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
8#include "src/vector.h"
9
10namespace v8 {
11namespace internal {
12
13enum DtoaMode {
14  // Return the shortest correct representation.
15  // For example the output of 0.299999999999999988897 is (the less accurate but
16  // correct) 0.3.
17  DTOA_SHORTEST,
18  // Return a fixed number of digits after the decimal point.
19  // For instance fixed(0.1, 4) becomes 0.1000
20  // If the input number is big, the output will be big.
21  DTOA_FIXED,
22  // Return a fixed number of digits, no matter what the exponent is.
23  DTOA_PRECISION
24};
25
26// The maximal length of digits a double can have in base 10.
27// Note that DoubleToAscii null-terminates its input. So the given buffer should
28// be at least kBase10MaximalLength + 1 characters long.
29const int kBase10MaximalLength = 17;
30
31// Converts the given double 'v' to ASCII.
32// The result should be interpreted as buffer * 10^(point-length).
33//
34// The output depends on the given mode:
35//  - SHORTEST: produce the least amount of digits for which the internal
36//   identity requirement is still satisfied. If the digits are printed
37//   (together with the correct exponent) then reading this number will give
38//   'v' again. The buffer will choose the representation that is closest to
39//   'v'. If there are two at the same distance, than the one farther away
40//   from 0 is chosen (halfway cases - ending with 5 - are rounded up).
41//   In this mode the 'requested_digits' parameter is ignored.
42//  - FIXED: produces digits necessary to print a given number with
43//   'requested_digits' digits after the decimal point. The produced digits
44//   might be too short in which case the caller has to fill the gaps with '0's.
45//   Example: toFixed(0.001, 5) is allowed to return buffer="1", point=-2.
46//   Halfway cases are rounded towards +/-Infinity (away from 0). The call
47//   toFixed(0.15, 2) thus returns buffer="2", point=0.
48//   The returned buffer may contain digits that would be truncated from the
49//   shortest representation of the input.
50//  - PRECISION: produces 'requested_digits' where the first digit is not '0'.
51//   Even though the length of produced digits usually equals
52//   'requested_digits', the function is allowed to return fewer digits, in
53//   which case the caller has to fill the missing digits with '0's.
54//   Halfway cases are again rounded away from 0.
55// 'DoubleToAscii' expects the given buffer to be big enough to hold all digits
56// and a terminating null-character. In SHORTEST-mode it expects a buffer of
57// at least kBase10MaximalLength + 1. Otherwise, the size of the output is
58// limited to requested_digits digits plus the null terminator.
59void DoubleToAscii(double v, DtoaMode mode, int requested_digits,
60                   Vector<char> buffer, int* sign, int* length, int* point);
61
62}  // namespace internal
63}  // namespace v8
64
65#endif  // V8_DTOA_H_
66