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63 lines
2.4 KiB
63 lines
2.4 KiB
// 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_FAST_DTOA_H_
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#define V8_FAST_DTOA_H_
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#include "src/vector.h"
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namespace v8 {
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namespace internal {
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enum FastDtoaMode {
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// Computes the shortest representation of the given input. The returned
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// result will be the most accurate number of this length. Longer
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// representations might be more accurate.
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FAST_DTOA_SHORTEST,
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// Computes a representation where the precision (number of digits) is
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// given as input. The precision is independent of the decimal point.
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FAST_DTOA_PRECISION
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};
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// FastDtoa will produce at most kFastDtoaMaximalLength digits. This does not
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// include the terminating '\0' character.
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const int kFastDtoaMaximalLength = 17;
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// Provides a decimal representation of v.
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// The result should be interpreted as buffer * 10^(point - length).
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//
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// Precondition:
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// * v must be a strictly positive finite double.
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//
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// Returns true if it succeeds, otherwise the result can not be trusted.
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// There will be *length digits inside the buffer followed by a null terminator.
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// If the function returns true and mode equals
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// - FAST_DTOA_SHORTEST, then
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// the parameter requested_digits is ignored.
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// The result satisfies
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// v == (double) (buffer * 10^(point - length)).
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// The digits in the buffer are the shortest representation possible. E.g.
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// if 0.099999999999 and 0.1 represent the same double then "1" is returned
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// with point = 0.
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// The last digit will be closest to the actual v. That is, even if several
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// digits might correctly yield 'v' when read again, the buffer will contain
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// the one closest to v.
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// - FAST_DTOA_PRECISION, then
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// the buffer contains requested_digits digits.
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// the difference v - (buffer * 10^(point-length)) is closest to zero for
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// all possible representations of requested_digits digits.
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// If there are two values that are equally close, then FastDtoa returns
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// false.
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// For both modes the buffer must be large enough to hold the result.
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bool FastDtoa(double d,
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FastDtoaMode mode,
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int requested_digits,
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Vector<char> buffer,
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int* length,
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int* decimal_point);
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} // namespace internal
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} // namespace v8
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#endif // V8_FAST_DTOA_H_
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