NamespaceBinding


1   // Copyright (c) 2003, 2006  Per M.A. Bothner.
2   // This is free software;  for terms and warranty disclaimer see ./COPYING.
3   
4   package gnu.xml;
5   import java.io.*;
6   
7   /** A "namespace node" as a link in a linked list.
8    *
9    * The list may contain duplicates - i.e. multiple namespace bindings
10   * for the same prefix but (usually) different uris.  In that case the
11   * first binding "wins".  One reason for allowing duplicates it to allow
12   * sharing of the lists between a child and its parent element.
13   */
14  
15  public final class NamespaceBinding implements Externalizable
16  {
17    /** Namespace prefix.  An interned String.
18     * A default namespace declaration is represented using null. */
19    public final String   getPrefix () { return prefix; }
20    public final void setPrefix (String   prefix) { this.prefix = prefix; }
21    String   prefix;
22  
23    /** Namespace uri.  An interned String.
24     * The value null "undeclares" any following namespaces; it corresponds
25     * to an empty uri as in the XML Namespaces 1.1 Candidate Recommendation. */
26    public final String   getUri () { return uri; }
27    public final void setUri (String   uri) { this.uri = uri; }
28    String   uri;
29  
30    NamespaceBinding next;
31  
32    int depth;
33  
34    public final NamespaceBinding getNext () { return next; }
35    public final void setNext (NamespaceBinding next)
36    {
37      this.next = next;
38      this.depth = next == null ? 0 : next.depth + 1;
39    }
40  
41    /** Chain the first list in front of the second list.
42     * (The name {@code nconc} comes from Common Lisp.)
43     */
44    public final static NamespaceBinding
45    nconc (NamespaceBinding list1, NamespaceBinding list2)
46    {
47      if (list1 == null)
48        return list2;
49      list1.setNext(nconc(list1.next, list2));
50      return list1;
51    }
52  
53    //  public NamespaceBinding () { }
54  
55    public NamespaceBinding (String   prefix, String   uri, NamespaceBinding next)
56    {
57      this.prefix = prefix;
58      this.uri = uri;
59      setNext(next);
60    }
61  
62    public static final String   XML_NAMESPACE
63    = "http://www.w3.org/XML/1998/namespace";
64  
65    public static final NamespaceBinding predefinedXML
66    = new NamespaceBinding("xml", XML_NAMESPACE, null);
67  
68    /** Resolve a prefix.
69     * @param prefix an interned namespace prefix to search for.
70     * @return a uri or null if not bound
71     */
72    public String   resolve (String   prefix)
73    {
74      for (NamespaceBinding ns = this;  ns != null;  ns = ns.next)
75        {
76      if (ns.prefix == prefix)
77        return ns.uri;
78        }
79      return null;
80    }
81  
82    /** Resolve a prefix, in the initial part of this list.
83     * @param prefix an interned namespace prefix to search for.
84     * @param fencePost only search this list until then.
85     * @return a uri or null if not bound
86     */
87    public String   resolve (String   prefix, NamespaceBinding fencePost)
88    {
89      for (NamespaceBinding ns = this;  ns != fencePost;  ns = ns.next)
90        {
91      if (ns.prefix == prefix)
92        return ns.uri;
93        }
94      return null;
95    }
96  
97    public static NamespaceBinding commonAncestor (NamespaceBinding ns1,
98                           NamespaceBinding ns2)
99    {
100     if (ns1.depth > ns2.depth)
101       {
102     NamespaceBinding tmp = ns1;
103     ns1 = ns2;
104     ns2 = tmp;
105       }
106     while (ns2.depth > ns1.depth)
107       ns2 = ns2.next;
108     while (ns1 != ns2)
109       {
110     ns1 = ns1.next;
111     ns2 = ns2.next;
112       }
113     return ns1; 
114   }
115 
116   /* For debugging:
117   void check ()
118   {
119     NamespaceBinding ns = this;
120     int d = depth;
121     for (;;)
122       {
123     if (ns == null)
124       throw new Error("null ns");
125     if (ns.depth != d)
126       throw new Error("bad depth "+ns.depth+" shoudl be "+d);
127     ns = ns.next;
128     if (ns == null && d == 0)
129       return;
130     d--;
131       }
132   }
133   */
134 
135   /** Reverse the chain, until a fencePost. */
136   public NamespaceBinding reversePrefix (NamespaceBinding fencePost)
137   {
138     NamespaceBinding prev = fencePost;
139     NamespaceBinding t = this;
140     int depth = fencePost == null ? -1 : fencePost.depth;
141     while (t != fencePost)
142       {
143     NamespaceBinding next = t.next;
144     t.next = prev;
145     prev = t;
146     t.depth = ++depth;
147     t = next;
148       }
149     return prev;
150   }
151 
152   /** Return the number of bindings before the <code>fencePost</code>. */
153   public int count (NamespaceBinding fencePost)
154   {
155     int count = 0;
156     for (NamespaceBinding ns = this;  ns != fencePost;  ns = ns.next)
157       count++;
158     return count;
159   }
160 
161   /** Append a new NamespaceBinding if not redundant. */
162   public static NamespaceBinding maybeAdd(String   prefix, String   uri,
163                       NamespaceBinding bindings)
164   {
165     if (bindings == null)
166       {
167     if (uri == null)
168       return bindings;
169     bindings = predefinedXML;
170       }
171     String   found = bindings.resolve(prefix);
172     if (found == null ? uri == null : found.equals(uri))
173       return bindings;
174     return new NamespaceBinding(prefix, uri, bindings);
175   }
176 
177   /** Return a String showing just a single namespace binding. */
178   public String   toString()
179   {
180     return "Namespace{"+prefix+"="+uri+", depth:"+depth+"}";
181   }
182 
183   /** Return a String showing the full namespace binding list. */
184   public String   toStringAll()
185   {
186     StringBuffer   sbuf = new StringBuffer  ("Namespaces{");
187     for (NamespaceBinding ns = this;  ns != null;  ns = ns.next)
188       {
189     sbuf.append(ns.prefix);
190     sbuf.append("=\"");
191     sbuf.append(ns.uri);
192     sbuf.append(ns == null ? "\"" : "\", ");
193       }
194     sbuf.append('}');
195     return sbuf.toString();
196   }
197 
198   public void writeExternal(ObjectOutput out) throws IOException
199   {
200     out.writeUTF(prefix);
201     out.writeUTF(uri);
202     out.writeObject(next);
203   }
204 
205   public void readExternal(ObjectInput in)
206     throws IOException, ClassNotFoundException  
207   {
208     prefix = in.readUTF();
209     uri = in.readUTF();
210     next = (NamespaceBinding) in.readObject();
211   }
212 
213 }
214
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