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fast-dtoa.h
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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 
33 #include "pxr/pxr.h"
34 
35 PXR_NAMESPACE_OPEN_SCOPE
36 
37 namespace pxr_double_conversion {
38 
39 enum FastDtoaMode {
40  // Computes the shortest representation of the given input. The returned
41  // result will be the most accurate number of this length. Longer
42  // representations might be more accurate.
43  FAST_DTOA_SHORTEST,
44  // Same as FAST_DTOA_SHORTEST but for single-precision floats.
45  FAST_DTOA_SHORTEST_SINGLE,
46  // Computes a representation where the precision (number of digits) is
47  // given as input. The precision is independent of the decimal point.
48  FAST_DTOA_PRECISION
49 };
50 
51 // FastDtoa will produce at most kFastDtoaMaximalLength digits. This does not
52 // include the terminating '\0' character.
53 static const int kFastDtoaMaximalLength = 17;
54 // Same for single-precision numbers.
55 static const int kFastDtoaMaximalSingleLength = 9;
56 
57 // Provides a decimal representation of v.
58 // The result should be interpreted as buffer * 10^(point - length).
59 //
60 // Precondition:
61 // * v must be a strictly positive finite double.
62 //
63 // Returns true if it succeeds, otherwise the result can not be trusted.
64 // There will be *length digits inside the buffer followed by a null terminator.
65 // If the function returns true and mode equals
66 // - FAST_DTOA_SHORTEST, then
67 // the parameter requested_digits is ignored.
68 // The result satisfies
69 // v == (double) (buffer * 10^(point - length)).
70 // The digits in the buffer are the shortest representation possible. E.g.
71 // if 0.099999999999 and 0.1 represent the same double then "1" is returned
72 // with point = 0.
73 // The last digit will be closest to the actual v. That is, even if several
74 // digits might correctly yield 'v' when read again, the buffer will contain
75 // the one closest to v.
76 // - FAST_DTOA_PRECISION, then
77 // the buffer contains requested_digits digits.
78 // the difference v - (buffer * 10^(point-length)) is closest to zero for
79 // all possible representations of requested_digits digits.
80 // If there are two values that are equally close, then FastDtoa returns
81 // false.
82 // For both modes the buffer must be large enough to hold the result.
83 bool FastDtoa(double d,
84  FastDtoaMode mode,
85  int requested_digits,
86  Vector<char> buffer,
87  int* length,
88  int* decimal_point);
89 
90 } // namespace pxr_double_conversion
91 
92 PXR_NAMESPACE_CLOSE_SCOPE
93 
94 #endif // DOUBLE_CONVERSION_FAST_DTOA_H_