Class: Psych::Parser

Inherits:
Object show all
Defined in:
lib/psych/parser.rb,
psych_parser.c

Overview

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.

Defined Under Namespace

Classes: Mark

Constant Summary collapse

ANY =

Let the parser choose the encoding

Any encoding
UTF8 =

UTF-8 Encoding

INT2NUM(YAML_UTF8_ENCODING)
UTF16LE =

UTF-16-LE Encoding with BOM

INT2NUM(YAML_UTF16LE_ENCODING)
UTF16BE =

UTF-16-BE Encoding with BOM

INT2NUM(YAML_UTF16BE_ENCODING)

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(handler = Handler.new) ⇒ Parser

Creates a new Psych::Parser instance with handler. YAML events will be called on handler. See Psych::Parser for more details.


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# File 'lib/psych/parser.rb', line 46

def initialize handler = Handler.new
  @handler = handler
  @external_encoding = ANY
end

Instance Attribute Details

#external_encoding=(value) ⇒ Object (writeonly)

Set the encoding for this parser to encoding


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# File 'lib/psych/parser.rb', line 40

def external_encoding=(value)
  @external_encoding = value
end

#handlerObject

The handler on which events will be called


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# File 'lib/psych/parser.rb', line 37

def handler
  @handler
end

Instance Method Details

#markObject

Returns a Psych::Parser::Mark object that contains line, column, and index information.


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# File 'psych_parser.c', line 523

static VALUE mark(VALUE self)
{
    VALUE mark_klass;
    VALUE args[3];
    yaml_parser_t * parser;

    Data_Get_Struct(self, yaml_parser_t, parser);
    mark_klass = rb_const_get_at(cPsychParser, rb_intern("Mark"));
    args[0] = INT2NUM(parser->mark.index);
    args[1] = INT2NUM(parser->mark.line);
    args[2] = INT2NUM(parser->mark.column);

    return rb_class_new_instance(3, args, mark_klass);
}

#parse(yaml) ⇒ Object

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


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# File 'psych_parser.c', line 229

static VALUE parse(int argc, VALUE *argv, VALUE self)
{
    VALUE yaml, path;
    yaml_parser_t * parser;
    yaml_event_t event;
    int done = 0;
    int tainted = 0;
    int state = 0;
    int parser_encoding = YAML_ANY_ENCODING;
#ifdef HAVE_RUBY_ENCODING_H
    int encoding = rb_utf8_encindex();
    rb_encoding * internal_enc = rb_default_internal_encoding();
#endif
    VALUE handler = rb_iv_get(self, "@handler");

    if (rb_scan_args(argc, argv, "11", &yaml, &path) == 1) {
  if(rb_respond_to(yaml, id_path))
      path = rb_funcall(yaml, id_path, 0);
  else
      path = rb_str_new2("<unknown>");
    }

    Data_Get_Struct(self, yaml_parser_t, parser);

    yaml_parser_delete(parser);
    yaml_parser_initialize(parser);

    if (OBJ_TAINTED(yaml)) tainted = 1;

    if (rb_respond_to(yaml, id_read)) {
#ifdef HAVE_RUBY_ENCODING_H
  yaml = transcode_io(yaml, &parser_encoding);
  yaml_parser_set_encoding(parser, parser_encoding);
#endif
  yaml_parser_set_input(parser, io_reader, (void *)yaml);
  if (RTEST(rb_obj_is_kind_of(yaml, rb_cIO))) tainted = 1;
    } else {
  StringValue(yaml);
#ifdef HAVE_RUBY_ENCODING_H
  yaml = transcode_string(yaml, &parser_encoding);
  yaml_parser_set_encoding(parser, parser_encoding);
#endif
  yaml_parser_set_input_string(
    parser,
    (const unsigned char *)RSTRING_PTR(yaml),
    (size_t)RSTRING_LEN(yaml)
    );
    }

    while(!done) {
  if(!yaml_parser_parse(parser, &event)) {
      VALUE exception;

      exception = make_exception(parser, path);
      yaml_parser_delete(parser);
      yaml_parser_initialize(parser);

      rb_exc_raise(exception);
  }

  switch(event.type) {
      case YAML_STREAM_START_EVENT:
        {
      VALUE args[2];

      args[0] = handler;
      args[1] = INT2NUM((long)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((long)event.data.document_start.version_directive->major),
      INT2NUM((long)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);
          if (tainted) OBJ_TAINT(handle);
#ifdef HAVE_RUBY_ENCODING_H
          PSYCH_TRANSCODE(handle, encoding, internal_enc);
#endif
      }

      if(start->prefix) {
          prefix = rb_str_new2((const char *)start->prefix);
          if (tainted) OBJ_TAINT(prefix);
#ifdef HAVE_RUBY_ENCODING_H
          PSYCH_TRANSCODE(prefix, encoding, internal_enc);
#endif
      }

      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);
        if (tainted) OBJ_TAINT(alias);
#ifdef HAVE_RUBY_ENCODING_H
        PSYCH_TRANSCODE(alias, encoding, internal_enc);
#endif
    }

    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
        );
    if (tainted) OBJ_TAINT(val);

#ifdef HAVE_RUBY_ENCODING_H
    PSYCH_TRANSCODE(val, encoding, internal_enc);
#endif

    if(event.data.scalar.anchor) {
        anchor = rb_str_new2((const char *)event.data.scalar.anchor);
        if (tainted) OBJ_TAINT(anchor);
#ifdef HAVE_RUBY_ENCODING_H
        PSYCH_TRANSCODE(anchor, encoding, internal_enc);
#endif
    }

    if(event.data.scalar.tag) {
        tag = rb_str_new2((const char *)event.data.scalar.tag);
        if (tainted) OBJ_TAINT(tag);
#ifdef HAVE_RUBY_ENCODING_H
        PSYCH_TRANSCODE(tag, encoding, internal_enc);
#endif
    }

    plain_implicit =
        event.data.scalar.plain_implicit == 0 ? Qfalse : Qtrue;

    quoted_implicit =
        event.data.scalar.quoted_implicit == 0 ? Qfalse : Qtrue;

    style = INT2NUM((long)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);
        if (tainted) OBJ_TAINT(anchor);
#ifdef HAVE_RUBY_ENCODING_H
        PSYCH_TRANSCODE(anchor, encoding, internal_enc);
#endif
    }

    tag = Qnil;
    if(event.data.sequence_start.tag) {
        tag = rb_str_new2((const char *)event.data.sequence_start.tag);
        if (tainted) OBJ_TAINT(tag);
#ifdef HAVE_RUBY_ENCODING_H
        PSYCH_TRANSCODE(tag, encoding, internal_enc);
#endif
    }

    implicit =
        event.data.sequence_start.implicit == 0 ? Qfalse : Qtrue;

    style = INT2NUM((long)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);
        if (tainted) OBJ_TAINT(anchor);
#ifdef HAVE_RUBY_ENCODING_H
        PSYCH_TRANSCODE(anchor, encoding, internal_enc);
#endif
    }

    if(event.data.mapping_start.tag) {
        tag = rb_str_new2((const char *)event.data.mapping_start.tag);
        if (tainted) OBJ_TAINT(tag);
#ifdef HAVE_RUBY_ENCODING_H
        PSYCH_TRANSCODE(tag, encoding, internal_enc);
#endif
    }

    implicit =
        event.data.mapping_start.implicit == 0 ? Qfalse : Qtrue;

    style = INT2NUM((long)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;
}