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using System;
using System.Collections;
using System.IO;
using System.Text;
using SemWeb;
using SemWeb.Util;
namespace SemWeb {
public class N3Reader : RdfReader {
Resource PrefixResource = new Literal("@prefix");
Resource KeywordsResource = new Literal("@keywords");
TextReader sourcestream;
NamespaceManager namespaces = new NamespaceManager();
Entity entRDFTYPE = "http://www.w3.org/1999/02/22-rdf-syntax-ns#type";
Entity entRDFFIRST = "http://www.w3.org/1999/02/22-rdf-syntax-ns#first";
Entity entRDFREST = "http://www.w3.org/1999/02/22-rdf-syntax-ns#rest";
Entity entRDFNIL = "http://www.w3.org/1999/02/22-rdf-syntax-ns#nil";
//Entity entOWLSAMEAS = "http://www.w3.org/2002/07/owl#sameAs";
Entity entDAMLEQUIV = "http://www.daml.org/2000/12/daml+oil#equivalentTo";
Entity entLOGIMPLIES = "http://www.w3.org/2000/10/swap/log#implies";
bool addFailuresAsWarnings = false;
public N3Reader(TextReader source) {
this.sourcestream = source;
}
public N3Reader(string sourcefile) {
this.sourcestream = GetReader(sourcefile);
BaseUri = "file:" + sourcefile + "#";
}
private struct ParseContext {
public MyReader source;
public StatementSink store;
public NamespaceManager namespaces;
public UriMap namedNode;
public Hashtable anonymous;
public Hashtable variables;
public Entity meta;
public bool UsingKeywords;
public Hashtable Keywords;
public Location Location { get { return new Location(source.Line, source.Col); } }
}
public override void Select(StatementSink store) {
ParseContext context = new ParseContext();
context.source = new MyReader(sourcestream);
context.store = store;
context.namespaces = namespaces;
context.namedNode = new UriMap();
context.anonymous = new Hashtable();
context.variables = new Hashtable();
context.meta = Meta;
while (ReadStatement(context)) { }
}
private bool ReadStatement(ParseContext context) {
Location loc = context.Location;
bool reverse;
Resource subject = ReadResource(context, out reverse);
if (subject == null) return false;
if (reverse) OnError("is...of not allowed on a subject", loc);
if ((object)subject == (object)PrefixResource) {
loc = context.Location;
string qname = ReadToken(context.source, context) as string;
if (qname == null || !qname.EndsWith(":")) OnError("When using @prefix, the prefix identifier must end with a colon", loc);
loc = context.Location;
Resource uri = ReadResource(context, out reverse);
if (uri == null) OnError("Expecting a URI", loc);
if (reverse) OnError("is...of not allowed here", loc);
namespaces.AddNamespace(uri.Uri, qname.Substring(0, qname.Length-1));
loc = context.Location;
char punc = ReadPunc(context.source);
if (punc != '.')
OnError("Expected a period but found '" + punc + "'", loc);
return true;
}
if ((object)subject == (object)KeywordsResource) {
context.UsingKeywords = true;
context.Keywords = new Hashtable();
while (true) {
ReadWhitespace(context.source);
if (context.source.Peek() == '.') {
context.source.Read();
break;
}
loc = context.Location;
string tok = ReadToken(context.source, context) as string;
if (tok == null)
OnError("Expecting keyword names", loc);
context.Keywords[tok] = tok;
}
return true;
}
// It's possible to just assert the presence of an entity
// by following the entity with a period, or a } to end
// a reified context.
if (NextPunc(context.source) == '.') {
context.source.Read();
return true;
}
if (NextPunc(context.source) == '}') {
context.source.Read();
return false; // end of block
}
// Read the predicates for this subject.
char period = ReadPredicates(subject, context);
loc = context.Location;
if (period != '.' && period != '}')
OnError("Expected a period but found '" + period + "'", loc);
if (period == '}') return false;
return true;
}
private char ReadPredicates(Resource subject, ParseContext context) {
char punctuation = ';';
while (punctuation == ';') {
punctuation = ReadPredicate(subject, context);
// if we read a semicolon, we may still be done
// if it's followed by a period (end of statement)
// or bracket (end of bnode), or brace (end of formula, N3).
if (punctuation == ';') {
int npunc = NextPunc(context.source);
if (npunc == (int)'.' || npunc == (int)']' || npunc == (int)'}')
return ReadPunc(context.source);
}
}
return punctuation;
}
private char ReadPredicate(Resource subject, ParseContext context) {
bool reverse;
Location loc = context.Location;
Resource predicate = ReadResource(context, out reverse);
if (predicate == null) OnError("Expecting a predicate", loc);
if (predicate is Literal) OnError("Predicates cannot be literals", loc);
char punctuation = ',';
while (punctuation == ',') {
ReadObject(subject, (Entity)predicate, context, reverse);
loc = context.Location;
punctuation = ReadPunc(context.source);
}
if (punctuation != '.' && punctuation != ';' && punctuation != ']' && punctuation != '}')
OnError("Expecting a period, semicolon, comma, close-bracket, or close-brace but found '" + punctuation + "'", loc);
return punctuation;
}
private void ReadObject(Resource subject, Entity predicate, ParseContext context, bool reverse) {
bool reverse2;
Location loc = context.Location;
Resource value = ReadResource(context, out reverse2);
if (value == null) OnError("Expecting a resource or literal object", loc);
if (reverse2) OnError("is...of not allowed on objects", loc);
loc = context.Location;
if (!reverse) {
if (subject is Literal) OnError("Subjects of statements cannot be literals", loc);
Add(context.store, new Statement((Entity)subject, predicate, value, context.meta), loc);
} else {
if (value is Literal) OnError("A literal cannot be the object of a reverse-predicate statement", loc);
Add(context.store, new Statement((Entity)value, predicate, subject, context.meta), loc);
}
}
private void ReadWhitespace(MyReader source) {
while (true) {
while (char.IsWhiteSpace((char)source.Peek()))
source.Read();
if (source.Peek() == '#') {
while (true) {
int c = source.Read();
if (c == -1 || c == 10 || c == 13) break;
}
continue;
}
break;
}
}
private char ReadPunc(MyReader source) {
ReadWhitespace(source);
int c = source.Read();
if (c == -1)
OnError("End of file expecting punctuation", new Location(source.Line, source.Col));
return (char)c;
}
private int NextPunc(MyReader source) {
ReadWhitespace(source);
return source.Peek();
}
private void ReadEscapedChar(char c, StringBuilder b, MyReader source, Location loc) {
if (c == 'n') b.Append('\n');
else if (c == 'r') b.Append('\r');
else if (c == 't') b.Append('\t');
else if (c == '\\') b.Append('\\');
else if (c == '"') b.Append('"');
else if (c == '\'') b.Append('\'');
else if (c == 'a') b.Append('\a');
else if (c == 'b') b.Append('\b');
else if (c == 'f') b.Append('\f');
else if (c == 'v') b.Append('\v');
else if (c == '\n') { }
else if (c == '\r') { }
else if (c == 'u' || c == 'U') {
StringBuilder num = new StringBuilder();
if (c == 'u') {
num.Append((char)source.Read()); // four hex digits
num.Append((char)source.Read());
num.Append((char)source.Read());
num.Append((char)source.Read());
} else {
source.Read(); // two zeros
source.Read();
num.Append((char)source.Read()); // six hex digits
num.Append((char)source.Read());
num.Append((char)source.Read());
num.Append((char)source.Read());
num.Append((char)source.Read());
num.Append((char)source.Read());
}
int unicode = int.Parse(num.ToString(), System.Globalization.NumberStyles.AllowHexSpecifier);
b.Append((char)unicode); // is this correct?
} else if (char.IsDigit((char)c) || c == 'x')
OnError("Octal and hex byte-value escapes are deprecated and not supported", loc);
else
OnError("Unrecognized escape character: " + (char)c, loc);
}
private StringBuilder readTokenBuffer = new StringBuilder();
private object ReadToken(MyReader source, ParseContext context) {
ReadWhitespace(source);
Location loc = new Location(source.Line, source.Col);
int firstchar = source.Read();
if (firstchar == -1)
return "";
StringBuilder b = readTokenBuffer; readTokenBuffer.Length = 0;
b.Append((char)firstchar);
if (firstchar == '<') {
// This is a URI or the <= verb. URIs can be escaped like strings, at least in the NTriples spec.
bool escaped = false;
while (true) {
int c = source.Read();
if (c == -1) OnError("Unexpected end of stream within a token beginning with <", loc);
if (b.Length == 2 && c == '=')
return "<="; // the <= verb
if (escaped) {
ReadEscapedChar((char)c, b, source, loc);
escaped = false;
} else if (c == '\\') {
escaped = true;
} else {
b.Append((char)c);
if (c == '>') // end of the URI
break;
}
}
} else if (firstchar == '"') {
// A string: ("""[^"\\]*(?:(?:\\.|"(?!""))[^"\\]*)*""")|("[^"\\]*(?:\\.[^"\\]*)*")
// What kind of crazy regex is this??
b.Length = 0; // get rid of the open quote
bool escaped = false;
bool triplequoted = false;
while (true) {
int c = source.Read();
if (c == -1) OnError("Unexpected end of stream within a string", loc);
if (b.Length == 0 && c == (int)'"' && source.Peek() == (int)'"') {
triplequoted = true;
source.Read();
continue;
}
if (!escaped && c == '\\')
escaped = true;
else if (escaped) {
ReadEscapedChar((char)c, b, source, loc);
escaped = false;
} else {
if (c == '"' && !triplequoted)
break;
if (c == '"' && source.Peek() == '"' && source.Peek2() == '"' && triplequoted)
break;
b.Append((char)c);
}
}
if (triplequoted) { // read the extra end quotes
source.Read();
source.Read();
}
string litvalue = b.ToString();
string litlang = null;
string litdt = null;
// Strings can be suffixed with @langcode or ^^symbol (but not both?).
if (source.Peek() == '@') {
source.Read();
b.Length = 0;
while (char.IsLetterOrDigit((char)source.Peek()) || source.Peek() == (int)'-')
b.Append((char)source.Read());
litlang = b.ToString();
} else if (source.Peek() == '^' && source.Peek2() == '^') {
loc = new Location(source.Line, source.Col);
source.Read();
source.Read();
litdt = ReadToken(source, context).ToString(); // better be a string URI
if (litdt.StartsWith("<") && litdt.EndsWith(">"))
litdt = litdt.Substring(1, litdt.Length-2);
else if (litdt.IndexOf(":") != -1) {
Resource r = ResolveQName(litdt, context, loc);
if (r.Uri == null)
OnError("A literal datatype cannot be an anonymous entity", loc);
litdt = r.Uri;
}
}
return new Literal(litvalue, litlang, litdt);
} else if (char.IsLetter((char)firstchar) || firstchar == '?' || firstchar == '@' || firstchar == ':' || firstchar == '_') {
// Something starting with @
// A QName: ([a-zA-Z_][a-zA-Z0-9_]*)?:)?([a-zA-Z_][a-zA-Z0-9_]*)?
// A variable: \?[a-zA-Z_][a-zA-Z0-9_]*
while (true) {
int c = source.Peek();
if (c == -1 || (!char.IsLetterOrDigit((char)c) && c != '-' && c != '_' && c != ':')) break;
b.Append((char)source.Read());
}
} else if (char.IsDigit((char)firstchar) || firstchar == '+' || firstchar == '-') {
while (true) {
int ci = source.Peek();
if (ci == -1) break;
if (ci == ']' || ci == ')' || ci == '}') break;
// punctuation followed by a space means the punctuation is
// punctuation, and not part of this token
if (!char.IsDigit((char)ci) && source.Peek2() != -1 && char.IsWhiteSpace((char)source.Peek2()))
break;
char c = (char)ci;
if (char.IsWhiteSpace(c)) break;
b.Append((char)source.Read());
}
} else if (firstchar == '=') {
if (source.Peek() == (int)'>')
b.Append((char)source.Read());
} else if (firstchar == '[') {
// The start of an anonymous node.
} else if (firstchar == '{') {
return "{";
} else if (firstchar == '(') {
return "(";
} else if (firstchar == ')') {
return ")";
} else {
while (true) {
int c = source.Read();
if (c == -1) break;
if (char.IsWhiteSpace((char)c)) break;
b.Append((char)c);
}
OnError("Invalid token: " + b.ToString(), loc);
}
return b.ToString();
}
private Resource ReadResource(ParseContext context, out bool reverse) {
Location loc = context.Location;
Resource res = ReadResource2(context, out reverse);
ReadWhitespace(context.source);
while (context.source.Peek() == '!' || context.source.Peek() == '^' || (context.source.Peek() == '.' && context.source.Peek2() != -1 && char.IsLetter((char)context.source.Peek2())) ) {
int pathType = context.source.Read();
bool reverse2;
loc = context.Location;
Resource path = ReadResource2(context, out reverse2);
if (reverse || reverse2) OnError("is...of is not allowed in path expressions", loc);
if (!(path is Entity)) OnError("A path expression cannot be a literal", loc);
Entity anon = new BNode();
Statement s;
if (pathType == '!' || pathType == '.') {
if (!(res is Entity)) OnError("A path expression cannot contain a literal: " + res, loc);
s = new Statement((Entity)res, (Entity)path, anon, context.meta);
} else {
s = new Statement(anon, (Entity)path, res, context.meta);
}
Add(context.store, s, loc);
res = anon;
ReadWhitespace(context.source);
}
return res;
}
private Entity GetResource(ParseContext context, string uri) {
if (!ReuseEntities)
return new Entity(uri);
Entity ret = (Entity)context.namedNode[uri];
if (ret != null) return ret;
ret = new Entity(uri);
context.namedNode[uri] = ret;
return ret;
}
private Resource ResolveQName(string str, ParseContext context, Location loc) {
int colon = str.IndexOf(":");
string prefix = str.Substring(0, colon);
if (prefix == "_") {
Resource ret = (Resource)context.anonymous[str];
if (ret == null) {
ret = new BNode(str.Substring(colon+1));
context.anonymous[str] = ret;
}
return ret;
} else if (prefix == "" && context.namespaces.GetNamespace(prefix) == null) {
return GetResource(context, (BaseUri == null ? "#" : BaseUri) + str.Substring(colon+1));
} else {
string ns = context.namespaces.GetNamespace(prefix);
if (ns == null)
OnError("Prefix is undefined: " + str, loc);
if (prefix != "")
Namespaces.AddNamespace(ns, prefix);
return GetResource(context, ns + str.Substring(colon+1));
}
}
private Resource ReadResource2(ParseContext context, out bool reverse) {
reverse = 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;
// @ Keywords
if (str == "@prefix")
return PrefixResource;
if (str == "@keywords")
return KeywordsResource;
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 == "@has") // ignore this token
return ReadResource2(context, out reverse);
if (str == "@is") {
// Reverse predicate
bool reversetemp;
Resource pred = ReadResource2(context, out reversetemp);
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));
return GetResource(context, uri);
}
// VARIABLE
if (str[0] == '?') {
string name = str.Substring(1);
Entity var = (Entity)context.variables[name];
if (var == null) {
var = new Variable(name);
AddVariable((Variable)var);
context.variables[name] = var;
}
return var;
}
// 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();
}
return ret;
}
// LIST
if (str == "(") {
// A list
Entity ent = null;
while (true) {
bool rev2;
Resource res = ReadResource(context, out rev2);
if (res == null)
break;
if (ent == null) {
ent = new BNode();
} 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 (ent == null) // No list items.
ent = entRDFNIL; // according to Turtle spec
else
Add(context.store, new Statement(ent, entRDFREST, entRDFNIL, context.meta), loc);
return ent;
}
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
newcontext.meta = new BNode();
// 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 (double.TryParse(str, System.Globalization.NumberStyles.Any, null, out numval))
return new Literal(numval.ToString());
// 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;
}
private void Add(StatementSink store, Statement statement, Location position) {
try {
store.Add(statement);
} catch (Exception e) {
if (!addFailuresAsWarnings)
OnError("Add failed on statement { " + statement + " }: " + e.Message, position, e);
else
OnWarning("Add failed on statement { " + statement + " }: " + e.Message, position, e);
}
}
private void OnError(string message, Location position) {
throw new ParserException(message + ", line " + position.Line + " col " + position.Col);
}
private void OnError(string message, Location position, Exception cause) {
throw new ParserException(message + ", line " + position.Line + " col " + position.Col, cause);
}
private void OnWarning(string message, Location position, Exception cause) {
OnWarning(message + ", line " + position.Line + " col " + position.Col);
}
}
internal class MyReader {
TextReader r;
public MyReader(TextReader reader) { r = reader; }
public int Line = 1;
public int Col = 0;
int[] peeked = new int[2];
int peekCount = 0;
public Location Location { get { return new Location(Line, Col); } }
public int Peek() {
if (peekCount == 0) {
peeked[0] = r.Read();
peekCount = 1;
}
return peeked[0];
}
public int Peek2() {
Peek();
if (peekCount == 1) {
peeked[1] = r.Read();
peekCount = 2;
}
return peeked[1];
}
public int Read() {
int c;
if (peekCount > 0) {
c = peeked[0];
peeked[0] = peeked[1];
peekCount--;
} else {
c = r.Read();
}
if (c == '\n') { Line++; Col = 0; }
else { Col++; }
return c;
}
}
internal struct Location {
public readonly int Line, Col;
public Location(int line, int col) { Line = line; Col = col; }
}
}
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