| // Copyright (c) 2016, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| /// Decode a lax JSON encoded text, that is, JSON with Dart-like comments and |
| /// trailing commas. |
| /// |
| /// This is used together with `load.dart` and `save.dart` to allow for an easy |
| /// editing of a human-readable source-map file. |
| |
| library lazon; |
| |
| decode(String text) { |
| return new _Decoder(text)._decode(); |
| } |
| |
| class _Decoder { |
| static final int LF = '\n'.codeUnits.single; |
| static final int CR = '\r'.codeUnits.single; |
| static final int BACKSPACE = '\b'.codeUnits.single; |
| static final int FORMFEED = '\f'.codeUnits.single; |
| static final int TAB = '\t'.codeUnits.single; |
| static final int SPACE = ' '.codeUnits.single; |
| static final int SLASH = '/'.codeUnits.single; |
| static final int STAR = '*'.codeUnits.single; |
| static final int QUOTE = '"'.codeUnits.single; |
| static final int BACKSLASH = '\\'.codeUnits.single; |
| static final int COMMA = ','.codeUnits.single; |
| static final int COLON = ':'.codeUnits.single; |
| static final int LEFT_BRACE = '{'.codeUnits.single; |
| static final int RIGHT_BRACE = '}'.codeUnits.single; |
| static final int LEFT_BRACKET = '['.codeUnits.single; |
| static final int RIGHT_BRACKET = ']'.codeUnits.single; |
| static final int T = 't'.codeUnits.single; |
| static final List<int> TRUE = 'true'.codeUnits; |
| static final int F = 'f'.codeUnits.single; |
| static final List<int> FALSE = 'false'.codeUnits; |
| static final int N = 'n'.codeUnits.single; |
| static final List<int> NULL = 'null'.codeUnits; |
| static final int _0 = '0'.codeUnits.single; |
| static final int _9 = '9'.codeUnits.single; |
| static final int B = 'b'.codeUnits.single; |
| static final int R = 'r'.codeUnits.single; |
| static final int U = 'u'.codeUnits.single; |
| |
| final List<int> codeUnits; |
| final int length; |
| int position = 0; |
| |
| _Decoder(String text) |
| : codeUnits = text.codeUnits, |
| length = text.length; |
| |
| _decode() { |
| var result = _decodeValue(); |
| _trimWhitespace(); |
| if (position != codeUnits.length) { |
| throw new ArgumentError("Unexpected trailing text: " |
| "'${new String.fromCharCodes(codeUnits, position)}'."); |
| } |
| return result; |
| } |
| |
| _decodeValue() { |
| var result; |
| _trimWhitespace(); |
| if (position < codeUnits.length) { |
| int codeUnit = codeUnits[position]; |
| if (codeUnit == QUOTE) { |
| result = _decodeString(); |
| } else if (codeUnit == LEFT_BRACE) { |
| result = _decodeMap(); |
| } else if (codeUnit == LEFT_BRACKET) { |
| result = _decodeList(); |
| } else if (codeUnit == T) { |
| result = _decodeTrue(); |
| } else if (codeUnit == F) { |
| result = _decodeFalse(); |
| } else if (codeUnit == N) { |
| result = _decodeNull(); |
| } else { |
| result = _decodeNumber(); |
| } |
| } else { |
| throw new ArgumentError("No value found in text: " |
| "'${new String.fromCharCodes(codeUnits, 0)}'."); |
| } |
| return result; |
| } |
| |
| void _trimWhitespace() { |
| OUTER: |
| while (position < codeUnits.length) { |
| int codeUnit = codeUnits[position]; |
| if (codeUnit == SLASH) { |
| if (position + 1 < codeUnits.length) { |
| int nextCodeUnit = codeUnits[position + 1]; |
| if (nextCodeUnit == SLASH) { |
| position += 2; |
| while (position < codeUnits.length) { |
| codeUnit = codeUnits[position]; |
| if (codeUnit == LF || codeUnit == CR) { |
| continue OUTER; |
| } |
| position++; |
| } |
| } else if (nextCodeUnit == STAR) { |
| position += 2; |
| while (position < codeUnits.length) { |
| codeUnit = codeUnits[position]; |
| if (codeUnit == STAR && |
| position + 1 < codeUnits.length && |
| codeUnits[position + 1] == SLASH) { |
| position += 2; |
| continue OUTER; |
| } |
| position++; |
| } |
| } |
| } |
| break; |
| } else if (codeUnit == LF || |
| codeUnit == CR || |
| codeUnit == TAB || |
| codeUnit == SPACE) { |
| position++; |
| } else { |
| break; |
| } |
| } |
| } |
| |
| String _decodeString() { |
| int codeUnit = codeUnits[position]; |
| if (codeUnit != QUOTE) { |
| _fail(); |
| } |
| position++; |
| List<int> charCodes = <int>[]; |
| while (position < length) { |
| codeUnit = codeUnits[position]; |
| if (codeUnit == QUOTE) { |
| break; |
| } else if (codeUnit == BACKSLASH) { |
| if (position + 1 >= length) { |
| _fail(); |
| } |
| codeUnit = codeUnits[++position]; |
| if (codeUnit == B) { |
| codeUnit = BACKSPACE; |
| } else if (codeUnit == F) { |
| codeUnit = FORMFEED; |
| } else if (codeUnit == N) { |
| codeUnit = LF; |
| } else if (codeUnit == R) { |
| codeUnit = CR; |
| } else if (codeUnit == T) { |
| codeUnit = TAB; |
| } else if (codeUnit == U) { |
| throw new UnsupportedError('unicode escapes'); |
| } else if (codeUnit == QUOTE || |
| codeUnit == SLASH || |
| codeUnit == BACKSLASH) { |
| // Ok. |
| } else { |
| _fail(); |
| } |
| } |
| charCodes.add(codeUnit); |
| position++; |
| } |
| if (codeUnit != QUOTE) { |
| _fail(); |
| } |
| position++; |
| return new String.fromCharCodes(charCodes); |
| } |
| |
| Map _decodeMap() { |
| int codeUnit = codeUnits[position]; |
| if (codeUnit != LEFT_BRACE) { |
| _fail(); |
| } |
| position++; |
| _trimWhitespace(); |
| Map result = {}; |
| while (position < length) { |
| codeUnit = codeUnits[position]; |
| if (codeUnit == RIGHT_BRACE) { |
| break; |
| } |
| String key = _decodeString(); |
| _trimWhitespace(); |
| if (position < length) { |
| codeUnit = codeUnits[position]; |
| if (codeUnit == COLON) { |
| position++; |
| _trimWhitespace(); |
| } else { |
| _fail(); |
| } |
| } else { |
| _fail(); |
| } |
| var value = _decodeValue(); |
| result[key] = value; |
| _trimWhitespace(); |
| if (position < length) { |
| codeUnit = codeUnits[position]; |
| if (codeUnit == COMMA) { |
| position++; |
| _trimWhitespace(); |
| continue; |
| } else { |
| break; |
| } |
| } |
| } |
| |
| if (codeUnit != RIGHT_BRACE) { |
| _fail(); |
| } |
| position++; |
| return result; |
| } |
| |
| List _decodeList() { |
| int codeUnit = codeUnits[position]; |
| if (codeUnit != LEFT_BRACKET) { |
| _fail(); |
| } |
| position++; |
| _trimWhitespace(); |
| List result = []; |
| while (position < length) { |
| codeUnit = codeUnits[position]; |
| if (codeUnit == RIGHT_BRACKET) { |
| break; |
| } |
| result.add(_decodeValue()); |
| _trimWhitespace(); |
| if (position < length) { |
| codeUnit = codeUnits[position]; |
| if (codeUnit == COMMA) { |
| position++; |
| _trimWhitespace(); |
| continue; |
| } else { |
| break; |
| } |
| } |
| } |
| |
| if (codeUnit != RIGHT_BRACKET) { |
| _fail(); |
| } |
| position++; |
| return result; |
| } |
| |
| bool _decodeTrue() { |
| match(TRUE); |
| return true; |
| } |
| |
| bool _decodeFalse() { |
| match(FALSE); |
| return false; |
| } |
| |
| Null _decodeNull() { |
| match(NULL); |
| return null; |
| } |
| |
| void match(List<int> codes) { |
| if (position + codes.length > length) { |
| _fail(); |
| } |
| for (int i = 0; i < codes.length; i++) { |
| if (codes[i] != codeUnits[position + i]) { |
| _fail(); |
| } |
| } |
| position += codes.length; |
| } |
| |
| num _decodeNumber() { |
| throw new UnsupportedError('_decodeNumber'); |
| } |
| |
| void _fail() { |
| throw new ArgumentError("Unexpected value: " |
| "'${new String.fromCharCodes(codeUnits, position)}'."); |
| } |
| } |