d4b533d41b
R=svenpanne@chromium.org Review URL: https://codereview.chromium.org/259183002 git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@21035 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
63 lines
2.9 KiB
C++
63 lines
2.9 KiB
C++
// Copyright 2011 the V8 project authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef V8_DTOA_H_
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#define V8_DTOA_H_
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namespace v8 {
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namespace internal {
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enum DtoaMode {
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// Return the shortest correct representation.
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// For example the output of 0.299999999999999988897 is (the less accurate but
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// correct) 0.3.
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DTOA_SHORTEST,
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// Return a fixed number of digits after the decimal point.
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// For instance fixed(0.1, 4) becomes 0.1000
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// If the input number is big, the output will be big.
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DTOA_FIXED,
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// Return a fixed number of digits, no matter what the exponent is.
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DTOA_PRECISION
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};
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// The maximal length of digits a double can have in base 10.
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// Note that DoubleToAscii null-terminates its input. So the given buffer should
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// be at least kBase10MaximalLength + 1 characters long.
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const int kBase10MaximalLength = 17;
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// Converts the given double 'v' to ASCII.
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// The result should be interpreted as buffer * 10^(point-length).
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//
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// The output depends on the given mode:
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// - SHORTEST: produce the least amount of digits for which the internal
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// identity requirement is still satisfied. If the digits are printed
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// (together with the correct exponent) then reading this number will give
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// 'v' again. The buffer will choose the representation that is closest to
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// 'v'. If there are two at the same distance, than the one farther away
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// from 0 is chosen (halfway cases - ending with 5 - are rounded up).
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// In this mode the 'requested_digits' parameter is ignored.
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// - FIXED: produces digits necessary to print a given number with
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// 'requested_digits' digits after the decimal point. The produced digits
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// might be too short in which case the caller has to fill the gaps with '0's.
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// Example: toFixed(0.001, 5) is allowed to return buffer="1", point=-2.
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// Halfway cases are rounded towards +/-Infinity (away from 0). The call
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// toFixed(0.15, 2) thus returns buffer="2", point=0.
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// The returned buffer may contain digits that would be truncated from the
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// shortest representation of the input.
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// - PRECISION: produces 'requested_digits' where the first digit is not '0'.
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// Even though the length of produced digits usually equals
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// 'requested_digits', the function is allowed to return fewer digits, in
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// which case the caller has to fill the missing digits with '0's.
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// Halfway cases are again rounded away from 0.
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// 'DoubleToAscii' expects the given buffer to be big enough to hold all digits
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// and a terminating null-character. In SHORTEST-mode it expects a buffer of
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// at least kBase10MaximalLength + 1. Otherwise, the size of the output is
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// limited to requested_digits digits plus the null terminator.
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void DoubleToAscii(double v, DtoaMode mode, int requested_digits,
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Vector<char> buffer, int* sign, int* length, int* point);
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} } // namespace v8::internal
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#endif // V8_DTOA_H_
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