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_DTOA_H_
6#define V8_DTOA_H_
7
8namespace v8 {
9namespace internal {
10
11enum DtoaMode {
12  // Return the shortest correct representation.
13  // For example the output of 0.299999999999999988897 is (the less accurate but
14  // correct) 0.3.
15  DTOA_SHORTEST,
16  // Return a fixed number of digits after the decimal point.
17  // For instance fixed(0.1, 4) becomes 0.1000
18  // If the input number is big, the output will be big.
19  DTOA_FIXED,
20  // Return a fixed number of digits, no matter what the exponent is.
21  DTOA_PRECISION
22};
23
24// The maximal length of digits a double can have in base 10.
25// Note that DoubleToAscii null-terminates its input. So the given buffer should
26// be at least kBase10MaximalLength + 1 characters long.
27const int kBase10MaximalLength = 17;
28
29// Converts the given double 'v' to ASCII.
30// The result should be interpreted as buffer * 10^(point-length).
31//
32// The output depends on the given mode:
33//  - SHORTEST: produce the least amount of digits for which the internal
34//   identity requirement is still satisfied. If the digits are printed
35//   (together with the correct exponent) then reading this number will give
36//   'v' again. The buffer will choose the representation that is closest to
37//   'v'. If there are two at the same distance, than the one farther away
38//   from 0 is chosen (halfway cases - ending with 5 - are rounded up).
39//   In this mode the 'requested_digits' parameter is ignored.
40//  - FIXED: produces digits necessary to print a given number with
41//   'requested_digits' digits after the decimal point. The produced digits
42//   might be too short in which case the caller has to fill the gaps with '0's.
43//   Example: toFixed(0.001, 5) is allowed to return buffer="1", point=-2.
44//   Halfway cases are rounded towards +/-Infinity (away from 0). The call
45//   toFixed(0.15, 2) thus returns buffer="2", point=0.
46//   The returned buffer may contain digits that would be truncated from the
47//   shortest representation of the input.
48//  - PRECISION: produces 'requested_digits' where the first digit is not '0'.
49//   Even though the length of produced digits usually equals
50//   'requested_digits', the function is allowed to return fewer digits, in
51//   which case the caller has to fill the missing digits with '0's.
52//   Halfway cases are again rounded away from 0.
53// 'DoubleToAscii' expects the given buffer to be big enough to hold all digits
54// and a terminating null-character. In SHORTEST-mode it expects a buffer of
55// at least kBase10MaximalLength + 1. Otherwise, the size of the output is
56// limited to requested_digits digits plus the null terminator.
57void DoubleToAscii(double v, DtoaMode mode, int requested_digits,
58                   Vector<char> buffer, int* sign, int* length, int* point);
59
60} }  // namespace v8::internal
61
62#endif  // V8_DTOA_H_
63