  /* Get the exponent and mantissa where x = f * 2^N. */
+  f = frexp (x, &N);
+
+  z = f - 0.5;
+
+  if (f > __SQRT_HALF)
+    z = (z - 0.5) / (f * 0.5 + 0.5);
+  else
+    {
+      N--;
+      z /= (z * 0.5 + 0.5);
+    }
+  w = z * z;
+
+  /* Use Newton's method with 4 terms. */
+  z += z * w * ((a[2] * w + a[1]) * w + a[0]) / (((w + b[2]) * w + b[1]) * w + b[0]);
+
+  if (N != 0)
+    z = (N * C2 + z) + N * C1;
+
+  if (ten)
+    z *= C3;
+
+  return (z);
+}
+
+#endif /* _DOUBLE_IS_32BITS */