1// Copyright 2011 the V8 project authors. All rights reserved.
2// Use of this source code is governed by a BSD-style license that can be
3// found in the LICENSE file.
4
5#ifndef V8_FAST_DTOA_H_
6#define V8_FAST_DTOA_H_
7
8namespace v8 {
9namespace internal {
10
11enum FastDtoaMode {
12  // Computes the shortest representation of the given input. The returned
13  // result will be the most accurate number of this length. Longer
14  // representations might be more accurate.
15  FAST_DTOA_SHORTEST,
16  // Computes a representation where the precision (number of digits) is
17  // given as input. The precision is independent of the decimal point.
18  FAST_DTOA_PRECISION
19};
20
21// FastDtoa will produce at most kFastDtoaMaximalLength digits. This does not
22// include the terminating '\0' character.
23const int kFastDtoaMaximalLength = 17;
24
25// Provides a decimal representation of v.
26// The result should be interpreted as buffer * 10^(point - length).
27//
28// Precondition:
29//   * v must be a strictly positive finite double.
30//
31// Returns true if it succeeds, otherwise the result can not be trusted.
32// There will be *length digits inside the buffer followed by a null terminator.
33// If the function returns true and mode equals
34//   - FAST_DTOA_SHORTEST, then
35//     the parameter requested_digits is ignored.
36//     The result satisfies
37//         v == (double) (buffer * 10^(point - length)).
38//     The digits in the buffer are the shortest representation possible. E.g.
39//     if 0.099999999999 and 0.1 represent the same double then "1" is returned
40//     with point = 0.
41//     The last digit will be closest to the actual v. That is, even if several
42//     digits might correctly yield 'v' when read again, the buffer will contain
43//     the one closest to v.
44//   - FAST_DTOA_PRECISION, then
45//     the buffer contains requested_digits digits.
46//     the difference v - (buffer * 10^(point-length)) is closest to zero for
47//     all possible representations of requested_digits digits.
48//     If there are two values that are equally close, then FastDtoa returns
49//     false.
50// For both modes the buffer must be large enough to hold the result.
51bool FastDtoa(double d,
52              FastDtoaMode mode,
53              int requested_digits,
54              Vector<char> buffer,
55              int* length,
56              int* decimal_point);
57
58} }  // namespace v8::internal
59
60#endif  // V8_FAST_DTOA_H_
61