1 // Copyright 2010 the V8 project authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef V8_BIGNUM_DTOA_H_ 6 #define V8_BIGNUM_DTOA_H_ 7 8 #include "src/vector.h" 9 10 namespace v8 { 11 namespace internal { 12 13 enum BignumDtoaMode { 14 // Return the shortest correct representation. 15 // For example the output of 0.299999999999999988897 is (the less accurate but 16 // correct) 0.3. 17 BIGNUM_DTOA_SHORTEST, 18 // Return a fixed number of digits after the decimal point. 19 // For instance fixed(0.1, 4) becomes 0.1000 20 // If the input number is big, the output will be big. 21 BIGNUM_DTOA_FIXED, 22 // Return a fixed number of digits, no matter what the exponent is. 23 BIGNUM_DTOA_PRECISION 24 }; 25 26 // Converts the given double 'v' to ASCII. 27 // The result should be interpreted as buffer * 10^(point-length). 28 // The buffer will be null-terminated. 29 // 30 // The input v must be > 0 and different from NaN, and Infinity. 31 // 32 // The output depends on the given mode: 33 // - SHORTEST: produce the least amount of digits for which the internal 34 // identity requirement is still satisfied. If the digits are printed 35 // (together with the correct exponent) then reading this number will give 36 // 'v' again. The buffer will choose the representation that is closest to 37 // 'v'. If there are two at the same distance, than the number is round up. 38 // In this mode the 'requested_digits' parameter is ignored. 39 // - FIXED: produces digits necessary to print a given number with 40 // 'requested_digits' digits after the decimal point. The produced digits 41 // might be too short in which case the caller has to fill the gaps with '0's. 42 // Example: toFixed(0.001, 5) is allowed to return buffer="1", point=-2. 43 // Halfway cases are rounded up. The call toFixed(0.15, 2) thus returns 44 // buffer="2", point=0. 45 // Note: the length of the returned buffer has no meaning wrt the significance 46 // of its digits. That is, just because it contains '0's does not mean that 47 // any other digit would not satisfy the internal identity requirement. 48 // - PRECISION: produces 'requested_digits' where the first digit is not '0'. 49 // Even though the length of produced digits usually equals 50 // 'requested_digits', the function is allowed to return fewer digits, in 51 // which case the caller has to fill the missing digits with '0's. 52 // Halfway cases are again rounded up. 53 // 'BignumDtoa' expects the given buffer to be big enough to hold all digits 54 // and a terminating null-character. 55 void BignumDtoa(double v, BignumDtoaMode mode, int requested_digits, 56 Vector<char> buffer, int* length, int* point); 57 58 } // namespace internal 59 } // namespace v8 60 61 #endif // V8_BIGNUM_DTOA_H_ 62
