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27
28#ifndef V8_BIGNUM_DTOA_H_
29#define V8_BIGNUM_DTOA_H_
30
31namespace v8 {
32namespace internal {
33
34enum BignumDtoaMode {
35  // Return the shortest correct representation.
36  // For example the output of 0.299999999999999988897 is (the less accurate but
37  // correct) 0.3.
38  BIGNUM_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  BIGNUM_DTOA_FIXED,
43  // Return a fixed number of digits, no matter what the exponent is.
44  BIGNUM_DTOA_PRECISION
45};
46
47// Converts the given double 'v' to ASCII.
48// The result should be interpreted as buffer * 10^(point-length).
49// The buffer will be null-terminated.
50//
51// The input v must be > 0 and different from NaN, and Infinity.
52//
53// The output depends on the given mode:
54//  - SHORTEST: produce the least amount of digits for which the internal
55//   identity requirement is still satisfied. If the digits are printed
56//   (together with the correct exponent) then reading this number will give
57//   'v' again. The buffer will choose the representation that is closest to
58//   'v'. If there are two at the same distance, than the number is round up.
59//   In this mode the 'requested_digits' parameter is ignored.
60//  - FIXED: produces digits necessary to print a given number with
61//   'requested_digits' digits after the decimal point. The produced digits
62//   might be too short in which case the caller has to fill the gaps with '0's.
63//   Example: toFixed(0.001, 5) is allowed to return buffer="1", point=-2.
64//   Halfway cases are rounded up. The call toFixed(0.15, 2) thus returns
65//     buffer="2", point=0.
66//   Note: the length of the returned buffer has no meaning wrt the significance
67//   of its digits. That is, just because it contains '0's does not mean that
68//   any other digit would not satisfy the internal identity requirement.
69//  - PRECISION: produces 'requested_digits' where the first digit is not '0'.
70//   Even though the length of produced digits usually equals
71//   'requested_digits', the function is allowed to return fewer digits, in
72//   which case the caller has to fill the missing digits with '0's.
73//   Halfway cases are again rounded up.
74// 'BignumDtoa' expects the given buffer to be big enough to hold all digits
75// and a terminating null-character.
76void BignumDtoa(double v, BignumDtoaMode mode, int requested_digits,
77                Vector<char> buffer, int* length, int* point);
78
79} }  // namespace v8::internal
80
81#endif  // V8_BIGNUM_DTOA_H_
82