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