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Java > Open Source Codes > polyglot > util > TypeEncoder


1 package polyglot.util;
2
3 import polyglot.main.Report;
4 import polyglot.types.*;
5
6 import java.io.*;
7 import java.util.zip.*;
8
9 /**
10  * The <code>TypeEncoder</code> gives the ability to encode a polyglot
11  * <code>Type</code> as a Java string.
12  * <p>
13  * It uses a form of serialization to encode the <code>Type</code> into
14  * a byte stream and then converts the byte stream to a standard Java string.
15  * <p>
16  * The difference between the encoder and a normal serialization process is
17  * that in order to encode this type, we need to sever any links to other types
18  * in the current environment. So any <code>ClassType</code> other than the
19  * the type being encoded is replaced in the stream with a
20  * <code>PlaceHolder</code> that contains the name of the class. To aid
21  * in the decoding process, placeholders for member classes user their
22  * "mangled" name; non-member classes use their fully qualified name.
23  */
24 public class TypeEncoder
25 {
26   protected TypeSystem ts;
27   protected final boolean zip = true;
28   protected final boolean base64 = true;
29   protected final boolean test = false;
30
31   public TypeEncoder( TypeSystem ts)
32   {
33     this.ts = ts;
34   }
35
36   public String JavaDoc encode( Type t) throws IOException
37   {
38     ByteArrayOutputStream baos;
39     ObjectOutputStream oos;
40
41     if (Report.should_report(Report.serialize, 1)) {
42       Report.report(1, "Encoding type " + t);
43     }
44     
45     baos = new ByteArrayOutputStream();
46
47     if (zip) {
48     oos = new TypeOutputStream( new GZIPOutputStream( baos), ts, t);
49     }
50     else {
51     oos = new TypeOutputStream( baos, ts, t);
52     }
53
54     oos.writeObject( t);
55     oos.flush();
56     oos.close();
57     
58     byte[] b = baos.toByteArray();
59
60     if (Report.should_report(Report.serialize, 2)) {
61       Report.report(2, "Size of serialization (with"
62             + (zip?"":"out") + " zipping) is " + b.length + " bytes");
63     }
64
65     String JavaDoc s;
66     if (base64) {
67         s = new String JavaDoc(Base64.encode(b));
68     }
69     else {
70         StringBuffer JavaDoc sb = new StringBuffer JavaDoc(b.length);
71         for (int i = 0; i < b.length; i++)
72         sb.append((char) b[i]);
73         s = sb.toString();
74     }
75     
76     if (Report.should_report(Report.serialize, 2)) {
77       Report.report(2, "Size of serialization after conversion to string is "
78             + s.length() + " characters");
79     }
80
81     if (test) {
82       // Test it.
83 try {
84     decode(s);
85       }
86       catch (Exception JavaDoc e) {
87         e.printStackTrace();
88     throw new InternalCompilerError(
89         "Could not decode back to " + t + ": " + e.getMessage(), e);
90       }
91     }
92
93     return s;
94   }
95
96   public Type decode(String JavaDoc s) throws InvalidClassException
97   {
98     ObjectInputStream ois;
99     byte[] b;
100
101     if (base64) {
102         b = Base64.decode(s.toCharArray());
103     }
104     else {
105         char[] source;
106         source = s.toCharArray();
107         b = new byte[ source.length];
108         for (int i = 0; i < source.length; i++)
109         b[i] = (byte) source[i];
110     }
111     
112     try {
113         if (zip) {
114             ois = new TypeInputStream( new GZIPInputStream(
115                          new ByteArrayInputStream( b)), ts);
116         }
117         else {
118             ois = new TypeInputStream( new ByteArrayInputStream( b), ts);
119         }
120         return (Type)ois.readObject();
121     }
122     catch (InvalidClassException e) {
123         throw e;
124     }
125     catch (IOException e) {
126         throw new InternalCompilerError("IOException thrown while " +
127             "decoding serialized type info: " + e.getMessage(), e);
128     }
129     catch (ClassNotFoundException JavaDoc e) {
130         throw new InternalCompilerError("Unable to find one of the classes " +
131             "for the serialized type info: " + e.getMessage(), e);
132     }
133   }
134 }
135
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