private string CheckUri(string uri)
{
string error = Entity.ValidateUri(uri);
if (error != null)
{
OnWarning("The URI <" + uri + "> is not valid: " + error);
}
return(uri);
}
private Resource ReadResource2(ParseContext context, bool allowDirective, out bool reverse, out bool forgetBNode)
{
reverse = false;
forgetBNode = false;
Location loc = context.Location;
object tok = ReadToken(context.source, context);
if (tok is Literal)
{
return((Literal)tok);
}
string str = (string)tok;
if (str == "")
{
return(null);
}
// Directives
if (str == "@prefix")
{
if (allowDirective)
{
return(PrefixResource);
}
else
{
OnError("The directive '" + str + "' is not allowed here", loc);
}
}
if (str == "@keywords")
{
if (allowDirective)
{
return(KeywordsResource);
}
else
{
OnError("The directive '" + str + "' is not allowed here", loc);
}
}
if (str == "@base")
{
if (allowDirective)
{
return(BaseResource);
}
else
{
OnError("The directive '" + str + "' is not allowed here", loc);
}
}
// @ Keywords
if (context.UsingKeywords && context.Keywords.Contains(str))
{
str = "@" + str;
}
if (!context.UsingKeywords &&
(str == "a" || str == "has" || str == "is"))
{
str = "@" + str;
}
// Standard Keywords
// TODO: Turn these off with @keywords
if (str == "@a")
{
return(entRDFTYPE);
}
if (str == "=")
{
return(entDAMLEQUIV);
}
if (str == "=>")
{
return(entLOGIMPLIES);
}
if (str == "<=")
{
reverse = true;
return(entLOGIMPLIES);
}
if (str == "=:>") // SPECIAL EXTENSION!
{
return(entGRAPHCONTAINS);
}
if (str == "@has") // ignore this token
{
return(ReadResource2(context, false, out reverse, out forgetBNode));
}
if (str == "@is")
{
// Reverse predicate
bool reversetemp;
Resource pred = ReadResource2(context, false, out reversetemp, out forgetBNode);
reverse = true;
string of = ReadToken(context.source, context) as string;
if (of == null)
{
OnError("End of stream while expecting 'of'", loc);
}
if (of == "@of" ||
(!context.UsingKeywords && of == "of") ||
(context.UsingKeywords && context.Keywords.Contains("of") && of == "of"))
{
return(pred);
}
OnError("Expecting token 'of' but found '" + of + "'", loc);
return(null); // unreachable
}
if (str.StartsWith("@"))
{
OnError("The " + str + " directive is not supported", loc);
}
// URI
if (str.StartsWith("<") && str.EndsWith(">"))
{
string uri = GetAbsoluteUri(BaseUri, str.Substring(1, str.Length - 2));
string urierror = Entity.ValidateUri(uri);
if (urierror != null)
{
OnWarning(urierror, loc);
}
return(GetResource(context, uri));
}
// VARIABLE
if (str[0] == '?')
{
string name = str.Substring(1);
Entity varb = (Entity)context.variables[name];
if (varb == null)
{
varb = new Variable(name);
AddVariable((Variable)varb);
context.variables[name] = varb;
}
return(varb);
}
// QNAME
if (str.IndexOf(":") != -1)
{
return(ResolveQName(str, context, loc));
}
// ANONYMOUS
if (str == "[")
{
Entity ret = new BNode();
ReadWhitespace(context.source);
if (context.source.Peek() != ']')
{
char bracket = ReadPredicates(ret, context);
if (bracket == '.')
{
bracket = ReadPunc(context.source);
}
if (bracket != ']')
{
OnError("Expected a close bracket but found '" + bracket + "'", loc);
}
}
else
{
context.source.Read();
}
forgetBNode = true;
return(ret);
}
// LIST
if (str == "(")
{
// A list
Entity head = null, ent = null;
while (true)
{
bool rev2, fb2;
Resource res = ReadResource(context, false, out rev2, out fb2);
if (res == null)
{
break;
}
if (ent == null)
{
ent = new BNode();
head = ent;
}
else
{
Entity sub = new BNode();
Add(context.store, new Statement(ent, entRDFREST, sub, context.meta), loc);
ent = sub;
}
Add(context.store, new Statement(ent, entRDFFIRST, res, context.meta), loc);
if (fb2)
{
DoForget(res, context);
}
}
if (head == null) // No list items.
{
head = entRDFNIL; // according to Turtle spec
}
else
{
Add(context.store, new Statement(ent, entRDFREST, entRDFNIL, context.meta), loc);
}
return(head);
}
if (str == ")")
{
return(null); // Should I use a more precise end-of-list return value?
}
// FORMULA
if (str == "{")
{
// ParseContext is a struct, so this gives us a clone.
ParseContext newcontext = context;
// The formula is denoted by a blank node, unless we set
// the override meta flag above.
if (context.overrideMeta == null)
{
newcontext.meta = new BNode();
}
else
{
newcontext.meta = context.overrideMeta;
}
// According to the spec, _:xxx anonymous nodes are
// local to the formula. But ?$variables (which aren't
// mentioned in the spec) are treated as global names.
newcontext.anonymous = new Hashtable();
while (NextPunc(context.source) != '}' && ReadStatement(newcontext))
{
}
ReadWhitespace(context.source);
if (context.source.Peek() == '}')
{
context.source.Read();
}
return(newcontext.meta);
}
// NUMERIC LITERAL
// In Turtle, numbers are restricted to [0-9]+, and are datatyped xsd:integer.
double numval;
#if !SILVERLIGHT
if (double.TryParse(str, System.Globalization.NumberStyles.Any, null, out numval))
{
#else
bool ok = true;
numval = 0;
try {
numval = double.Parse(str);
}
catch (Exception) {
ok = false;
}
if (ok)
{
#endif
if (numval >= long.MinValue && numval <= long.MaxValue && numval == (double)(long)numval)
{
return(new Literal(((long)numval).ToString(), null, NS.XMLSCHEMA + "integer"));
}
else
{
return(new Literal(numval.ToString(), null, NS.XMLSCHEMA + "double"));
}
}
//BOOLEAN LITERAL
if (str == "true" || str == "false")
{
return(new Literal(str, null, NS.XMLSCHEMA + "boolean"));
}
// If @keywords is used, alphanumerics that aren't keywords
// are local names in the default namespace.
if (context.UsingKeywords && char.IsLetter(str[0]))
{
if (BaseUri == null)
{
OnError("The document contains an unqualified name but no BaseUri was specified: \"" + str + "\"", loc);
}
return(GetResource(context, BaseUri + str));
}
// NOTHING MATCHED
OnError("Invalid token: " + str, loc);
return(null);
}