Provide (non Gay) dtoa for fixed notation.

src/dtoa.h

Index: src/dtoa.h
===================================================================
--- src/dtoa.h	(revision 0)
+++ src/dtoa.h	(revision 0)
@@ -0,0 +1,81 @@
+// Copyright 2010 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * 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.
+//     * Neither the name of Google Inc. 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.
+
+#ifndef V8_DTOA_H_
+#define V8_DTOA_H_
+
+namespace v8 {
+namespace internal {
+
+enum DtoaMode {
+  // 0.9999999999999999 becomes 0.1
+  DTOA_SHORTEST,
+  // Fixed number of digits after the decimal point.
+  // For instance fixed(0.1, 4) becomes 0.1000
+  // If the input number is big, the output will be big.
+  DTOA_FIXED,
+  // Fixed number of digits (independent of the decimal point).
+  DTOA_PRECISION
+};
+
+// The maximal length of digits a double can have in base 10.
+// Note that DoubleToAscii null-terminates its input. So the given buffer should
+// be at least kBase10MaximalLength + 1 characters long.
+static const int kBase10MaximalLength = 17;
+
+// Converts the given double 'v' to ascii.
+// The result should be interpreted as buffer * 10^(point-length).
+//
+// The output depends on the given mode:
+//  - SHORTEST: produce the least amount of digits for which the internal
+//   identity requirement is still satisfied. If the digits are printed
+//   (together with the correct exponent) then reading this number will give
+//   'v' again. The buffer will choose the representation that is closest to
+//   'v'. If there are two at the same distance, than the one farther away
+//   from 0 is chosen (halfway cases - ending with 5 - are rounded up).
+//   In this mode the 'requested_digits' parameter is ignored.
+//  - FIXED: produces digits necessary to print a given number with
+//   'requested_digits' digits after the decimal point. The produced digits
+//   might be too short in which case the caller has to fill the gaps with '0's.
+//   Example: toFixed(0.001, 5) is allowed to return buffer="1", point=-2.
+//   Halfway cases are rounded towards +/-Infinity (away from 0). The call
+//   toFixed(0.15, 2) thus returns buffer="2", point=0.
+//   The returned buffer may contain digits that would be truncated from the
+//   shortest representation of the input.
+//  - PRECISION: produces 'requested_digits' where the first digit is not '0'.
+//   Even though the length of produced digits usually equals
+//   'requested_digits', the function is allowed to return fewer digits, in
+//   which case the caller has to fill the missing digits with '0's.
+//   Halfway cases are again rounded away from 0.
+// 'DoubleToAscii' expects the given buffer to be big enough to hold all digits
+// and a terminating null-character.
+bool DoubleToAscii(double v, DtoaMode mode, int requested_digits,
+                   Vector<char> buffer, int* sign, int* length, int* point);
+
+} }  // namespace v8::internal
+
+#endif  // V8_DTOA_H_