1// Copyright 2011 the V8 project authors. All rights reserved.
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27
28#ifndef V8_DTOA_H_
29#define V8_DTOA_H_
30
31namespace v8 {
32namespace internal {
33
34enum DtoaMode {
35  // Return the shortest correct representation.
36  // For example the output of 0.299999999999999988897 is (the less accurate but
37  // correct) 0.3.
38  DTOA_SHORTEST,
39  // Return a fixed number of digits after the decimal point.
40  // For instance fixed(0.1, 4) becomes 0.1000
41  // If the input number is big, the output will be big.
42  DTOA_FIXED,
43  // Return a fixed number of digits, no matter what the exponent is.
44  DTOA_PRECISION
45};
46
47// The maximal length of digits a double can have in base 10.
48// Note that DoubleToAscii null-terminates its input. So the given buffer should
49// be at least kBase10MaximalLength + 1 characters long.
50const int kBase10MaximalLength = 17;
51
52// Converts the given double 'v' to ASCII.
53// The result should be interpreted as buffer * 10^(point-length).
54//
55// The output depends on the given mode:
56//  - SHORTEST: produce the least amount of digits for which the internal
57//   identity requirement is still satisfied. If the digits are printed
58//   (together with the correct exponent) then reading this number will give
59//   'v' again. The buffer will choose the representation that is closest to
60//   'v'. If there are two at the same distance, than the one farther away
61//   from 0 is chosen (halfway cases - ending with 5 - are rounded up).
62//   In this mode the 'requested_digits' parameter is ignored.
63//  - FIXED: produces digits necessary to print a given number with
64//   'requested_digits' digits after the decimal point. The produced digits
65//   might be too short in which case the caller has to fill the gaps with '0's.
66//   Example: toFixed(0.001, 5) is allowed to return buffer="1", point=-2.
67//   Halfway cases are rounded towards +/-Infinity (away from 0). The call
68//   toFixed(0.15, 2) thus returns buffer="2", point=0.
69//   The returned buffer may contain digits that would be truncated from the
70//   shortest representation of the input.
71//  - PRECISION: produces 'requested_digits' where the first digit is not '0'.
72//   Even though the length of produced digits usually equals
73//   'requested_digits', the function is allowed to return fewer digits, in
74//   which case the caller has to fill the missing digits with '0's.
75//   Halfway cases are again rounded away from 0.
76// 'DoubleToAscii' expects the given buffer to be big enough to hold all digits
77// and a terminating null-character. In SHORTEST-mode it expects a buffer of
78// at least kBase10MaximalLength + 1. Otherwise, the size of the output is
79// limited to requested_digits digits plus the null terminator.
80void DoubleToAscii(double v, DtoaMode mode, int requested_digits,
81                   Vector<char> buffer, int* sign, int* length, int* point);
82
83} }  // namespace v8::internal
84
85#endif  // V8_DTOA_H_
86