Util/SemWeb/RdfWriter.cs

   1 using System;
   2 using System.Collections;
   3 using System.IO;
   4
   5 namespace SemWeb {
   6         public abstract class RdfWriter : IDisposable, StatementSink {
   7                 string baseuri;
   8                 bool closed;
   9
  10                 public abstract NamespaceManager Namespaces { get; }
  11
  12                 public string BaseUri {
  13                         get {
  14                                 return baseuri;
  15                         }
  16                         set {
  17                                 baseuri = value;
  18                         }
  19                 }
  20
  21                 protected object GetResourceKey(Resource resource) {
  22                         return resource.GetResourceKey(this);
  23                 }
  24
  25                 protected void SetResourceKey(Resource resource, object value) {
  26                         resource.SetResourceKey(this, value);
  27                 }
  28
  29                 internal static TextWriter GetWriter(string dest) {
  30                         if (dest == "-")
  31                                 return Console.Out;
  32                         return new StreamWriter(dest);
  33                 }
  34
  35                 bool StatementSink.Add(Statement statement) {
  36                         Add(statement);
  37                         return true;
  38                 }
  39
  40                 public void Add(Statement statement) {
  41                         if (statement.AnyNull)
  42                                 throw new ArgumentNullException();
  43
  44                         string s = getUri(statement.Subject);
  45                         string p = getUri(statement.Predicate);
  46
  47                         if (statement.Object is Literal) {
  48                                 Literal lit = (Literal)statement.Object;
  49                                 WriteStatement(s, p, lit);
  50                         } else {
  51                                 string o = getUri((Entity)statement.Object);
  52                                 WriteStatement(s, p, o);
  53                         }
  54                 }
  55
  56                 private string getUri(Entity e) {
  57                         if (e.Uri != null) return e.Uri;
  58                         string uri = (string)GetResourceKey(e);
  59                         if (uri != null) return uri;
  60                         uri = CreateAnonymousEntity();
  61                         SetResourceKey(e, uri);
  62                         return uri;
  63                 }
  64
  65                 public abstract void WriteStatement(string subj, string pred, string obj);
  66
  67                 public abstract void WriteStatement(string subj, string pred, Literal literal);
  68
  69                 public abstract string CreateAnonymousEntity();
  70
  71                 public virtual void Close() {
  72                         if (closed) return;
  73                         closed = true;
  74                 }
  75
  76                 void IDisposable.Dispose() {
  77                         Close();
  78                 }
  79         }
  80 }