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      1 // Copyright 2010 the V8 project authors. All rights reserved.
      2 // Redistribution and use in source and binary forms, with or without
      3 // modification, are permitted provided that the following conditions are
      4 // met:
      5 //
      6 //     * Redistributions of source code must retain the above copyright
      7 //       notice, this list of conditions and the following disclaimer.
      8 //     * Redistributions in binary form must reproduce the above
      9 //       copyright notice, this list of conditions and the following
     10 //       disclaimer in the documentation and/or other materials provided
     11 //       with the distribution.
     12 //     * Neither the name of Google Inc. nor the names of its
     13 //       contributors may be used to endorse or promote products derived
     14 //       from this software without specific prior written permission.
     15 //
     16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     27 
     28 #ifndef V8_BIGNUM_DTOA_H_
     29 #define V8_BIGNUM_DTOA_H_
     30 
     31 namespace v8 {
     32 namespace internal {
     33 
     34 enum 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.
     76 void 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