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e2e17c3f26
This allows JSON parsing to work on individual chunks of source instead of collecting and concatenating all the parts before parsing. This is made in anticipation of having a UTF-8 version that parses directly on the input codes, without creating a String first. R=sgjesse@google.com Review URL: https://codereview.chromium.org//649113005 git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart@41311 260f80e4-7a28-3924-810f-c04153c831b5
114 lines
3.6 KiB
Dart
114 lines
3.6 KiB
Dart
// Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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// Dart core library.
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// VM implementation of double.
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patch class double {
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static double _nativeParse(String str,
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int start, int end) native "Double_parse";
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static double _tryParseDouble(var str, var start, var end) {
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assert(start < end);
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const int _DOT = 0x2e; // '.'
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const int _ZERO = 0x30; // '0'
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const int _MINUS = 0x2d; // '-'
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const int _N = 0x4e; // 'N'
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const int _a = 0x61; // 'a'
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const int _I = 0x49; // 'I'
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const int _e = 0x65; // 'e'
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int exponent = 0;
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// Set to non-zero if a digit is seen. Avoids accepting ".".
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bool digitsSeen = false;
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// Added to exponent for each digit. Set to -1 when seeing '.'.
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int exponentDelta = 0;
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double doubleValue = 0.0;
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double sign = 1.0;
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int firstChar = str.codeUnitAt(start);
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if (firstChar == _MINUS) {
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sign = -1.0;
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start++;
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if (start == end) return null;
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firstChar = str.codeUnitAt(start);
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}
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if (firstChar == _I) {
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if (end == start + 8 && str.startsWith("nfinity", start + 1)) {
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return sign * double.INFINITY;
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}
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return null;
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}
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if (firstChar == _N) {
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if (end == start + 3 &&
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str.codeUnitAt(start + 1) == _a &&
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str.codeUnitAt(start + 2) == _N) {
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return double.NAN;
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}
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return null;
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}
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int firstDigit = firstChar ^ _ZERO;
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if (firstDigit <= 9) {
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start++;
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doubleValue = firstDigit.toDouble();
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digitsSeen = true;
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}
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for (int i = start; i < end; i++) {
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int c = str.codeUnitAt(i);
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int digit = c ^ _ZERO; // '0'-'9' characters are now 0-9 integers.
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if (digit <= 9) {
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doubleValue = 10.0 * doubleValue + digit;
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// Doubles at or above this value (2**53) might have lost precission.
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const double MAX_EXACT_DOUBLE = 9007199254740992.0;
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if (doubleValue >= MAX_EXACT_DOUBLE) return null;
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exponent += exponentDelta;
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digitsSeen = true;
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} else if (c == _DOT && exponentDelta == 0) {
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exponentDelta = -1;
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} else if ((c | 0x20) == _e) {
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i++;
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if (i == end) return null;
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// int._tryParseSmi treats its end argument as inclusive.
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int expPart = int._tryParseSmi(str, i, end - 1);
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if (expPart == null) return null;
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exponent += expPart;
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break;
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} else {
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return null;
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}
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}
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if (!digitsSeen) return null; // No digits.
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if (exponent == 0) return sign * doubleValue;
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const P10 = POWERS_OF_TEN; // From shared library
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if (exponent < 0) {
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int negExponent = -exponent;
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if (negExponent >= P10.length) return null;
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return sign * (doubleValue / P10[negExponent]);
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}
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if (exponent >= P10.length) return null;
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return sign * (doubleValue * P10[exponent]);
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}
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static double _parse(var str) {
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int len = str.length;
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int start = str._firstNonWhitespace();
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if (start == len) return null; // All whitespace.
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int end = str._lastNonWhitespace() + 1;
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assert(start < end);
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var result = _tryParseDouble(str, start, end);
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if (result != null) return result;
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return _nativeParse(str, start, end);
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}
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/* patch */ static double parse(String str,
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[double onError(String str)]) {
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var result = _parse(str);
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if (result == null) {
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if (onError == null) throw new FormatException("Invalid double", str);
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return onError(str);
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}
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return result;
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}
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}
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