android / platform / external / chromium_org / v8 / baf4b7536eee2d8fefabdab9be2901c4b04f1c85 / . / src / dtoa.h

// Copyright 2011 the V8 project authors. All rights reserved. | |

// Use of this source code is governed by a BSD-style license that can be | |

// found in the LICENSE file. | |

#ifndef V8_DTOA_H_ | |

#define V8_DTOA_H_ | |

namespace v8 { | |

namespace internal { | |

enum DtoaMode { | |

// Return the shortest correct representation. | |

// For example the output of 0.299999999999999988897 is (the less accurate but | |

// correct) 0.3. | |

DTOA_SHORTEST, | |

// Return a fixed number of digits after the decimal point. | |

// For instance fixed(0.1, 4) becomes 0.1000 | |

// If the input number is big, the output will be big. | |

DTOA_FIXED, | |

// Return a fixed number of digits, no matter what the exponent is. | |

DTOA_PRECISION | |

}; | |

// The maximal length of digits a double can have in base 10. | |

// Note that DoubleToAscii null-terminates its input. So the given buffer should | |

// be at least kBase10MaximalLength + 1 characters long. | |

const int kBase10MaximalLength = 17; | |

// Converts the given double 'v' to ASCII. | |

// The result should be interpreted as buffer * 10^(point-length). | |

// | |

// The output depends on the given mode: | |

// - SHORTEST: produce the least amount of digits for which the internal | |

// identity requirement is still satisfied. If the digits are printed | |

// (together with the correct exponent) then reading this number will give | |

// 'v' again. The buffer will choose the representation that is closest to | |

// 'v'. If there are two at the same distance, than the one farther away | |

// from 0 is chosen (halfway cases - ending with 5 - are rounded up). | |

// In this mode the 'requested_digits' parameter is ignored. | |

// - FIXED: produces digits necessary to print a given number with | |

// 'requested_digits' digits after the decimal point. The produced digits | |

// might be too short in which case the caller has to fill the gaps with '0's. | |

// Example: toFixed(0.001, 5) is allowed to return buffer="1", point=-2. | |

// Halfway cases are rounded towards +/-Infinity (away from 0). The call | |

// toFixed(0.15, 2) thus returns buffer="2", point=0. | |

// The returned buffer may contain digits that would be truncated from the | |

// shortest representation of the input. | |

// - PRECISION: produces 'requested_digits' where the first digit is not '0'. | |

// Even though the length of produced digits usually equals | |

// 'requested_digits', the function is allowed to return fewer digits, in | |

// which case the caller has to fill the missing digits with '0's. | |

// Halfway cases are again rounded away from 0. | |

// 'DoubleToAscii' expects the given buffer to be big enough to hold all digits | |

// and a terminating null-character. In SHORTEST-mode it expects a buffer of | |

// at least kBase10MaximalLength + 1. Otherwise, the size of the output is | |

// limited to requested_digits digits plus the null terminator. | |

void DoubleToAscii(double v, DtoaMode mode, int requested_digits, | |

Vector<char> buffer, int* sign, int* length, int* point); | |

} } // namespace v8::internal | |

#endif // V8_DTOA_H_ |