added a decoder class for Bencoding

git-svn-id: https://svn.berlios.de/svnroot/repos/yacy/trunk@6544 6c8d7289-2bf4-0310-a012-ef5d649a1542

source/net/yacy/kelondro/util/BDecoder.java

@@ -0,0 +1,250 @@
+// BDecoder.java
+// -----------------------
+// part of YaCy
+// (C) by Michael Peter Christen; mc@yacy.net
+// first published on http://www.anomic.de
+// Frankfurt, Germany, 2010
+// Created 03.01.2010
+//
+// this is an BDecoder implementation according to http://wiki.theory.org/BitTorrentSpecification
+//
+// This program is free software; you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation; either version 2 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program; if not, write to the Free Software
+// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
+
+package net.yacy.kelondro.util;
+
+import java.io.File;
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.LinkedHashMap;
+import java.util.List;
+import java.util.Map;
+
+public class BDecoder {
+
+    private byte[] b;
+    private int pos;
+
+    public BDecoder(byte[] b) {
+        this.b = b;
+        this.pos = 0;
+    }
+
+    public enum BType {
+        string, integer, list, dictionary;
+    }
+
+    public interface BObject {
+        public BType getType();
+        public String getString();
+        public long getInteger();
+        public List<BObject> getList();
+        public Map<String, BObject> getMap();
+        public String toString();
+    }
+
+    public class BDfltObject implements BObject {
+
+        public long getInteger() {
+            throw new UnsupportedOperationException();
+        }
+
+        public List<BObject> getList() {
+            throw new UnsupportedOperationException();
+        }
+
+        public Map<String, BObject> getMap() {
+            throw new UnsupportedOperationException();
+        }
+
+        public String getString() {
+            throw new UnsupportedOperationException();
+        }
+
+        public BType getType() {
+            throw new UnsupportedOperationException();
+        }
+
+        public String toString() {
+            throw new UnsupportedOperationException();
+        }
+
+    }
+
+    public class BStringObject extends BDfltObject implements BObject {
+        String s;
+        public BStringObject(String s) {
+            this.s = s;
+        }
+        public BType getType() {
+            return BType.string;
+        }
+        public String getString() {
+            return this.s;
+        }
+        public String toString() {
+            return this.s;
+        }
+    }
+
+    public class BListObject extends BDfltObject implements BObject {
+        List<BObject> l;
+        public BListObject(List<BObject> l) {
+            this.l = l;
+        }
+        public BType getType() {
+            return BType.list;
+        }
+        public List<BObject> getList() {
+            return this.l;
+        }
+        public String toString() {
+            StringBuilder s = new StringBuilder();
+            s.append("[");
+            for (BObject o: l) s.append(o.toString()).append(",");
+            s.setLength(s.length() - 1);
+            s.append("]");
+            return s.toString();
+        }
+    }
+
+    public class BDictionaryObject extends BDfltObject implements BObject {
+        Map<String, BObject> m;
+        public BDictionaryObject(Map<String, BObject> m) {
+            this.m = m;
+        }
+        public BType getType() {
+            return BType.dictionary;
+        }
+        public Map<String, BObject> getMap() {
+            return this.m;
+        }
+        public String toString() {
+            StringBuilder s = new StringBuilder();
+            s.append("{");
+            for (Map.Entry<String, BObject> e: m.entrySet()) s.append(e.getKey()).append(":").append(e.getValue().toString()).append(","); 
+            s.setLength(s.length() - 1);
+            s.append("}");
+            return s.toString();
+        }
+    }
+
+    public class BIntegerObject extends BDfltObject implements BObject {
+        long i;
+        public BIntegerObject(long i) {
+            this.i = i;
+        }
+        public BType getType() {
+            return BType.integer;
+        }
+        public long getInteger() {
+            return this.i;
+        }
+        public String toString() {
+            return Long.toString(this.i);
+        }
+    }
+
+    private Map<String, BObject> convertToMap(final List<BObject> list) {
+        final Map<String, BObject> m = new LinkedHashMap<String, BObject>();
+        final int length = list.size();
+        for (int i = 0; i < length; i += 2) {
+            final String key = list.get(i).getString();
+            BObject value = null;
+            if (i + 1 < length) {
+                value = list.get(i + 1);
+            }
+            m.put(key, value);
+        }
+        return m;
+    }
+
+    private List<BObject> readList() {
+        final List<BObject> list = new ArrayList<BObject>();
+        char ch = (char) b[pos];
+        while (ch != 'e') {
+            BObject bo = parse();
+            if (bo == null) {pos++; break;}
+            list.add(bo);
+            ch = (char) b[pos];
+        }
+        pos++;
+        return list;
+    }
+
+    public BObject parse() {
+        if (pos >= b.length) return null;
+        char ch = (char) b[pos];
+        if ((ch >= '0') && (ch <= '9')) {
+            int end = pos;
+            end++;
+            while (b[end] != ':') ++end;
+            final int len = Integer.parseInt(new String(b, pos, end - pos));
+            final String str = new String(b, end + 1, len);
+            pos = end + len + 1;
+            return new BStringObject(str);
+        } else if (ch == 'l') {
+            pos++;
+            return new BListObject(readList());
+        } else if (ch == 'd') {
+            pos++;
+            return new BDictionaryObject(convertToMap(readList()));
+        } else if (ch == 'i') {
+            pos++;
+            int end = pos;
+            while (b[end] != 'e') ++end;
+            BIntegerObject io = new BIntegerObject(Long.parseLong(new String(b, pos, end - pos)));
+            pos = end + 1;
+            return io;
+        } else {
+            return null;
+        }
+    }
+
+    public static void print(BObject bo, int t) {
+        for (int i = 0; i < t; i++) System.out.print(" ");
+        if (bo.getType() == BType.integer) System.out.println(bo.getInteger());
+        if (bo.getType() == BType.string) System.out.println(bo.getString());
+        if (bo.getType() == BType.list) {
+            System.out.println("[");
+            //for (int i = 0; i < t + 1; i++) System.out.print(" ");
+            for (BObject o: bo.getList()) print(o, t + 1);
+            for (int i = 0; i < t; i++) System.out.print(" ");
+            System.out.println("]");
+        }
+        if (bo.getType() == BType.dictionary) {
+            System.out.println("{");
+            for (Map.Entry<String, BObject> e: bo.getMap().entrySet()) {
+                for (int i = 0; i < t + 1; i++) System.out.print(" ");
+                System.out.print(e.getKey());
+                System.out.println(":");
+                print(e.getValue(), t + 2);
+            }
+            for (int i = 0; i < t; i++) System.out.print(" ");
+            System.out.println("}");
+        }
+    }
+
+    public static void main(String[] args) {
+        try {
+            byte[] b = FileUtils.read(new File(args[0]));
+            BDecoder bdecoder = new BDecoder(b);
+            BObject o = bdecoder.parse();
+            print(o, 0);
+            System.out.println("Object: " + o.toString());
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
+}