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.
59V8_EXPORT_PRIVATE void DoubleToAscii(double v, DtoaMode mode,
60 int requested_digits, Vector<char> buffer,
61 int* sign, int* length, int* point);
62
63} // namespace internal
64} // namespace v8
65
66#endif // V8_DTOA_H_
67