| // 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. |
| |
| import 'package:charcode/ascii.dart'; |
| import 'package:source_span/source_span.dart'; |
| |
| import 'equality.dart'; |
| import 'event.dart'; |
| import 'parser.dart'; |
| import 'yaml_document.dart'; |
| import 'yaml_exception.dart'; |
| import 'yaml_node.dart'; |
| |
| /// A loader that reads [Event]s emitted by a [Parser] and emits |
| /// [YamlDocument]s. |
| /// |
| /// This is based on the libyaml loader, available at |
| /// https://github.com/yaml/libyaml/blob/master/src/loader.c. The license for |
| /// that is available in ../../libyaml-license.txt. |
| class Loader { |
| /// The underlying [Parser] that generates [Event]s. |
| final Parser _parser; |
| |
| /// Aliases by the alias name. |
| final _aliases = new Map<String, YamlNode>(); |
| |
| /// The span of the entire stream emitted so far. |
| FileSpan get span => _span; |
| FileSpan _span; |
| |
| /// Creates a loader that loads [source]. |
| /// |
| /// [sourceUrl] can be a String or a [Uri]. |
| Loader(String source, {sourceUrl}) |
| : _parser = new Parser(source, sourceUrl: sourceUrl) { |
| var event = _parser.parse(); |
| _span = event.span; |
| assert(event.type == EventType.STREAM_START); |
| } |
| |
| /// Loads the next document from the stream. |
| /// |
| /// If there are no more documents, returns `null`. |
| YamlDocument load() { |
| if (_parser.isDone) return null; |
| |
| var event = _parser.parse(); |
| if (event.type == EventType.STREAM_END) { |
| _span = _span.expand(event.span); |
| return null; |
| } |
| |
| var document = _loadDocument(event); |
| _span = _span.expand(document.span); |
| _aliases.clear(); |
| return document; |
| } |
| |
| /// Composes a document object. |
| YamlDocument _loadDocument(DocumentStartEvent firstEvent) { |
| var contents = _loadNode(_parser.parse()); |
| |
| var lastEvent = _parser.parse() as DocumentEndEvent; |
| assert(lastEvent.type == EventType.DOCUMENT_END); |
| |
| return new YamlDocument.internal( |
| contents, |
| firstEvent.span.expand(lastEvent.span), |
| firstEvent.versionDirective, |
| firstEvent.tagDirectives, |
| startImplicit: firstEvent.isImplicit, |
| endImplicit: lastEvent.isImplicit); |
| } |
| |
| /// Composes a node. |
| YamlNode _loadNode(Event firstEvent) { |
| switch (firstEvent.type) { |
| case EventType.ALIAS: |
| return _loadAlias(firstEvent); |
| case EventType.SCALAR: |
| return _loadScalar(firstEvent); |
| case EventType.SEQUENCE_START: |
| return _loadSequence(firstEvent); |
| case EventType.MAPPING_START: |
| return _loadMapping(firstEvent); |
| default: |
| throw "Unreachable"; |
| } |
| } |
| |
| /// Registers an anchor. |
| void _registerAnchor(String anchor, YamlNode node) { |
| if (anchor == null) return; |
| |
| // libyaml throws an error for duplicate anchors, but example 7.1 makes it |
| // clear that they should be overridden: |
| // http://yaml.org/spec/1.2/spec.html#id2786448. |
| |
| _aliases[anchor] = node; |
| } |
| |
| /// Composes a node corresponding to an alias. |
| YamlNode _loadAlias(AliasEvent event) { |
| var alias = _aliases[event.name]; |
| if (alias != null) return alias; |
| |
| throw new YamlException("Undefined alias.", event.span); |
| } |
| |
| /// Composes a scalar node. |
| YamlNode _loadScalar(ScalarEvent scalar) { |
| var node; |
| if (scalar.tag == "!") { |
| node = new YamlScalar.internal(scalar.value, scalar); |
| } else if (scalar.tag != null) { |
| node = _parseByTag(scalar); |
| } else { |
| node = _parseScalar(scalar); |
| } |
| |
| _registerAnchor(scalar.anchor, node); |
| return node; |
| } |
| |
| /// Composes a sequence node. |
| YamlNode _loadSequence(SequenceStartEvent firstEvent) { |
| if (firstEvent.tag != "!" && |
| firstEvent.tag != null && |
| firstEvent.tag != "tag:yaml.org,2002:seq") { |
| throw new YamlException("Invalid tag for sequence.", firstEvent.span); |
| } |
| |
| var children = <YamlNode>[]; |
| var node = |
| new YamlList.internal(children, firstEvent.span, firstEvent.style); |
| _registerAnchor(firstEvent.anchor, node); |
| |
| var event = _parser.parse(); |
| while (event.type != EventType.SEQUENCE_END) { |
| children.add(_loadNode(event)); |
| event = _parser.parse(); |
| } |
| |
| setSpan(node, firstEvent.span.expand(event.span)); |
| return node; |
| } |
| |
| /// Composes a mapping node. |
| YamlNode _loadMapping(MappingStartEvent firstEvent) { |
| if (firstEvent.tag != "!" && |
| firstEvent.tag != null && |
| firstEvent.tag != "tag:yaml.org,2002:map") { |
| throw new YamlException("Invalid tag for mapping.", firstEvent.span); |
| } |
| |
| var children = deepEqualsMap<dynamic, YamlNode>(); |
| var node = |
| new YamlMap.internal(children, firstEvent.span, firstEvent.style); |
| _registerAnchor(firstEvent.anchor, node); |
| |
| var event = _parser.parse(); |
| while (event.type != EventType.MAPPING_END) { |
| var key = _loadNode(event); |
| var value = _loadNode(_parser.parse()); |
| if (children.containsKey(key)) { |
| throw new YamlException("Duplicate mapping key.", key.span); |
| } |
| |
| children[key] = value; |
| event = _parser.parse(); |
| } |
| |
| setSpan(node, firstEvent.span.expand(event.span)); |
| return node; |
| } |
| |
| /// Parses a scalar according to its tag name. |
| YamlScalar _parseByTag(ScalarEvent scalar) { |
| switch (scalar.tag) { |
| case "tag:yaml.org,2002:null": |
| var result = _parseNull(scalar); |
| if (result != null) return result; |
| throw new YamlException("Invalid null scalar.", scalar.span); |
| case "tag:yaml.org,2002:bool": |
| var result = _parseBool(scalar); |
| if (result != null) return result; |
| throw new YamlException("Invalid bool scalar.", scalar.span); |
| case "tag:yaml.org,2002:int": |
| var result = _parseNumber(scalar, allowFloat: false); |
| if (result != null) return result; |
| throw new YamlException("Invalid int scalar.", scalar.span); |
| case "tag:yaml.org,2002:float": |
| var result = _parseNumber(scalar, allowInt: false); |
| if (result != null) return result; |
| throw new YamlException("Invalid float scalar.", scalar.span); |
| case "tag:yaml.org,2002:str": |
| return new YamlScalar.internal(scalar.value, scalar); |
| default: |
| throw new YamlException('Undefined tag: ${scalar.tag}.', scalar.span); |
| } |
| } |
| |
| /// Parses [scalar], which may be one of several types. |
| YamlScalar _parseScalar(ScalarEvent scalar) => |
| _tryParseScalar(scalar) ?? new YamlScalar.internal(scalar.value, scalar); |
| |
| /// Tries to parse [scalar]. |
| /// |
| /// If parsing fails, this returns `null`, indicating that the scalar should |
| /// be parsed as a string. |
| YamlScalar _tryParseScalar(ScalarEvent scalar) { |
| // Quickly check for the empty string, which means null. |
| var length = scalar.value.length; |
| if (length == 0) return new YamlScalar.internal(null, scalar); |
| |
| // Dispatch on the first character. |
| var firstChar = scalar.value.codeUnitAt(0); |
| switch (firstChar) { |
| case $dot: |
| case $plus: |
| case $minus: |
| return _parseNumber(scalar); |
| case $n: |
| case $N: |
| return length == 4 ? _parseNull(scalar) : null; |
| case $t: |
| case $T: |
| return length == 4 ? _parseBool(scalar) : null; |
| case $f: |
| case $F: |
| return length == 5 ? _parseBool(scalar) : null; |
| case $tilde: |
| return length == 1 ? new YamlScalar.internal(null, scalar) : null; |
| default: |
| if (firstChar >= $0 && firstChar <= $9) return _parseNumber(scalar); |
| return null; |
| } |
| } |
| |
| /// Parse a null scalar. |
| /// |
| /// Returns a Dart `null` if parsing fails. |
| YamlScalar _parseNull(ScalarEvent scalar) { |
| switch (scalar.value) { |
| case "": |
| case "null": |
| case "Null": |
| case "NULL": |
| case "~": |
| return new YamlScalar.internal(null, scalar); |
| default: |
| return null; |
| } |
| } |
| |
| /// Parse a boolean scalar. |
| /// |
| /// Returns `null` if parsing fails. |
| YamlScalar _parseBool(ScalarEvent scalar) { |
| switch (scalar.value) { |
| case "true": |
| case "True": |
| case "TRUE": |
| return new YamlScalar.internal(true, scalar); |
| case "false": |
| case "False": |
| case "FALSE": |
| return new YamlScalar.internal(false, scalar); |
| default: |
| return null; |
| } |
| } |
| |
| /// Parses a numeric scalar. |
| /// |
| /// Returns `null` if parsing fails. |
| YamlNode _parseNumber(ScalarEvent scalar, |
| {bool allowInt: true, bool allowFloat: true}) { |
| var value = _parseNumberValue(scalar.value, |
| allowInt: allowInt, allowFloat: allowFloat); |
| return value == null ? null : new YamlScalar.internal(value, scalar); |
| } |
| |
| /// Parses the value of a number. |
| /// |
| /// Returns the number if it's parsed successfully, or `null` if it's not. |
| num _parseNumberValue(String contents, |
| {bool allowInt: true, bool allowFloat: true}) { |
| assert(allowInt || allowFloat); |
| |
| var firstChar = contents.codeUnitAt(0); |
| var length = contents.length; |
| |
| // Quick check for single digit integers. |
| if (allowInt && length == 1) { |
| var value = firstChar - $0; |
| return value >= 0 && value <= 9 ? value : null; |
| } |
| |
| var secondChar = contents.codeUnitAt(1); |
| |
| // Hexadecimal or octal integers. |
| if (allowInt && firstChar == $0) { |
| // int.parse supports 0x natively. |
| if (secondChar == $x) return int.parse(contents, onError: (_) => null); |
| |
| if (secondChar == $o) { |
| var afterRadix = contents.substring(2); |
| return int.parse(afterRadix, radix: 8, onError: (_) => null); |
| } |
| } |
| |
| // Int or float starting with a digit or a +/- sign. |
| if ((firstChar >= $0 && firstChar <= $9) || |
| ((firstChar == $plus || firstChar == $minus) && |
| secondChar >= $0 && |
| secondChar <= $9)) { |
| // Try to parse an int or, failing that, a double. |
| var result = null; |
| if (allowInt) { |
| // Pass "radix: 10" explicitly to ensure that "-0x10", which is valid |
| // Dart but invalid YAML, doesn't get parsed. |
| result = int.parse(contents, radix: 10, onError: (_) => null); |
| } |
| |
| if (allowFloat) result ??= double.parse(contents, (_) => null); |
| return result; |
| } |
| |
| if (!allowFloat) return null; |
| |
| // Now the only possibility is to parse a float starting with a dot or a |
| // sign and a dot, or the signed/unsigned infinity values and not-a-numbers. |
| if ((firstChar == $dot && secondChar >= $0 && secondChar <= $9) || |
| (firstChar == $minus || firstChar == $plus) && secondChar == $dot) { |
| // Starting with a . and a number or a sign followed by a dot. |
| if (length == 5) { |
| switch (contents) { |
| case "+.inf": |
| case "+.Inf": |
| case "+.INF": |
| return double.INFINITY; |
| case "-.inf": |
| case "-.Inf": |
| case "-.INF": |
| return -double.INFINITY; |
| } |
| } |
| |
| return double.parse(contents, (_) => null); |
| } |
| |
| if (length == 4 && firstChar == $dot) { |
| switch (contents) { |
| case ".inf": |
| case ".Inf": |
| case ".INF": |
| return double.INFINITY; |
| case ".nan": |
| case ".NaN": |
| case ".NAN": |
| return double.NAN; |
| } |
| } |
| |
| return null; |
| } |
| } |