class Psych::Parser
YAML event parser class. This class parses a YAML document and calls events on the handler that is passed to the constructor. The events can be used for things such as constructing a YAML AST or deserializing YAML documents. It can even be fed back to Psych::Emitter to emit the same document that was parsed.
See Psych::Handler for documentation on the events that Psych::Parser emits.
Here is an example that prints out ever scalar found in a YAML document:
# Handler for detecting scalar values class ScalarHandler < Psych::Handler def scalar value, anchor, tag, plain, quoted, style puts value end end parser = Psych::Parser.new(ScalarHandler.new) parser.parse(yaml_document)
Here is an example that feeds the parser back in to Psych::Emitter. The YAML document is read from STDIN and written back out to STDERR:
parser = Psych::Parser.new(Psych::Emitter.new($stderr)) parser.parse($stdin)
Psych uses Psych::Parser in combination with Psych::TreeBuilder to construct an AST of the parsed YAML document.
Constants
Attributes
Set the encoding for this parser to encoding
The handler on which events will be called
Public Class Methods
Source
# File ext/psych/lib/psych/parser.rb, line 47 def initialize handler = Handler.new @handler = handler @external_encoding = ANY end
Creates a new Psych::Parser instance with handler. YAML events will be called on handler. See Psych::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 a Psych::Parser::Mark object that contains line, column, and index information.
Source
# File ext/psych/lib/psych/parser.rb, line 61 def parse yaml, path = yaml.respond_to?(:path) ? yaml.path : "<unknown>" _native_parse @handler, yaml, path end
Parse the YAML document contained in yaml. Events will be called on the handler set on the parser instance.
See Psych::Parser and Psych::Parser#handler
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;
}