Still trying to recover directory contents

git-svn-id: svn://svn.code.sf.net/p/nuttx/code/trunk@5330 42af7a65-404d-4744-a932-0658087f49c3

1 files changed, 103 insertions, 0 deletions

diff --git a/nuttx/libc/math/lib_libexpi.c b/nuttx/libc/math/lib_libexpi.c
new file mode 100644
index 000000000..1ec947a71
--- /dev/null
+++ b/nuttx/libc/math/lib_libexpi.c
@@ -0,0 +1,103 @@
+/************************************************************************
+ * lib/math/lib_libexpi.c
+ *
+ * This file is a part of NuttX:
+ *
+ *   Copyright (C) 2012 Gregory Nutt. All rights reserved.
+ *   Ported by: Darcy Gong
+ *
+ * It derives from the Rhombs OS math library by Nick Johnson which has
+ * a compatibile, MIT-style license:
+ *
+ * Copyright (C) 2009-2011 Nick Johnson <nickbjohnson4224 at gmail.com>
+ * 
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ ************************************************************************/
+
+/************************************************************************
+ * Included Files
+ ************************************************************************/
+
+#include <nuttx/config.h>
+#include <nuttx/compiler.h>
+
+#include <sys/types.h>
+#include <math.h>
+
+/************************************************************************
+ * Public Functions
+ ************************************************************************/
+
+/************************************************************************
+ * Pre-processor Definitions
+ ************************************************************************/
+
+#define M_E2    (M_E * M_E)
+#define M_E4    (M_E2 * M_E2)
+#define M_E8    (M_E4 * M_E4)
+#define M_E16   (M_E8 * M_E8)
+#define M_E32   (M_E16 * M_E16)
+#define M_E64   (M_E32 * M_E32)
+#define M_E128  (M_E64 * M_E64)
+#define M_E256  (M_E128 * M_E128)
+#define M_E512  (M_E256 * M_E256)
+#define M_E1024 (M_E512 * M_E512)
+
+/************************************************************************
+ * Private Data
+ ************************************************************************/
+
+static double _expi_square_tbl[11] =
+{
+  M_E,                          // e^1
+  M_E2,                         // e^2
+  M_E4,                         // e^4
+  M_E8,                         // e^8
+  M_E16,                        // e^16
+  M_E32,                        // e^32
+  M_E64,                        // e^64
+  M_E128,                       // e^128
+  M_E256,                       // e^256
+  M_E512,                       // e^512
+  M_E1024,                      // e^1024
+};
+
+/************************************************************************
+ * Public Functions
+ ************************************************************************/
+
+double lib_expi(size_t n)
+{
+  size_t i;
+  double val;
+
+  if (n > 1024)
+    {
+      return INFINITY;
+    }
+
+  val = 1.0;
+
+  for (i = 0; n; i++)
+    {
+      if (n & (1 << i))
+        {
+          n   &= ~(1 << i);
+          val *= _expi_square_tbl[i];
+        }
+    }
+
+  return val;
+}
+