Package org.yaml.snakeyaml.parser

Class ParserImpl

  • All Implemented Interfaces:
    Parser
    public class ParserImpl
extends java.lang.Object
implements Parser
     # The following YAML grammar is LL(1) and is parsed by a recursive descent
 parser.
 stream            ::= STREAM-START implicit_document? explicit_document* STREAM-END
 implicit_document ::= block_node DOCUMENT-END*
 explicit_document ::= DIRECTIVE* DOCUMENT-START block_node? DOCUMENT-END*
 block_node_or_indentless_sequence ::=
                       ALIAS
                       | properties (block_content | indentless_block_sequence)?
                       | block_content
                       | indentless_block_sequence
 block_node        ::= ALIAS
                       | properties block_content?
                       | block_content
 flow_node         ::= ALIAS
                       | properties flow_content?
                       | flow_content
 properties        ::= TAG ANCHOR? | ANCHOR TAG?
 block_content     ::= block_collection | flow_collection | SCALAR
 flow_content      ::= flow_collection | SCALAR
 block_collection  ::= block_sequence | block_mapping
 flow_collection   ::= flow_sequence | flow_mapping
 block_sequence    ::= BLOCK-SEQUENCE-START (BLOCK-ENTRY block_node?)* BLOCK-END
 indentless_sequence   ::= (BLOCK-ENTRY block_node?)+
 block_mapping     ::= BLOCK-MAPPING_START
                       ((KEY block_node_or_indentless_sequence?)?
                       (VALUE block_node_or_indentless_sequence?)?)*
                       BLOCK-END
 flow_sequence     ::= FLOW-SEQUENCE-START
                       (flow_sequence_entry FLOW-ENTRY)*
                       flow_sequence_entry?
                       FLOW-SEQUENCE-END
 flow_sequence_entry   ::= flow_node | KEY flow_node? (VALUE flow_node?)?
 flow_mapping      ::= FLOW-MAPPING-START
                       (flow_mapping_entry FLOW-ENTRY)*
                       flow_mapping_entry?
                       FLOW-MAPPING-END
 flow_mapping_entry    ::= flow_node | KEY flow_node? (VALUE flow_node?)?
 FIRST sets:
 stream: { STREAM-START }
 explicit_document: { DIRECTIVE DOCUMENT-START }
 implicit_document: FIRST(block_node)
 block_node: { ALIAS TAG ANCHOR SCALAR BLOCK-SEQUENCE-START BLOCK-MAPPING-START FLOW-SEQUENCE-START FLOW-MAPPING-START }
 flow_node: { ALIAS ANCHOR TAG SCALAR FLOW-SEQUENCE-START FLOW-MAPPING-START }
 block_content: { BLOCK-SEQUENCE-START BLOCK-MAPPING-START FLOW-SEQUENCE-START FLOW-MAPPING-START SCALAR }
 flow_content: { FLOW-SEQUENCE-START FLOW-MAPPING-START SCALAR }
 block_collection: { BLOCK-SEQUENCE-START BLOCK-MAPPING-START }
 flow_collection: { FLOW-SEQUENCE-START FLOW-MAPPING-START }
 block_sequence: { BLOCK-SEQUENCE-START }
 block_mapping: { BLOCK-MAPPING-START }
 block_node_or_indentless_sequence: { ALIAS ANCHOR TAG SCALAR BLOCK-SEQUENCE-START BLOCK-MAPPING-START FLOW-SEQUENCE-START FLOW-MAPPING-START BLOCK-ENTRY }
 indentless_sequence: { ENTRY }
 flow_collection: { FLOW-SEQUENCE-START FLOW-MAPPING-START }
 flow_sequence: { FLOW-SEQUENCE-START }
 flow_mapping: { FLOW-MAPPING-START }
 flow_sequence_entry: { ALIAS ANCHOR TAG SCALAR FLOW-SEQUENCE-START FLOW-MAPPING-START KEY }
 flow_mapping_entry: { ALIAS ANCHOR TAG SCALAR FLOW-SEQUENCE-START FLOW-MAPPING-START KEY }
    Since writing a recursive-descendant parser is a straightforward task, we do not give many comments here.

    • Constructor Detail

      • ParserImpl

        @Deprecated
public ParserImpl​(StreamReader reader)
        Deprecated.
        use options
        Create
        Parameters:
        reader - - input

      • ParserImpl

        @Deprecated
public ParserImpl​(StreamReader reader,
                  boolean parseComments)
        Deprecated.
        use options instead
        Create
        Parameters:
        reader - - input
        parseComments - - true to keep the comments

      • ParserImpl

        public ParserImpl​(Scanner scanner)

    • Method Detail

      • checkEvent

        public boolean checkEvent​(Event.ID choice)
        Check the type of the next event.
        Specified by:
        checkEvent in interface Parser
        Parameters:
        choice - Event ID.
        Returns:
        true if the next event can be assigned to a variable of the given type. Returns false if no more events are available.

      • getEvent

        public Event getEvent()
        Get the next event and proceed further.
        Specified by:
        getEvent in interface Parser
        Returns:
        the next parsed event

      • processDirectives

        private VersionTagsTuple processDirectives()
        https://yaml.org/spec/1.1/#id898785 says "If the document specifies no directives, it is parsed using the same settings as the previous document. If the document does specify any directives, all directives of previous documents, if any, are ignored." TODO the last statement is not respected (as in PyYAML, to work the same)
        Returns:
        directives to be applied for the current document

      • parseFlowNode

        private Event parseFlowNode()

      • parseBlockNodeOrIndentlessSequence

        private Event parseBlockNodeOrIndentlessSequence()

      • parseNode

        private Event parseNode​(boolean block,
                        boolean indentlessSequence)

      • processEmptyScalar

        private Event processEmptyScalar​(Mark mark)
         block_mapping     ::= BLOCK-MAPPING_START
           ((KEY block_node_or_indentless_sequence?)?
           (VALUE block_node_or_indentless_sequence?)?)*
           BLOCK-END