class Psych::Parser
YAML event parser class. This class parses aYAML document and calls events on the handler that is passed to the constructor. The events can be used for things such as constructing aYAML AST or deserializingYAML documents. It can even be fed back toPsych::Emitter to emit the same document that was parsed.
SeePsych::Handler for documentation on the events thatPsych::Parser emits.
Here is an example that prints out ever scalar found in aYAML document:
# Handler for detecting scalar valuesclassScalarHandler<Psych::Handlerdefscalarvalue,anchor,tag,plain,quoted,styleputsvalueendendparser =Psych::Parser.new(ScalarHandler.new)parser.parse(yaml_document)
Here is an example that feeds the parser back in toPsych::Emitter. TheYAML document is read from STDIN and written back out to STDERR:
parser =Psych::Parser.new(Psych::Emitter.new($stderr))parser.parse($stdin)
Psych usesPsych::Parser in combination withPsych::TreeBuilder to construct an AST of the parsedYAML document.
Constants
Attributes
Set the encoding for this parser toencoding
The handler on which events will be called
Public Class Methods
Source
# File ext/psych/lib/psych/parser.rb, line 47definitializehandler =Handler.new@handler =handler@external_encoding =ANYend
Creates a newPsych::Parser instance withhandler.YAML events will be called onhandler. SeePsych::Parser for more details.
Public Instance Methods
Source
static VALUE mark(VALUE self){ VALUE mark_klass; VALUE args[3]; yaml_parser_t * parser; TypedData_Get_Struct(self, yaml_parser_t, &psych_parser_type, parser); mark_klass = rb_const_get_at(cPsychParser, rb_intern("Mark")); args[0] = SIZET2NUM(parser->mark.index); args[1] = SIZET2NUM(parser->mark.line); args[2] = SIZET2NUM(parser->mark.column); return rb_class_new_instance(3, args, mark_klass);}Returns aPsych::Parser::Mark object that contains line, column, and index information.
Source
# File ext/psych/lib/psych/parser.rb, line 61defparseyaml,path =yaml.respond_to?(:path)?yaml.path:"<unknown>"_native_parse@handler,yaml,pathend
Parse theYAML document contained inyaml. Events will be called on the handler set on the parser instance.
Private Instance Methods
Source
static VALUE parse(VALUE self, VALUE handler, VALUE yaml, VALUE path){ yaml_parser_t * parser; yaml_event_t event; int done = 0; int state = 0; int parser_encoding = YAML_ANY_ENCODING; int encoding = rb_utf8_encindex(); rb_encoding * internal_enc = rb_default_internal_encoding(); TypedData_Get_Struct(self, yaml_parser_t, &psych_parser_type, parser); yaml_parser_delete(parser); yaml_parser_initialize(parser); if (rb_respond_to(yaml, id_read)) { yaml = transcode_io(yaml, &parser_encoding); yaml_parser_set_encoding(parser, parser_encoding); yaml_parser_set_input(parser, io_reader, (void *)yaml); } else { StringValue(yaml); yaml = transcode_string(yaml, &parser_encoding); yaml_parser_set_encoding(parser, parser_encoding); yaml_parser_set_input_string( parser, (const unsigned char *)RSTRING_PTR(yaml), (size_t)RSTRING_LEN(yaml) ); } while(!done) { VALUE event_args[5]; VALUE start_line, start_column, end_line, end_column; if(parser->error || !yaml_parser_parse(parser, &event)) { VALUE exception; exception = make_exception(parser, path); yaml_parser_delete(parser); yaml_parser_initialize(parser); rb_exc_raise(exception); } start_line = SIZET2NUM(event.start_mark.line); start_column = SIZET2NUM(event.start_mark.column); end_line = SIZET2NUM(event.end_mark.line); end_column = SIZET2NUM(event.end_mark.column); event_args[0] = handler; event_args[1] = start_line; event_args[2] = start_column; event_args[3] = end_line; event_args[4] = end_column; rb_protect(protected_event_location, (VALUE)event_args, &state); switch(event.type) { case YAML_STREAM_START_EVENT: { VALUE args[2]; args[0] = handler; args[1] = INT2NUM(event.data.stream_start.encoding); rb_protect(protected_start_stream, (VALUE)args, &state); } break; case YAML_DOCUMENT_START_EVENT: { VALUE args[4]; /* Get a list of tag directives (if any) */ VALUE tag_directives = rb_ary_new(); /* Grab the document version */ VALUE version = event.data.document_start.version_directive ? rb_ary_new3( (long)2, INT2NUM(event.data.document_start.version_directive->major), INT2NUM(event.data.document_start.version_directive->minor) ) : rb_ary_new(); if(event.data.document_start.tag_directives.start) { yaml_tag_directive_t *start = event.data.document_start.tag_directives.start; yaml_tag_directive_t *end = event.data.document_start.tag_directives.end; for(; start != end; start++) { VALUE handle = Qnil; VALUE prefix = Qnil; if(start->handle) { handle = rb_str_new2((const char *)start->handle); PSYCH_TRANSCODE(handle, encoding, internal_enc); } if(start->prefix) { prefix = rb_str_new2((const char *)start->prefix); PSYCH_TRANSCODE(prefix, encoding, internal_enc); } rb_ary_push(tag_directives, rb_ary_new3((long)2, handle, prefix)); } } args[0] = handler; args[1] = version; args[2] = tag_directives; args[3] = event.data.document_start.implicit == 1 ? Qtrue : Qfalse; rb_protect(protected_start_document, (VALUE)args, &state); } break; case YAML_DOCUMENT_END_EVENT: { VALUE args[2]; args[0] = handler; args[1] = event.data.document_end.implicit == 1 ? Qtrue : Qfalse; rb_protect(protected_end_document, (VALUE)args, &state); } break; case YAML_ALIAS_EVENT: { VALUE args[2]; VALUE alias = Qnil; if(event.data.alias.anchor) { alias = rb_str_new2((const char *)event.data.alias.anchor); PSYCH_TRANSCODE(alias, encoding, internal_enc); } args[0] = handler; args[1] = alias; rb_protect(protected_alias, (VALUE)args, &state); } break; case YAML_SCALAR_EVENT: { VALUE args[7]; VALUE anchor = Qnil; VALUE tag = Qnil; VALUE plain_implicit, quoted_implicit, style; VALUE val = rb_str_new( (const char *)event.data.scalar.value, (long)event.data.scalar.length ); PSYCH_TRANSCODE(val, encoding, internal_enc); if(event.data.scalar.anchor) { anchor = rb_str_new2((const char *)event.data.scalar.anchor); PSYCH_TRANSCODE(anchor, encoding, internal_enc); } if(event.data.scalar.tag) { tag = rb_str_new2((const char *)event.data.scalar.tag); PSYCH_TRANSCODE(tag, encoding, internal_enc); } plain_implicit = event.data.scalar.plain_implicit == 0 ? Qfalse : Qtrue; quoted_implicit = event.data.scalar.quoted_implicit == 0 ? Qfalse : Qtrue; style = INT2NUM(event.data.scalar.style); args[0] = handler; args[1] = val; args[2] = anchor; args[3] = tag; args[4] = plain_implicit; args[5] = quoted_implicit; args[6] = style; rb_protect(protected_scalar, (VALUE)args, &state); } break; case YAML_SEQUENCE_START_EVENT: { VALUE args[5]; VALUE anchor = Qnil; VALUE tag = Qnil; VALUE implicit, style; if(event.data.sequence_start.anchor) { anchor = rb_str_new2((const char *)event.data.sequence_start.anchor); PSYCH_TRANSCODE(anchor, encoding, internal_enc); } tag = Qnil; if(event.data.sequence_start.tag) { tag = rb_str_new2((const char *)event.data.sequence_start.tag); PSYCH_TRANSCODE(tag, encoding, internal_enc); } implicit = event.data.sequence_start.implicit == 0 ? Qfalse : Qtrue; style = INT2NUM(event.data.sequence_start.style); args[0] = handler; args[1] = anchor; args[2] = tag; args[3] = implicit; args[4] = style; rb_protect(protected_start_sequence, (VALUE)args, &state); } break; case YAML_SEQUENCE_END_EVENT: rb_protect(protected_end_sequence, handler, &state); break; case YAML_MAPPING_START_EVENT: { VALUE args[5]; VALUE anchor = Qnil; VALUE tag = Qnil; VALUE implicit, style; if(event.data.mapping_start.anchor) { anchor = rb_str_new2((const char *)event.data.mapping_start.anchor); PSYCH_TRANSCODE(anchor, encoding, internal_enc); } if(event.data.mapping_start.tag) { tag = rb_str_new2((const char *)event.data.mapping_start.tag); PSYCH_TRANSCODE(tag, encoding, internal_enc); } implicit = event.data.mapping_start.implicit == 0 ? Qfalse : Qtrue; style = INT2NUM(event.data.mapping_start.style); args[0] = handler; args[1] = anchor; args[2] = tag; args[3] = implicit; args[4] = style; rb_protect(protected_start_mapping, (VALUE)args, &state); } break; case YAML_MAPPING_END_EVENT: rb_protect(protected_end_mapping, handler, &state); break; case YAML_NO_EVENT: rb_protect(protected_empty, handler, &state); break; case YAML_STREAM_END_EVENT: rb_protect(protected_end_stream, handler, &state); done = 1; break; } yaml_event_delete(&event); if (state) rb_jump_tag(state); } return self;}