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27
28#ifndef DOUBLE_CONVERSION_FAST_DTOA_H_
29#define DOUBLE_CONVERSION_FAST_DTOA_H_
30
31#include <wtf/dtoa/utils.h>
32
33namespace WTF {
34namespace double_conversion {
35
36enum FastDtoaMode {
37 // Computes the shortest representation of the given input. The returned
38 // result will be the most accurate number of this length. Longer
39 // representations might be more accurate.
40 FAST_DTOA_SHORTEST,
41 // Same as FAST_DTOA_SHORTEST but for single-precision floats.
42 FAST_DTOA_SHORTEST_SINGLE,
43 // Computes a representation where the precision (number of digits) is
44 // given as input. The precision is independent of the decimal point.
45 FAST_DTOA_PRECISION
46};
47
48// FastDtoa will produce at most kFastDtoaMaximalLength digits. This does not
49// include the terminating '\0' character.
50static const int kFastDtoaMaximalLength = 17;
51// Same for single-precision numbers.
52static const int kFastDtoaMaximalSingleLength = 9;
53
54// Provides a decimal representation of v.
55// The result should be interpreted as buffer * 10^(point - length).
56//
57// Precondition:
58// * v must be a strictly positive finite double.
59//
60// Returns true if it succeeds, otherwise the result can not be trusted.
61// There will be *length digits inside the buffer followed by a null terminator.
62// If the function returns true and mode equals
63// - FAST_DTOA_SHORTEST, then
64// the parameter requested_digits is ignored.
65// The result satisfies
66// v == (double) (buffer * 10^(point - length)).
67// The digits in the buffer are the shortest representation possible. E.g.
68// if 0.099999999999 and 0.1 represent the same double then "1" is returned
69// with point = 0.
70// The last digit will be closest to the actual v. That is, even if several
71// digits might correctly yield 'v' when read again, the buffer will contain
72// the one closest to v.
73// - FAST_DTOA_PRECISION, then
74// the buffer contains requested_digits digits.
75// the difference v - (buffer * 10^(point-length)) is closest to zero for
76// all possible representations of requested_digits digits.
77// If there are two values that are equally close, then FastDtoa returns
78// false.
79// For both modes the buffer must be large enough to hold the result.
80bool FastDtoa(double d,
81 FastDtoaMode mode,
82 int requested_digits,
83 BufferReference<char> buffer,
84 int* length,
85 int* decimal_point);
86
87} // namespace double_conversion
88} // namespace WTF
89
90#endif // DOUBLE_CONVERSION_FAST_DTOA_H_
91