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