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Unified Diff: yaml/lib/src/scanner.dart

Issue 1400473008: Roll Observatory packages and add a roll script (Closed) Base URL: git@github.com:dart-lang/observatory_pub_packages.git@master
Patch Set: Created 5 years, 2 months ago
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Index: yaml/lib/src/scanner.dart
diff --git a/yaml/lib/src/scanner.dart b/yaml/lib/src/scanner.dart
deleted file mode 100644
index 2e02a8f7de8097b36fa0d261a4f0454b1ac37f1b..0000000000000000000000000000000000000000
--- a/yaml/lib/src/scanner.dart
+++ /dev/null
@@ -1,1683 +0,0 @@
-// Copyright (c) 2014, 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.
-
-library yaml.scanner;
-
-import 'package:collection/collection.dart';
-import 'package:string_scanner/string_scanner.dart';
-import 'package:source_span/source_span.dart';
-
-import 'style.dart';
-import 'token.dart';
-import 'utils.dart';
-import 'yaml_exception.dart';
-
-/// A scanner that reads a string of Unicode characters and emits [Token]s.
-///
-/// This is based on the libyaml scanner, available at
-/// https://github.com/yaml/libyaml/blob/master/src/scanner.c. The license for
-/// that is available in ../../libyaml-license.txt.
-class Scanner {
- static const TAB = 0x9;
- static const LF = 0xA;
- static const CR = 0xD;
- static const SP = 0x20;
- static const DOLLAR = 0x24;
- static const LEFT_PAREN = 0x28;
- static const RIGHT_PAREN = 0x29;
- static const PLUS = 0x2B;
- static const COMMA = 0x2C;
- static const HYPHEN = 0x2D;
- static const PERIOD = 0x2E;
- static const QUESTION = 0x3F;
- static const COLON = 0x3A;
- static const SEMICOLON = 0x3B;
- static const EQUALS = 0x3D;
- static const LEFT_SQUARE = 0x5B;
- static const RIGHT_SQUARE = 0x5D;
- static const LEFT_CURLY = 0x7B;
- static const RIGHT_CURLY = 0x7D;
- static const HASH = 0x23;
- static const AMPERSAND = 0x26;
- static const ASTERISK = 0x2A;
- static const EXCLAMATION = 0x21;
- static const VERTICAL_BAR = 0x7C;
- static const LEFT_ANGLE = 0x3C;
- static const RIGHT_ANGLE = 0x3E;
- static const SINGLE_QUOTE = 0x27;
- static const DOUBLE_QUOTE = 0x22;
- static const PERCENT = 0x25;
- static const AT = 0x40;
- static const GRAVE_ACCENT = 0x60;
- static const TILDE = 0x7E;
-
- static const NULL = 0x0;
- static const BELL = 0x7;
- static const BACKSPACE = 0x8;
- static const VERTICAL_TAB = 0xB;
- static const FORM_FEED = 0xC;
- static const ESCAPE = 0x1B;
- static const SLASH = 0x2F;
- static const BACKSLASH = 0x5C;
- static const UNDERSCORE = 0x5F;
- static const NEL = 0x85;
- static const NBSP = 0xA0;
- static const LINE_SEPARATOR = 0x2028;
- static const PARAGRAPH_SEPARATOR = 0x2029;
- static const BOM = 0xFEFF;
-
- static const NUMBER_0 = 0x30;
- static const NUMBER_9 = 0x39;
-
- static const LETTER_A = 0x61;
- static const LETTER_B = 0x62;
- static const LETTER_E = 0x65;
- static const LETTER_F = 0x66;
- static const LETTER_N = 0x6E;
- static const LETTER_R = 0x72;
- static const LETTER_T = 0x74;
- static const LETTER_U = 0x75;
- static const LETTER_V = 0x76;
- static const LETTER_X = 0x78;
- static const LETTER_Z = 0x7A;
-
- static const LETTER_CAP_A = 0x41;
- static const LETTER_CAP_F = 0x46;
- static const LETTER_CAP_L = 0x4C;
- static const LETTER_CAP_N = 0x4E;
- static const LETTER_CAP_P = 0x50;
- static const LETTER_CAP_U = 0x55;
- static const LETTER_CAP_X = 0x58;
- static const LETTER_CAP_Z = 0x5A;
-
- /// The underlying [SpanScanner] used to read characters from the source text.
- ///
- /// This is also used to track line and column information and to generate
- /// [SourceSpan]s.
- final SpanScanner _scanner;
-
- /// Whether this scanner has produced a [TokenType.STREAM_START] token
- /// indicating the beginning of the YAML stream.
- var _streamStartProduced = false;
-
- /// Whether this scanner has produced a [TokenType.STREAM_END] token
- /// indicating the end of the YAML stream.
- var _streamEndProduced = false;
-
- /// The queue of tokens yet to be emitted.
- ///
- /// These are queued up in advance so that [TokenType.KEY] tokens can be
- /// inserted once the scanner determines that a series of tokens represents a
- /// mapping key.
- final _tokens = new QueueList<Token>();
-
- /// The number of tokens that have been emitted.
- ///
- /// This doesn't count tokens in [tokens].
- var _tokensParsed = 0;
-
- /// Whether the next token in [_tokens] is ready to be returned.
- ///
- /// It might not be ready if there may still be a [TokenType.KEY] inserted
- /// before it.
- var _tokenAvailable = false;
-
- /// The stack of indent levels for the current nested block contexts.
- ///
- /// The YAML spec specifies that the initial indentation level is -1 spaces.
- final _indents = <int>[-1];
-
- /// Whether a simple key is allowed in this context.
- ///
- /// A simple key refers to any mapping key that doesn't have an explicit "?".
- var _simpleKeyAllowed = true;
-
- /// The stack of potential simple keys for each level of flow nesting.
- ///
- /// Entries in this list may be `null`, indicating that there is no valid
- /// simple key for the associated level of nesting.
- ///
- /// When a ":" is parsed and there's a simple key available, a [TokenType.KEY]
- /// token is inserted in [_tokens] before that key's token. This allows the
- /// parser to tell that the key is intended to be a mapping key.
- final _simpleKeys = <_SimpleKey>[null];
-
- /// The current indentation level.
- int get _indent => _indents.last;
-
- /// Whether the scanner's currently positioned in a block-level structure (as
- /// opposed to flow-level).
- bool get _inBlockContext => _simpleKeys.length == 1;
-
- /// Whether the current character is a line break or the end of the source.
- bool get _isBreakOrEnd => _scanner.isDone || _isBreak;
-
- /// Whether the current character is a line break.
- bool get _isBreak => _isBreakAt(0);
-
- /// Whether the current character is whitespace or the end of the source.
- bool get _isBlankOrEnd => _isBlankOrEndAt(0);
-
- /// Whether the current character is whitespace.
- bool get _isBlank => _isBlankAt(0);
-
- /// Whether the current character is a valid tag name character.
- ///
- /// See http://yaml.org/spec/1.2/spec.html#ns-tag-name.
- bool get _isTagChar {
- var char = _scanner.peekChar();
- if (char == null) return false;
- switch (char) {
- case HYPHEN:
- case SEMICOLON:
- case SLASH:
- case COLON:
- case AT:
- case AMPERSAND:
- case EQUALS:
- case PLUS:
- case DOLLAR:
- case PERIOD:
- case TILDE:
- case QUESTION:
- case ASTERISK:
- case SINGLE_QUOTE:
- case LEFT_PAREN:
- case RIGHT_PAREN:
- case PERCENT:
- return true;
- default:
- return (char >= NUMBER_0 && char <= NUMBER_9) ||
- (char >= LETTER_A && char <= LETTER_Z) ||
- (char >= LETTER_CAP_A && char <= LETTER_CAP_Z);
- }
- }
-
- /// Whether the current character is a valid anchor name character.
- ///
- /// See http://yaml.org/spec/1.2/spec.html#ns-anchor-name.
- bool get _isAnchorChar {
- if (!_isNonSpace) return false;
-
- switch (_scanner.peekChar()) {
- case COMMA:
- case LEFT_SQUARE:
- case RIGHT_SQUARE:
- case LEFT_CURLY:
- case RIGHT_CURLY:
- return false;
- default:
- return true;
- }
- }
-
- /// Whether the character at the current position is a decimal digit.
- bool get _isDigit {
- var char = _scanner.peekChar();
- return char != null && (char >= NUMBER_0 && char <= NUMBER_9);
- }
-
- /// Whether the character at the current position is a hexidecimal
- /// digit.
- bool get _isHex {
- var char = _scanner.peekChar();
- if (char == null) return false;
- return (char >= NUMBER_0 && char <= NUMBER_9) ||
- (char >= LETTER_A && char <= LETTER_F) ||
- (char >= LETTER_CAP_A && char <= LETTER_CAP_F);
- }
-
- /// Whether the character at the current position is a plain character.
- ///
- /// See http://yaml.org/spec/1.2/spec.html#ns-plain-char(c).
- bool get _isPlainChar => _isPlainCharAt(0);
-
- /// Whether the character at the current position is a printable character
- /// other than a line break or byte-order mark.
- ///
- /// See http://yaml.org/spec/1.2/spec.html#nb-char.
- bool get _isNonBreak {
- var char = _scanner.peekChar();
- if (char == null) return false;
- switch (char) {
- case LF:
- case CR:
- case BOM:
- return false;
- case TAB:
- case NEL:
- return true;
- default:
- return (char >= 0x00020 && char <= 0x00007E) ||
- (char >= 0x000A0 && char <= 0x00D7FF) ||
- (char >= 0x0E000 && char <= 0x00FFFD) ||
- (char >= 0x10000 && char <= 0x10FFFF);
- }
- }
-
- /// Whether the character at the current position is a printable character
- /// other than whitespace.
- ///
- /// See http://yaml.org/spec/1.2/spec.html#nb-char.
- bool get _isNonSpace {
- var char = _scanner.peekChar();
- if (char == null) return false;
- switch (char) {
- case LF:
- case CR:
- case BOM:
- case SP:
- return false;
- case NEL:
- return true;
- default:
- return (char >= 0x00020 && char <= 0x00007E) ||
- (char >= 0x000A0 && char <= 0x00D7FF) ||
- (char >= 0x0E000 && char <= 0x00FFFD) ||
- (char >= 0x10000 && char <= 0x10FFFF);
- }
- }
-
- /// Returns Whether or not the current character begins a documentation
- /// indicator.
- ///
- /// If so, this sets the scanner's last match to that indicator.
- bool get _isDocumentIndicator {
- return _scanner.column == 0 && _isBlankOrEndAt(3) &&
- (_scanner.matches('---') || _scanner.matches('...'));
- }
-
- /// Creates a scanner that scans [source].
- ///
- /// [sourceUrl] can be a String or a [Uri].
- Scanner(String source, {sourceUrl})
- : _scanner = new SpanScanner.eager(source, sourceUrl: sourceUrl);
-
- /// Consumes and returns the next token.
- Token scan() {
- if (_streamEndProduced) throw new StateError("Out of tokens.");
- if (!_tokenAvailable) _fetchMoreTokens();
-
- var token = _tokens.removeFirst();
- _tokenAvailable = false;
- _tokensParsed++;
- _streamEndProduced = token is Token &&
- token.type == TokenType.STREAM_END;
- return token;
- }
-
- /// Consumes the next token and returns the one after that.
- Token advance() {
- scan();
- return peek();
- }
-
- /// Returns the next token without consuming it.
- Token peek() {
- if (_streamEndProduced) return null;
- if (!_tokenAvailable) _fetchMoreTokens();
- return _tokens.first;
- }
-
- /// Ensures that [_tokens] contains at least one token which can be returned.
- void _fetchMoreTokens() {
- while (true) {
- if (_tokens.isNotEmpty) {
- _staleSimpleKeys();
-
- // If the current token could be a simple key, we need to scan more
- // tokens until we determine whether it is or not. Otherwise we might
- // not emit the `KEY` token before we emit the value of the key.
- if (!_simpleKeys.any((key) =>
- key != null && key.tokenNumber == _tokensParsed)) {
- break;
- }
- }
-
- _fetchNextToken();
- }
- _tokenAvailable = true;
- }
-
- /// The dispatcher for token fetchers.
- void _fetchNextToken() {
- if (!_streamStartProduced) {
- _fetchStreamStart();
- return;
- }
-
- _scanToNextToken();
- _staleSimpleKeys();
- _unrollIndent(_scanner.column);
-
- if (_scanner.isDone) {
- _fetchStreamEnd();
- return;
- }
-
- if (_scanner.column == 0) {
- if (_scanner.peekChar() == PERCENT) {
- _fetchDirective();
- return;
- }
-
- if (_isBlankOrEndAt(3)) {
- if (_scanner.matches('---')) {
- _fetchDocumentIndicator(TokenType.DOCUMENT_START);
- return;
- }
-
- if (_scanner.matches('...')) {
- _fetchDocumentIndicator(TokenType.DOCUMENT_END);
- return;
- }
- }
- }
-
- switch (_scanner.peekChar()) {
- case LEFT_SQUARE:
- _fetchFlowCollectionStart(TokenType.FLOW_SEQUENCE_START);
- return;
- case LEFT_CURLY:
- _fetchFlowCollectionStart(TokenType.FLOW_MAPPING_START);
- return;
- case RIGHT_SQUARE:
- _fetchFlowCollectionEnd(TokenType.FLOW_SEQUENCE_END);
- return;
- case RIGHT_CURLY:
- _fetchFlowCollectionEnd(TokenType.FLOW_MAPPING_END);
- return;
- case COMMA:
- _fetchFlowEntry();
- return;
- case ASTERISK:
- _fetchAnchor(anchor: false);
- return;
- case AMPERSAND:
- _fetchAnchor(anchor: true);
- return;
- case EXCLAMATION:
- _fetchTag();
- return;
- case SINGLE_QUOTE:
- _fetchFlowScalar(singleQuote: true);
- return;
- case DOUBLE_QUOTE:
- _fetchFlowScalar(singleQuote: false);
- return;
- case VERTICAL_BAR:
- if (!_inBlockContext) _invalidScalarCharacter();
- _fetchBlockScalar(literal: true);
- return;
- case RIGHT_ANGLE:
- if (!_inBlockContext) _invalidScalarCharacter();
- _fetchBlockScalar(literal: false);
- return;
- case PERCENT:
- case AT:
- case GRAVE_ACCENT:
- _invalidScalarCharacter();
- return;
-
- // These characters may sometimes begin plain scalars.
- case HYPHEN:
- if (_isPlainCharAt(1)) {
- _fetchPlainScalar();
- } else {
- _fetchBlockEntry();
- }
- return;
- case QUESTION:
- if (_isPlainCharAt(1)) {
- _fetchPlainScalar();
- } else {
- _fetchKey();
- }
- return;
- case COLON:
- if (!_inBlockContext && _tokens.isNotEmpty) {
- // If a colon follows a "JSON-like" value (an explicit map or list, or
- // a quoted string) it isn't required to have whitespace after it
- // since it unambiguously describes a map.
- var token = _tokens.last;
- if (token.type == TokenType.FLOW_SEQUENCE_END ||
- token.type == TokenType.FLOW_MAPPING_END ||
- (token.type == TokenType.SCALAR && token.style.isQuoted)) {
- _fetchValue();
- return;
- }
- }
-
- if (_isPlainCharAt(1)) {
- _fetchPlainScalar();
- } else {
- _fetchValue();
- }
- return;
- default:
- if (!_isNonBreak) _invalidScalarCharacter();
-
- _fetchPlainScalar();
- return;
- }
-
- throw 'Inaccessible';
- }
-
- /// Throws an error about a disallowed character.
- void _invalidScalarCharacter() =>
- _scanner.error("Unexpected character.", length: 1);
-
- /// Checks the list of potential simple keys and remove the positions that
- /// cannot contain simple keys anymore.
- void _staleSimpleKeys() {
- for (var i = 0; i < _simpleKeys.length; i++) {
- var key = _simpleKeys[i];
- if (key == null) continue;
-
- // libyaml requires that all simple keys be a single line and no longer
- // than 1024 characters. However, in section 7.4.2 of the spec
- // (http://yaml.org/spec/1.2/spec.html#id2790832), these restrictions are
- // only applied when the curly braces are omitted. It's difficult to
- // retain enough context to know which keys need to have the restriction
- // placed on them, so for now we go the other direction and allow
- // everything but multiline simple keys in a block context.
- if (!_inBlockContext) continue;
-
- if (key.line == _scanner.line) continue;
-
- if (key.required) {
- throw new YamlException("Expected ':'.", _scanner.emptySpan);
- }
-
- _simpleKeys[i] = null;
- }
- }
-
- /// Checks if a simple key may start at the current position and saves it if
- /// so.
- void _saveSimpleKey() {
- // A simple key is required at the current position if the scanner is in the
- // block context and the current column coincides with the indentation
- // level.
- var required = _inBlockContext && _indent == _scanner.column;
-
- // A simple key is required only when it is the first token in the current
- // line. Therefore it is always allowed. But we add a check anyway.
- assert(_simpleKeyAllowed || !required);
-
- if (!_simpleKeyAllowed) return;
-
- // If the current position may start a simple key, save it.
- _removeSimpleKey();
- _simpleKeys[_simpleKeys.length - 1] = new _SimpleKey(
- _tokensParsed + _tokens.length,
- _scanner.line,
- _scanner.column,
- _scanner.location,
- required: required);
- }
-
- /// Removes a potential simple key at the current flow level.
- void _removeSimpleKey() {
- var key = _simpleKeys.last;
- if (key != null && key.required) {
- throw new YamlException("Could not find expected ':' for simple key.",
- key.location.pointSpan());
- }
-
- _simpleKeys[_simpleKeys.length - 1] = null;
- }
-
- /// Increases the flow level and resizes the simple key list.
- void _increaseFlowLevel() {
- _simpleKeys.add(null);
- }
-
- /// Decreases the flow level.
- void _decreaseFlowLevel() {
- if (_inBlockContext) return;
- _simpleKeys.removeLast();
- }
-
- /// Pushes the current indentation level to the stack and sets the new level
- /// if [column] is greater than [_indent].
- ///
- /// If it is, appends or inserts the specified token into [_tokens]. If
- /// [tokenNumber] is provided, the corresponding token will be replaced;
- /// otherwise, the token will be added at the end.
- void _rollIndent(int column, TokenType type, SourceLocation location,
- {int tokenNumber}) {
- if (!_inBlockContext) return;
- if (_indent != -1 && _indent >= column) return;
-
- // Push the current indentation level to the stack and set the new
- // indentation level.
- _indents.add(column);
-
- // Create a token and insert it into the queue.
- var token = new Token(type, location.pointSpan());
- if (tokenNumber == null) {
- _tokens.add(token);
- } else {
- _tokens.insert(tokenNumber - _tokensParsed, token);
- }
- }
-
- /// Pops indentation levels from [_indents] until the current level becomes
- /// less than or equal to [column].
- ///
- /// For each indentation level, appends a [TokenType.BLOCK_END] token.
- void _unrollIndent(int column) {
- if (!_inBlockContext) return;
-
- while (_indent > column) {
- _tokens.add(new Token(TokenType.BLOCK_END, _scanner.emptySpan));
- _indents.removeLast();
- }
- }
-
- /// Pops indentation levels from [_indents] until the current level resets to
- /// -1.
- ///
- /// For each indentation level, appends a [TokenType.BLOCK_END] token.
- void _resetIndent() => _unrollIndent(-1);
-
- /// Produces a [TokenType.STREAM_START] token.
- void _fetchStreamStart() {
- // Much of libyaml's initialization logic here is done in variable
- // initializers instead.
- _streamStartProduced = true;
- _tokens.add(new Token(TokenType.STREAM_START, _scanner.emptySpan));
- }
-
- /// Produces a [TokenType.STREAM_END] token.
- void _fetchStreamEnd() {
- _resetIndent();
- _removeSimpleKey();
- _simpleKeyAllowed = false;
- _tokens.add(new Token(TokenType.STREAM_END, _scanner.emptySpan));
- }
-
- /// Produces a [TokenType.VERSION_DIRECTIVE] or [TokenType.TAG_DIRECTIVE]
- /// token.
- void _fetchDirective() {
- _resetIndent();
- _removeSimpleKey();
- _simpleKeyAllowed = false;
- var directive = _scanDirective();
- if (directive != null) _tokens.add(directive);
- }
-
- /// Produces a [TokenType.DOCUMENT_START] or [TokenType.DOCUMENT_END] token.
- void _fetchDocumentIndicator(TokenType type) {
- _resetIndent();
- _removeSimpleKey();
- _simpleKeyAllowed = false;
-
- // Consume the indicator token.
- var start = _scanner.state;
- _scanner.readChar();
- _scanner.readChar();
- _scanner.readChar();
-
- _tokens.add(new Token(type, _scanner.spanFrom(start)));
- }
-
- /// Produces a [TokenType.FLOW_SEQUENCE_START] or
- /// [TokenType.FLOW_MAPPING_START] token.
- void _fetchFlowCollectionStart(TokenType type) {
- _saveSimpleKey();
- _increaseFlowLevel();
- _simpleKeyAllowed = true;
- _addCharToken(type);
- }
-
- /// Produces a [TokenType.FLOW_SEQUENCE_END] or [TokenType.FLOW_MAPPING_END]
- /// token.
- void _fetchFlowCollectionEnd(TokenType type) {
- _removeSimpleKey();
- _decreaseFlowLevel();
- _simpleKeyAllowed = false;
- _addCharToken(type);
- }
-
- /// Produces a [TokenType.FLOW_ENTRY] token.
- void _fetchFlowEntry() {
- _removeSimpleKey();
- _simpleKeyAllowed = true;
- _addCharToken(TokenType.FLOW_ENTRY);
- }
-
- /// Produces a [TokenType.BLOCK_ENTRY] token.
- void _fetchBlockEntry() {
- if (_inBlockContext) {
- if (!_simpleKeyAllowed) {
- throw new YamlException(
- "Block sequence entries are not allowed here.",
- _scanner.emptySpan);
- }
-
- _rollIndent(
- _scanner.column,
- TokenType.BLOCK_SEQUENCE_START,
- _scanner.location);
- } else {
- // It is an error for the '-' indicator to occur in the flow context, but
- // we let the Parser detect and report it because it's able to point to
- // the context.
- }
-
- _removeSimpleKey();
- _simpleKeyAllowed = true;
- _addCharToken(TokenType.BLOCK_ENTRY);
- }
-
- /// Produces the [TokenType.KEY] token.
- void _fetchKey() {
- if (_inBlockContext) {
- if (!_simpleKeyAllowed) {
- throw new YamlException("Mapping keys are not allowed here.",
- _scanner.emptySpan);
- }
-
- _rollIndent(
- _scanner.column,
- TokenType.BLOCK_MAPPING_START,
- _scanner.location);
- }
-
- // Simple keys are allowed after `?` in a block context.
- _simpleKeyAllowed = _inBlockContext;
- _addCharToken(TokenType.KEY);
- }
-
- /// Produces the [TokenType.VALUE] token.
- void _fetchValue() {
- var simpleKey = _simpleKeys.last;
- if (simpleKey != null) {
- // Add a [TokenType.KEY] directive before the first token of the simple
- // key so the parser knows that it's part of a key/value pair.
- _tokens.insert(simpleKey.tokenNumber - _tokensParsed,
- new Token(TokenType.KEY, simpleKey.location.pointSpan()));
-
- // In the block context, we may need to add the
- // [TokenType.BLOCK_MAPPING_START] token.
- _rollIndent(
- simpleKey.column,
- TokenType.BLOCK_MAPPING_START,
- simpleKey.location,
- tokenNumber: simpleKey.tokenNumber);
-
- // Remove the simple key.
- _simpleKeys[_simpleKeys.length - 1] = null;
-
- // A simple key cannot follow another simple key.
- _simpleKeyAllowed = false;
- } else if (_inBlockContext) {
- if (!_simpleKeyAllowed) {
- throw new YamlException(
- "Mapping values are not allowed here. Did you miss a colon "
- "earlier?",
- _scanner.emptySpan);
- }
-
- // If we're here, we've found the ':' indicator following a complex key.
-
- _rollIndent(
- _scanner.column,
- TokenType.BLOCK_MAPPING_START,
- _scanner.location);
- _simpleKeyAllowed = true;
- } else if (_simpleKeyAllowed) {
- // If we're here, we've found the ':' indicator with an empty key. This
- // behavior differs from libyaml, which disallows empty implicit keys.
- _simpleKeyAllowed = false;
- _addCharToken(TokenType.KEY);
- }
-
- _addCharToken(TokenType.VALUE);
- }
-
- /// Adds a token with [type] to [_tokens].
- ///
- /// The span of the new token is the current character.
- void _addCharToken(TokenType type) {
- var start = _scanner.state;
- _scanner.readChar();
- _tokens.add(new Token(type, _scanner.spanFrom(start)));
- }
-
- /// Produces a [TokenType.ALIAS] or [TokenType.ANCHOR] token.
- void _fetchAnchor({bool anchor: true}) {
- _saveSimpleKey();
- _simpleKeyAllowed = false;
- _tokens.add(_scanAnchor(anchor: anchor));
- }
-
- /// Produces a [TokenType.TAG] token.
- void _fetchTag() {
- _saveSimpleKey();
- _simpleKeyAllowed = false;
- _tokens.add(_scanTag());
- }
-
- /// Produces a [TokenType.SCALAR] token with style [ScalarStyle.LITERAL] or
- /// [ScalarStyle.FOLDED].
- void _fetchBlockScalar({bool literal: false}) {
- _removeSimpleKey();
- _simpleKeyAllowed = true;
- _tokens.add(_scanBlockScalar(literal: literal));
- }
-
- /// Produces a [TokenType.SCALAR] token with style [ScalarStyle.SINGLE_QUOTED]
- /// or [ScalarStyle.DOUBLE_QUOTED].
- void _fetchFlowScalar({bool singleQuote: false}) {
- _saveSimpleKey();
- _simpleKeyAllowed = false;
- _tokens.add(_scanFlowScalar(singleQuote: singleQuote));
- }
-
- /// Produces a [TokenType.SCALAR] token with style [ScalarStyle.PLAIN].
- void _fetchPlainScalar() {
- _saveSimpleKey();
- _simpleKeyAllowed = false;
- _tokens.add(_scanPlainScalar());
- }
-
- /// Eats whitespace and comments until the next token is found.
- void _scanToNextToken() {
- var afterLineBreak = false;
- while (true) {
- // Allow the BOM to start a line.
- if (_scanner.column == 0) _scanner.scan("\uFEFF");
-
- // Eat whitespace.
- //
- // libyaml disallows tabs after "-", "?", or ":", but the spec allows
- // them. See section 6.2: http://yaml.org/spec/1.2/spec.html#id2778241.
- while (_scanner.peekChar() == SP ||
- ((!_inBlockContext || !afterLineBreak) &&
- _scanner.peekChar() == TAB)) {
- _scanner.readChar();
- }
-
- if (_scanner.peekChar() == TAB) {
- _scanner.error("Tab characters are not allowed as indentation.",
- length: 1);
- }
-
- // Eat a comment until a line break.
- _skipComment();
-
- // If we're at a line break, eat it.
- if (_isBreak) {
- _skipLine();
-
- // In the block context, a new line may start a simple key.
- if (_inBlockContext) _simpleKeyAllowed = true;
- afterLineBreak = true;
- } else {
- // Otherwise we've found a token.
- break;
- }
- }
- }
-
- /// Scans a [TokenType.YAML_DIRECTIVE] or [TokenType.TAG_DIRECTIVE] token.
- ///
- /// %YAML 1.2 # a comment \n
- /// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- /// %TAG !yaml! tag:yaml.org,2002: \n
- /// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- Token _scanDirective() {
- var start = _scanner.state;
-
- // Eat '%'.
- _scanner.readChar();
-
- var token;
- var name = _scanDirectiveName();
- if (name == "YAML") {
- token = _scanVersionDirectiveValue(start);
- } else if (name == "TAG") {
- token = _scanTagDirectiveValue(start);
- } else {
- warn("Warning: unknown directive.", _scanner.spanFrom(start));
-
- // libyaml doesn't support unknown directives, but the spec says to ignore
- // them and warn: http://yaml.org/spec/1.2/spec.html#id2781147.
- while (!_isBreakOrEnd) {
- _scanner.readChar();
- }
-
- return null;
- }
-
- // Eat the rest of the line, including any comments.
- _skipBlanks();
- _skipComment();
-
- if (!_isBreakOrEnd) {
- throw new YamlException(
- "Expected comment or line break after directive.",
- _scanner.spanFrom(start));
- }
-
- _skipLine();
- return token;
- }
-
- /// Scans a directive name.
- ///
- /// %YAML 1.2 # a comment \n
- /// ^^^^
- /// %TAG !yaml! tag:yaml.org,2002: \n
- /// ^^^
- String _scanDirectiveName() {
- // libyaml only allows word characters in directive names, but the spec
- // disagrees: http://yaml.org/spec/1.2/spec.html#ns-directive-name.
- var start = _scanner.position;
- while (_isNonSpace) {
- _scanner.readChar();
- }
-
- var name = _scanner.substring(start);
- if (name.isEmpty) {
- throw new YamlException("Expected directive name.", _scanner.emptySpan);
- } else if (!_isBlankOrEnd) {
- throw new YamlException(
- "Unexpected character in directive name.", _scanner.emptySpan);
- }
-
- return name;
- }
-
- /// Scans the value of a version directive.
- ///
- /// %YAML 1.2 # a comment \n
- /// ^^^^^^
- Token _scanVersionDirectiveValue(LineScannerState start) {
- _skipBlanks();
-
- var major = _scanVersionDirectiveNumber();
- _scanner.expect('.');
- var minor = _scanVersionDirectiveNumber();
-
- return new VersionDirectiveToken(_scanner.spanFrom(start), major, minor);
- }
-
- /// Scans the version number of a version directive.
- ///
- /// %YAML 1.2 # a comment \n
- /// ^
- /// %YAML 1.2 # a comment \n
- /// ^
- int _scanVersionDirectiveNumber() {
- var start = _scanner.position;
- while (_isDigit) {
- _scanner.readChar();
- }
-
- var number = _scanner.substring(start);
- if (number.isEmpty) {
- throw new YamlException("Expected version number.", _scanner.emptySpan);
- }
-
- return int.parse(number);
- }
-
- /// Scans the value of a tag directive.
- ///
- /// %TAG !yaml! tag:yaml.org,2002: \n
- /// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
- Token _scanTagDirectiveValue(LineScannerState start) {
- _skipBlanks();
-
- var handle = _scanTagHandle(directive: true);
- if (!_isBlank) {
- throw new YamlException("Expected whitespace.", _scanner.emptySpan);
- }
-
- _skipBlanks();
-
- var prefix = _scanTagUri();
- if (!_isBlankOrEnd) {
- throw new YamlException("Expected whitespace.", _scanner.emptySpan);
- }
-
- return new TagDirectiveToken(_scanner.spanFrom(start), handle, prefix);
- }
-
- /// Scans a [TokenType.ANCHOR] token.
- Token _scanAnchor({bool anchor: true}) {
- var start = _scanner.state;
-
- // Eat the indicator character.
- _scanner.readChar();
-
- // libyaml only allows word characters in anchor names, but the spec
- // disagrees: http://yaml.org/spec/1.2/spec.html#ns-anchor-char.
- var startPosition = _scanner.position;
- while (_isAnchorChar) {
- _scanner.readChar();
- }
- var name = _scanner.substring(startPosition);
-
- var next = _scanner.peekChar();
- if (name.isEmpty ||
- (!_isBlankOrEnd && next != QUESTION && next != COLON &&
- next != COMMA && next != RIGHT_SQUARE && next != RIGHT_CURLY &&
- next != PERCENT && next != AT && next != GRAVE_ACCENT)) {
- throw new YamlException("Expected alphanumeric character.",
- _scanner.emptySpan);
- }
-
- if (anchor) {
- return new AnchorToken(_scanner.spanFrom(start), name);
- } else {
- return new AliasToken(_scanner.spanFrom(start), name);
- }
- }
-
- /// Scans a [TokenType.TAG] token.
- Token _scanTag() {
- var handle;
- var suffix;
- var start = _scanner.state;
-
- // Check if the tag is in the canonical form.
- if (_scanner.peekChar(1) == LEFT_ANGLE) {
- // Eat '!<'.
- _scanner.readChar();
- _scanner.readChar();
-
- handle = '';
- suffix = _scanTagUri();
-
- _scanner.expect('>');
- } else {
- // The tag has either the '!suffix' or the '!handle!suffix' form.
-
- // First, try to scan a handle.
- handle = _scanTagHandle();
-
- if (handle.length > 1 && handle.startsWith('!') && handle.endsWith('!')) {
- suffix = _scanTagUri(flowSeparators: false);
- } else {
- suffix = _scanTagUri(head: handle, flowSeparators: false);
-
- // There was no explicit handle.
- if (suffix.isEmpty) {
- // This is the special '!' tag.
- handle = null;
- suffix = '!';
- } else {
- handle = '!';
- }
- }
- }
-
- // libyaml insists on whitespace after a tag, but example 7.2 indicates
- // that it's not required: http://yaml.org/spec/1.2/spec.html#id2786720.
-
- return new TagToken(_scanner.spanFrom(start), handle, suffix);
- }
-
- /// Scans a tag handle.
- String _scanTagHandle({bool directive: false}) {
- _scanner.expect('!');
-
- var buffer = new StringBuffer('!');
-
- // libyaml only allows word characters in tags, but the spec disagrees:
- // http://yaml.org/spec/1.2/spec.html#ns-tag-char.
- var start = _scanner.position;
- while (_isTagChar) {
- _scanner.readChar();
- }
- buffer.write(_scanner.substring(start));
-
- if (_scanner.peekChar() == EXCLAMATION) {
- buffer.writeCharCode(_scanner.readChar());
- } else {
- // It's either the '!' tag or not really a tag handle. If it's a %TAG
- // directive, it's an error. If it's a tag token, it must be part of a
- // URI.
- if (directive && buffer.toString() != '!') _scanner.expect('!');
- }
-
- return buffer.toString();
- }
-
- /// Scans a tag URI.
- ///
- /// [head] is the initial portion of the tag that's already been scanned.
- /// [flowSeparators] indicates whether the tag URI can contain flow
- /// separators.
- String _scanTagUri({String head, bool flowSeparators: true}) {
- var length = head == null ? 0 : head.length;
- var buffer = new StringBuffer();
-
- // Copy the head if needed.
- //
- // Note that we don't copy the leading '!' character.
- if (length > 1) buffer.write(head.substring(1));
-
- // The set of characters that may appear in URI is as follows:
- //
- // '0'-'9', 'A'-'Z', 'a'-'z', '_', '-', ';', '/', '?', ':', '@', '&',
- // '=', '+', '$', ',', '.', '!', '~', '*', '\'', '(', ')', '[', ']',
- // '%'.
- //
- // In a shorthand tag annotation, the flow separators ',', '[', and ']' are
- // disallowed.
- var start = _scanner.position;
- var char = _scanner.peekChar();
- while (_isTagChar || (flowSeparators &&
- (char == COMMA || char == LEFT_SQUARE || char == RIGHT_SQUARE))) {
- _scanner.readChar();
- char = _scanner.peekChar();
- }
-
- // libyaml manually decodes the URL, but we don't have to do that.
- return Uri.decodeFull(_scanner.substring(start));
- }
-
- /// Scans a block scalar.
- Token _scanBlockScalar({bool literal: false}) {
- var start = _scanner.state;
-
- // Eat the indicator '|' or '>'.
- _scanner.readChar();
-
- // Check for a chomping indicator.
- var chomping = _Chomping.CLIP;
- var increment = 0;
- var char = _scanner.peekChar();
- if (char == PLUS || char == HYPHEN) {
- chomping = char == PLUS ? _Chomping.KEEP : _Chomping.STRIP;
- _scanner.readChar();
-
- // Check for an indentation indicator.
- if (_isDigit) {
- // Check that the indentation is greater than 0.
- if (_scanner.peekChar() == NUMBER_0) {
- throw new YamlException(
- "0 may not be used as an indentation indicator.",
- _scanner.spanFrom(start));
- }
-
- increment = _scanner.readChar() - NUMBER_0;
- }
- } else if (_isDigit) {
- // Do the same as above, but in the opposite order.
- if (_scanner.peekChar() == NUMBER_0) {
- throw new YamlException(
- "0 may not be used as an indentation indicator.",
- _scanner.spanFrom(start));
- }
-
- increment = _scanner.readChar() - NUMBER_0;
-
- char = _scanner.peekChar();
- if (char == PLUS || char == HYPHEN) {
- chomping = char == PLUS ? _Chomping.KEEP : _Chomping.STRIP;
- _scanner.readChar();
- }
- }
-
- // Eat whitespace and comments to the end of the line.
- _skipBlanks();
- _skipComment();
-
- // Check if we're at the end of the line.
- if (!_isBreakOrEnd) {
- throw new YamlException("Expected comment or line break.",
- _scanner.emptySpan);
- }
-
- _skipLine();
-
- // If the block scalar has an explicit indentation indicator, add that to
- // the current indentation to get the indentation level for the scalar's
- // contents.
- var indent = 0;
- if (increment != 0) {
- indent = _indent >= 0 ? _indent + increment : increment;
- }
-
- // Scan the leading line breaks to determine the indentation level if
- // needed.
- var pair = _scanBlockScalarBreaks(indent);
- indent = pair.first;
- var trailingBreaks = pair.last;
-
- // Scan the block scalar contents.
- var buffer = new StringBuffer();
- var leadingBreak = '';
- var leadingBlank = false;
- var trailingBlank = false;
- var end = _scanner.state;
- while (_scanner.column == indent && !_scanner.isDone) {
- // Check for a document indicator. libyaml doesn't do this, but the spec
- // mandates it. See example 9.5:
- // http://yaml.org/spec/1.2/spec.html#id2801606.
- if (_isDocumentIndicator) break;
-
- // We are at the beginning of a non-empty line.
-
- // Is there trailing whitespace?
- trailingBlank = _isBlank;
-
- // Check if we need to fold the leading line break.
- if (!literal && leadingBreak.isNotEmpty && !leadingBlank &&
- !trailingBlank) {
- // Do we need to join the lines with a space?
- if (trailingBreaks.isEmpty) buffer.writeCharCode(SP);
- } else {
- buffer.write(leadingBreak);
- }
- leadingBreak = '';
-
- // Append the remaining line breaks.
- buffer.write(trailingBreaks);
-
- // Is there leading whitespace?
- leadingBlank = _isBlank;
-
- var startPosition = _scanner.position;
- while (!_isBreakOrEnd) {
- _scanner.readChar();
- }
- buffer.write(_scanner.substring(startPosition));
- end = _scanner.state;
-
- // libyaml always reads a line here, but this breaks on block scalars at
- // the end of the document that end without newlines. See example 8.1:
- // http://yaml.org/spec/1.2/spec.html#id2793888.
- if (!_scanner.isDone) leadingBreak = _readLine();
-
- // Eat the following indentation and spaces.
- var pair = _scanBlockScalarBreaks(indent);
- indent = pair.first;
- trailingBreaks = pair.last;
- }
-
- // Chomp the tail.
- if (chomping != _Chomping.STRIP) buffer.write(leadingBreak);
- if (chomping == _Chomping.KEEP) buffer.write(trailingBreaks);
-
- return new ScalarToken(_scanner.spanFrom(start, end), buffer.toString(),
- literal ? ScalarStyle.LITERAL : ScalarStyle.FOLDED);
- }
-
- /// Scans indentation spaces and line breaks for a block scalar.
- ///
- /// Determines the intendation level if needed. Returns the new indentation
- /// level and the text of the line breaks.
- Pair<int, String> _scanBlockScalarBreaks(int indent) {
- var maxIndent = 0;
- var breaks = new StringBuffer();
-
- while (true) {
- while ((indent == 0 || _scanner.column < indent) &&
- _scanner.peekChar() == SP) {
- _scanner.readChar();
- }
-
- if (_scanner.column > maxIndent) maxIndent = _scanner.column;
-
- // libyaml throws an error here if a tab character is detected, but the
- // spec treats tabs like any other non-space character. See example 8.2:
- // http://yaml.org/spec/1.2/spec.html#id2794311.
-
- if (!_isBreak) break;
- breaks.write(_readLine());
- }
-
- if (indent == 0) {
- indent = maxIndent;
- if (indent < _indent + 1) indent = _indent + 1;
-
- // libyaml forces indent to be at least 1 here, but that doesn't seem to
- // be supported by the spec.
- }
-
- return new Pair(indent, breaks.toString());
- }
-
- // Scans a quoted scalar.
- Token _scanFlowScalar({bool singleQuote: false}) {
- var start = _scanner.state;
- var buffer = new StringBuffer();
-
- // Eat the left quote.
- _scanner.readChar();
-
- while (true) {
- // Check that there are no document indicators at the beginning of the
- // line.
- if (_isDocumentIndicator) {
- _scanner.error("Unexpected document indicator.");
- }
-
- if (_scanner.isDone) {
- throw new YamlException("Unexpected end of file.", _scanner.emptySpan);
- }
-
- var leadingBlanks = false;
- while (!_isBlankOrEnd) {
- var char = _scanner.peekChar();
- if (singleQuote && char == SINGLE_QUOTE &&
- _scanner.peekChar(1) == SINGLE_QUOTE) {
- // An escaped single quote.
- _scanner.readChar();
- _scanner.readChar();
- buffer.writeCharCode(SINGLE_QUOTE);
- } else if (char == (singleQuote ? SINGLE_QUOTE : DOUBLE_QUOTE)) {
- // The closing quote.
- break;
- } else if (!singleQuote && char == BACKSLASH && _isBreakAt(1)) {
- // An escaped newline.
- _scanner.readChar();
- _skipLine();
- leadingBlanks = true;
- break;
- } else if (!singleQuote && char == BACKSLASH) {
- var escapeStart = _scanner.state;
-
- // An escape sequence.
- var codeLength = null;
- switch (_scanner.peekChar(1)) {
- case NUMBER_0:
- buffer.writeCharCode(NULL);
- break;
- case LETTER_A:
- buffer.writeCharCode(BELL);
- break;
- case LETTER_B:
- buffer.writeCharCode(BACKSPACE);
- break;
- case LETTER_T:
- case TAB:
- buffer.writeCharCode(TAB);
- break;
- case LETTER_N:
- buffer.writeCharCode(LF);
- break;
- case LETTER_V:
- buffer.writeCharCode(VERTICAL_TAB);
- break;
- case LETTER_F:
- buffer.writeCharCode(FORM_FEED);
- break;
- case LETTER_R:
- buffer.writeCharCode(CR);
- break;
- case LETTER_E:
- buffer.writeCharCode(ESCAPE);
- break;
- case SP:
- case DOUBLE_QUOTE:
- case SLASH:
- case BACKSLASH:
- // libyaml doesn't support an escaped forward slash, but it was
- // added in YAML 1.2. See section 5.7:
- // http://yaml.org/spec/1.2/spec.html#id2776092
- buffer.writeCharCode(_scanner.peekChar(1));
- break;
- case LETTER_CAP_N:
- buffer.writeCharCode(NEL);
- break;
- case UNDERSCORE:
- buffer.writeCharCode(NBSP);
- break;
- case LETTER_CAP_L:
- buffer.writeCharCode(LINE_SEPARATOR);
- break;
- case LETTER_CAP_P:
- buffer.writeCharCode(PARAGRAPH_SEPARATOR);
- break;
- case LETTER_X:
- codeLength = 2;
- break;
- case LETTER_U:
- codeLength = 4;
- break;
- case LETTER_CAP_U:
- codeLength = 8;
- break;
- default:
- throw new YamlException("Unknown escape character.",
- _scanner.spanFrom(escapeStart));
- }
-
- _scanner.readChar();
- _scanner.readChar();
-
- if (codeLength != null) {
- var value = 0;
- for (var i = 0; i < codeLength; i++) {
- if (!_isHex) {
- _scanner.readChar();
- throw new YamlException(
- "Expected $codeLength-digit hexidecimal number.",
- _scanner.spanFrom(escapeStart));
- }
-
- value = (value << 4) + _asHex(_scanner.readChar());
- }
-
- // Check the value and write the character.
- if ((value >= 0xD800 && value <= 0xDFFF) || value > 0x10FFFF) {
- throw new YamlException(
- "Invalid Unicode character escape code.",
- _scanner.spanFrom(escapeStart));
- }
-
- buffer.writeCharCode(value);
- }
- } else {
- buffer.writeCharCode(_scanner.readChar());
- }
- }
-
- // Check if we're at the end of a scalar.
- if (_scanner.peekChar() == (singleQuote ? SINGLE_QUOTE : DOUBLE_QUOTE)) {
- break;
- }
-
- var whitespace = new StringBuffer();
- var leadingBreak = '';
- var trailingBreaks = new StringBuffer();
- while (_isBlank || _isBreak) {
- if (_isBlank) {
- // Consume a space or a tab.
- if (!leadingBlanks) {
- whitespace.writeCharCode(_scanner.readChar());
- } else {
- _scanner.readChar();
- }
- } else {
- // Check if it's a first line break.
- if (!leadingBlanks) {
- whitespace.clear();
- leadingBreak = _readLine();
- leadingBlanks = true;
- } else {
- trailingBreaks.write(_readLine());
- }
- }
- }
-
- // Join the whitespace or fold line breaks.
- if (leadingBlanks) {
- if (leadingBreak.isNotEmpty && trailingBreaks.isEmpty) {
- buffer.writeCharCode(SP);
- } else {
- buffer.write(trailingBreaks);
- }
- } else {
- buffer.write(whitespace);
- whitespace.clear();
- }
- }
-
- // Eat the right quote.
- _scanner.readChar();
-
- return new ScalarToken(_scanner.spanFrom(start), buffer.toString(),
- singleQuote ? ScalarStyle.SINGLE_QUOTED : ScalarStyle.DOUBLE_QUOTED);
- }
-
- /// Scans a plain scalar.
- Token _scanPlainScalar() {
- var start = _scanner.state;
- var end = _scanner.state;
- var buffer = new StringBuffer();
- var leadingBreak = '';
- var trailingBreaks = '';
- var whitespace = new StringBuffer();
- var indent = _indent + 1;
-
- while (true) {
- // Check for a document indicator.
- if (_isDocumentIndicator) break;
-
- // Check for a comment.
- if (_scanner.peekChar() == HASH) break;
-
- if (_isPlainChar) {
- // Join the whitespace or fold line breaks.
- if (leadingBreak.isNotEmpty) {
- if (trailingBreaks.isEmpty) {
- buffer.writeCharCode(SP);
- } else {
- buffer.write(trailingBreaks);
- }
- leadingBreak = '';
- trailingBreaks = '';
- } else {
- buffer.write(whitespace);
- whitespace.clear();
- }
- }
-
- // libyaml's notion of valid identifiers differs substantially from YAML
- // 1.2's. We use [_isPlainChar] instead of libyaml's character here.
- var startPosition = _scanner.position;
- while (_isPlainChar) {
- _scanner.readChar();
- }
- buffer.write(_scanner.substring(startPosition));
- end = _scanner.state;
-
- // Is it the end?
- if (!_isBlank && !_isBreak) break;
-
- while (_isBlank || _isBreak) {
- if (_isBlank) {
- // Check for a tab character messing up the intendation.
- if (leadingBreak.isNotEmpty && _scanner.column < indent &&
- _scanner.peekChar() == TAB) {
- _scanner.error("Expected a space but found a tab.", length: 1);
- }
-
- if (leadingBreak.isEmpty) {
- whitespace.writeCharCode(_scanner.readChar());
- } else {
- _scanner.readChar();
- }
- } else {
- // Check if it's a first line break.
- if (leadingBreak.isEmpty) {
- leadingBreak = _readLine();
- whitespace.clear();
- } else {
- trailingBreaks = _readLine();
- }
- }
- }
-
- // Check the indentation level.
- if (_inBlockContext && _scanner.column < indent) break;
- }
-
- // Allow a simple key after a plain scalar with leading blanks.
- if (leadingBreak.isNotEmpty) _simpleKeyAllowed = true;
-
- return new ScalarToken(_scanner.spanFrom(start, end), buffer.toString(),
- ScalarStyle.PLAIN);
- }
-
- /// Moves past the current line break, if there is one.
- void _skipLine() {
- var char = _scanner.peekChar();
- if (char != CR && char != LF) return;
- _scanner.readChar();
- if (char == CR && _scanner.peekChar() == LF) _scanner.readChar();
- }
-
- // Moves past the current line break and returns a newline.
- String _readLine() {
- var char = _scanner.peekChar();
-
- // libyaml supports NEL, PS, and LS characters as line separators, but this
- // is explicitly forbidden in section 5.4 of the YAML spec.
- if (char != CR && char != LF) {
- throw new YamlException("Expected newline.", _scanner.emptySpan);
- }
-
- _scanner.readChar();
- // CR LF | CR | LF -> LF
- if (char == CR && _scanner.peekChar() == LF) _scanner.readChar();
- return "\n";
- }
-
- // Returns whether the character at [offset] is whitespace.
- bool _isBlankAt(int offset) {
- var char = _scanner.peekChar(offset);
- return char == SP || char == TAB;
- }
-
- // Returns whether the character at [offset] is a line break.
- bool _isBreakAt(int offset) {
- // Libyaml considers NEL, LS, and PS to be line breaks as well, but that's
- // contrary to the spec.
- var char = _scanner.peekChar(offset);
- return char == CR || char == LF;
- }
-
- // Returns whether the character at [offset] is whitespace or past the end of
- // the source.
- bool _isBlankOrEndAt(int offset) {
- var char = _scanner.peekChar(offset);
- return char == null || char == SP || char == TAB || char == CR ||
- char == LF;
- }
-
- /// Returns whether the character at [offset] is a plain character.
- ///
- /// See http://yaml.org/spec/1.2/spec.html#ns-plain-char(c).
- bool _isPlainCharAt(int offset) {
- switch (_scanner.peekChar(offset)) {
- case COLON:
- return _isPlainSafeAt(offset + 1);
- case HASH:
- var previous = _scanner.peekChar(offset - 1);
- return previous != SP && previous != TAB;
- default:
- return _isPlainSafeAt(offset);
- }
- }
-
- /// Returns whether the character at [offset] is a plain-safe character.
- ///
- /// See http://yaml.org/spec/1.2/spec.html#ns-plain-safe(c).
- bool _isPlainSafeAt(int offset) {
- var char = _scanner.peekChar(offset);
- switch (char) {
- case COMMA:
- case LEFT_SQUARE:
- case RIGHT_SQUARE:
- case LEFT_CURLY:
- case RIGHT_CURLY:
- // These characters are delimiters in a flow context and thus are only
- // safe in a block context.
- return _inBlockContext;
- case SP:
- case TAB:
- case LF:
- case CR:
- case BOM:
- return false;
- case NEL:
- return true;
- default:
- return char != null &&
- ((char >= 0x00020 && char <= 0x00007E) ||
- (char >= 0x000A0 && char <= 0x00D7FF) ||
- (char >= 0x0E000 && char <= 0x00FFFD) ||
- (char >= 0x10000 && char <= 0x10FFFF));
- }
- }
-
- /// Returns the hexidecimal value of [char].
- int _asHex(int char) {
- if (char <= NUMBER_9) return char - NUMBER_0;
- if (char <= LETTER_CAP_F) return 10 + char - LETTER_CAP_A;
- return 10 + char - LETTER_A;
- }
-
- /// Moves the scanner past any blank characters.
- void _skipBlanks() {
- while (_isBlank) {
- _scanner.readChar();
- }
- }
-
- /// Moves the scanner past a comment, if one starts at the current position.
- void _skipComment() {
- if (_scanner.peekChar() != HASH) return;
- while (!_isBreakOrEnd) {
- _scanner.readChar();
- }
- }
-}
-
-/// A record of the location of a potential simple key.
-class _SimpleKey {
- /// The index of the token that begins the simple key.
- ///
- /// This is the index relative to all tokens emitted, rather than relative to
- /// [_tokens].
- final int tokenNumber;
-
- /// The source location of the beginning of the simple key.
- ///
- /// This is used for error reporting and for determining when a simple key is
- /// no longer on the current line.
- final SourceLocation location;
-
- /// The line on which the key appears.
- ///
- /// We could get this from [location], but that requires a binary search
- /// whereas this is O(1).
- final int line;
-
- /// The column on which the key appears.
- ///
- /// We could get this from [location], but that requires a binary search
- /// whereas this is O(1).
- final int column;
-
- /// Whether this key must exist for the document to be scanned.
- final bool required;
-
- _SimpleKey(this.tokenNumber, this.line, this.column, this.location,
- {bool required})
- : required = required;
-}
-
-/// An enum of chomping indicators that describe how to handle trailing
-/// whitespace for a block scalar.
-///
-/// See http://yaml.org/spec/1.2/spec.html#id2794534.
-class _Chomping {
- /// All trailing whitespace is discarded.
- static const STRIP = const _Chomping("STRIP");
-
- /// A single trailing newline is retained.
- static const CLIP = const _Chomping("CLIP");
-
- /// All trailing whitespace is preserved.
- static const KEEP = const _Chomping("KEEP");
-
- final String name;
-
- const _Chomping(this.name);
-
- String toString() => name;
-}
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