bignum-dtoa.h 4.04 KB
Newer Older
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46
// Copyright 2010 the V8 project authors. All rights reserved.
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions are
// met:
//
//     * Redistributions of source code must retain the above copyright
//       notice, this list of conditions and the following disclaimer.
//     * Redistributions in binary form must reproduce the above
//       copyright notice, this list of conditions and the following
//       disclaimer in the documentation and/or other materials provided
//       with the distribution.
//     * Neither the name of Google Inc. nor the names of its
//       contributors may be used to endorse or promote products derived
//       from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#ifndef V8_BIGNUM_DTOA_H_
#define V8_BIGNUM_DTOA_H_

namespace v8 {
namespace internal {

enum BignumDtoaMode {
  // Return the shortest correct representation.
  // For example the output of 0.299999999999999988897 is (the less accurate but
  // correct) 0.3.
  BIGNUM_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.
  BIGNUM_DTOA_FIXED,
  // Return a fixed number of digits, no matter what the exponent is.
  BIGNUM_DTOA_PRECISION
};

47
// Converts the given double 'v' to ASCII.
48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81
// The result should be interpreted as buffer * 10^(point-length).
// The buffer will be null-terminated.
//
// The input v must be > 0 and different from NaN, and Infinity.
//
// 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 number is round 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 up. The call toFixed(0.15, 2) thus returns
//     buffer="2", point=0.
//   Note: the length of the returned buffer has no meaning wrt the significance
//   of its digits. That is, just because it contains '0's does not mean that
//   any other digit would not satisfy the internal identity requirement.
//  - 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 up.
// 'BignumDtoa' expects the given buffer to be big enough to hold all digits
// and a terminating null-character.
void BignumDtoa(double v, BignumDtoaMode mode, int requested_digits,
                Vector<char> buffer, int* length, int* point);

} }  // namespace v8::internal

#endif  // V8_BIGNUM_DTOA_H_