From 241d02154216d22a0932d13843f4d76d7412905d Mon Sep 17 00:00:00 2001
From: Rob Norris <rw_norris@hotmail.com>
Date: Tue, 27 May 2014 22:05:08 +0100
Subject: [PATCH] strtod.c from Sanos Operating System Kernel 1.3.4
 (http://www.jbox.dk/sanos)

---
 src/misc/strtod.c | 155 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 155 insertions(+)
 create mode 100644 src/misc/strtod.c

diff --git a/src/misc/strtod.c b/src/misc/strtod.c
new file mode 100644
index 00000000..17936dac
--- /dev/null
+++ b/src/misc/strtod.c
@@ -0,0 +1,155 @@
+//
+// strtod.c
+//
+// Convert string to double 
+//
+// Copyright (C) 2002 Michael Ringgaard. All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions
+// are met:
+// 
+// 1. Redistributions of source code must retain the above copyright 
+//    notice, this list of conditions and the following disclaimer.  
+// 2. Redistributions in binary form must reproduce the above copyright
+//    notice, this list of conditions and the following disclaimer in the
+//    documentation and/or other materials provided with the distribution.  
+// 3. Neither the name of the project nor the names of its contributors
+//    may be used to endorse or promote products derived from this software
+//    without specific prior written permission. 
+// 
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
+// ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+// ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
+// FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+// DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+// OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+// HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+// LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+// OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 
+// SUCH DAMAGE.
+// 
+
+#include <errno.h>
+#include <ctype.h>
+#include <math.h>
+#include <float.h>
+#include <stdlib.h>
+
+double strtod(const char *str, char **endptr) {
+  double number;
+  int exponent;
+  int negative;
+  char *p = (char *) str;
+  double p10;
+  int n;
+  int num_digits;
+  int num_decimals;
+
+  // Skip leading whitespace
+  while (isspace(*p)) p++;
+
+  // Handle optional sign
+  negative = 0;
+  switch (*p) {
+    case '-': negative = 1; // Fall through to increment position
+    case '+': p++;
+  }
+
+  number = 0.;
+  exponent = 0;
+  num_digits = 0;
+  num_decimals = 0;
+
+  // Process string of digits
+  while (isdigit(*p)) {
+    number = number * 10. + (*p - '0');
+    p++;
+    num_digits++;
+  }
+
+  // Process decimal part
+  if (*p == '.') {
+    p++;
+
+    while (isdigit(*p)) {
+      number = number * 10. + (*p - '0');
+      p++;
+      num_digits++;
+      num_decimals++;
+    }
+
+    exponent -= num_decimals;
+  }
+
+  if (num_digits == 0) {
+    errno = ERANGE;
+    return 0.0;
+  }
+
+  // Correct for sign
+  if (negative) number = -number;
+
+  // Process an exponent string
+  if (*p == 'e' || *p == 'E') {
+    // Handle optional sign
+    negative = 0;
+    switch (*++p) {
+      case '-': negative = 1;   // Fall through to increment pos
+      case '+': p++;
+    }
+
+    // Process string of digits
+    n = 0;
+    while (isdigit(*p)) {
+      n = n * 10 + (*p - '0');
+      p++;
+    }
+
+    if (negative) {
+      exponent -= n;
+    } else {
+      exponent += n;
+    }
+  }
+
+  if (exponent < DBL_MIN_EXP  || exponent > DBL_MAX_EXP) {
+    errno = ERANGE;
+    return HUGE_VAL;
+  }
+
+  // Scale the result
+  p10 = 10.;
+  n = exponent;
+  if (n < 0) n = -n;
+  while (n) {
+    if (n & 1) {
+      if (exponent < 0) {
+        number /= p10;
+      } else {
+        number *= p10;
+      }
+    }
+    n >>= 1;
+    p10 *= p10;
+  }
+
+  if (number == HUGE_VAL) errno = ERANGE;
+  if (endptr) *endptr = p;
+
+  return number;
+}
+
+float strtof(const char *str, char **endptr) {
+  return (float) strtod(str, endptr);
+}
+
+
+long double strtold(const char *str, char **endptr) {
+  return strtod(str, endptr);
+}
+
+double atof(const char *str) {
+  return strtod(str, NULL);
+}
-- 
2.39.5