Add double-conversion to third_party (#447)

third_party/double-conversion/fast-dtoa.h

@@ -0,0 +1,88 @@
+// 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 DOUBLE_CONVERSION_FAST_DTOA_H_
+#define DOUBLE_CONVERSION_FAST_DTOA_H_
+
+#include "third_party/double-conversion/utils.h"
+
+namespace double_conversion {
+
+enum FastDtoaMode {
+  // Computes the shortest representation of the given input. The returned
+  // result will be the most accurate number of this length. Longer
+  // representations might be more accurate.
+  FAST_DTOA_SHORTEST,
+  // Same as FAST_DTOA_SHORTEST but for single-precision floats.
+  FAST_DTOA_SHORTEST_SINGLE,
+  // Computes a representation where the precision (number of digits) is
+  // given as input. The precision is independent of the decimal point.
+  FAST_DTOA_PRECISION
+};
+
+// FastDtoa will produce at most kFastDtoaMaximalLength digits. This does not
+// include the terminating '\0' character.
+static const int kFastDtoaMaximalLength = 17;
+// Same for single-precision numbers.
+static const int kFastDtoaMaximalSingleLength = 9;
+
+// Provides a decimal representation of v.
+// The result should be interpreted as buffer * 10^(point - length).
+//
+// Precondition:
+//   * v must be a strictly positive finite double.
+//
+// Returns true if it succeeds, otherwise the result can not be trusted.
+// There will be *length digits inside the buffer followed by a null terminator.
+// If the function returns true and mode equals
+//   - FAST_DTOA_SHORTEST, then
+//     the parameter requested_digits is ignored.
+//     The result satisfies
+//         v == (double) (buffer * 10^(point - length)).
+//     The digits in the buffer are the shortest representation possible. E.g.
+//     if 0.099999999999 and 0.1 represent the same double then "1" is returned
+//     with point = 0.
+//     The last digit will be closest to the actual v. That is, even if several
+//     digits might correctly yield 'v' when read again, the buffer will contain
+//     the one closest to v.
+//   - FAST_DTOA_PRECISION, then
+//     the buffer contains requested_digits digits.
+//     the difference v - (buffer * 10^(point-length)) is closest to zero for
+//     all possible representations of requested_digits digits.
+//     If there are two values that are equally close, then FastDtoa returns
+//     false.
+// For both modes the buffer must be large enough to hold the result.
+bool FastDtoa(double d,
+              FastDtoaMode mode,
+              int requested_digits,
+              Vector<char> buffer,
+              int* length,
+              int* decimal_point);
+
+}  // namespace double_conversion
+
+#endif  // DOUBLE_CONVERSION_FAST_DTOA_H_