org.yaml.snakeyaml.parser

Class ParserImpl

java.lang.Object

org.yaml.snakeyaml.parser.ParserImpl

All Implemented Interfaces:

Parser

public class ParserImpl
extends 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.

Field Summary

Fields

Modifier and Type	Field and Description
protected Scanner	scanner

Constructor Summary

Constructors

Constructor and Description
ParserImpl(Scanner scanner)
ParserImpl(StreamReader reader)

Method Summary

Methods

Modifier and Type	Method and Description
boolean	checkEvent(Event.ID choice) Check the type of the next event.
Event	getEvent() Get the next event and proceed further.
Event	peekEvent() Get the next event.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

scanner

protected final Scanner scanner

Constructor Detail

ParserImpl

public ParserImpl(StreamReader reader)

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.

peekEvent

public Event peekEvent()

Get the next event.

Specified by:

peekEvent in interface Parser

Returns:

The event that will be returned on the next call to Parser.getEvent()

getEvent

public Event getEvent()

Get the next event and proceed further.

Specified by:

getEvent in interface Parser