Preserve source map key order for torrent files (#6)

* Preserve source map key order

* added specific tests for LinkedHashMap ordering

Author: TheLQ

src/main/java/com/dampcake/bencode/BencodeInputStream.java

@@ -23,9 +23,9 @@
 import java.io.PushbackInputStream;
 import java.nio.charset.Charset;
 import java.util.ArrayList;
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
-import java.util.TreeMap;
 
 /**
  * InputStream for reading bencoded data.
@@ -190,7 +190,7 @@ public Map<String, Object> readDictionary() throws IOException {
         int token = in.read();
         validateToken(token, Type.DICTIONARY);
 
-        Map<String, Object> map = new TreeMap<String, Object>();
+        Map<String, Object> map = new LinkedHashMap<String, Object>();
         while ((token = in.read()) != Bencode.TERMINATOR) {
             checkEOF(token);
 

src/main/java/com/dampcake/bencode/BencodeOutputStream.java

@@ -20,8 +20,6 @@
 import java.io.OutputStream;
 import java.nio.charset.Charset;
 import java.util.Map;
-import java.util.SortedMap;
-import java.util.TreeMap;
 
 /**
  * OutputStream for writing bencoded data.
@@ -157,14 +155,8 @@ private static String encode(final Iterable<?> l) {
         return buffer.toString();
     }
 
-    private static String encode(final Map<?, ?> m) {
-        if (m == null) throw new NullPointerException("m cannot be null");
-
-        Map<?, ?> map;
-        if (!(m instanceof SortedMap<?, ?>))
-            map = new TreeMap<Object, Object>(m);
-        else
-            map = m;
+    private static String encode(final Map<?, ?> map) {
+        if (map == null) throw new NullPointerException("map cannot be null");
 
         StringBuilder buffer = new StringBuilder();
         buffer.append(Bencode.DICTIONARY);

src/test/java/com/dampcake/bencode/BencodeOutputStreamTest.java

@@ -6,6 +6,8 @@
 import java.io.ByteArrayOutputStream;
 import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.LinkedHashMap;
+import java.util.TreeMap;
 import java.util.concurrent.ConcurrentSkipListMap;
 
 import static com.dampcake.bencode.Assert.assertThrows;
@@ -140,7 +142,7 @@ public void run() throws Exception {
     @Test
     @SuppressWarnings("unchecked")
     public void testWriteDictionary() throws Exception {
-        instance.writeDictionary(new HashMap<Object, Object>() {{
+        instance.writeDictionary(new LinkedHashMap<Object, Object>() {{
             put("string", "value");
             put("number", 123456);
             put("list", new ArrayList<Object>() {{
@@ -153,7 +155,7 @@ public void testWriteDictionary() throws Exception {
             }});
         }});
 
-        assertEquals("d4:dictd3:1234:test3:4565:thinge4:listl11:list-item-111:list-item-2e6:numberi123456e6:string5:valuee",
+        assertEquals("d6:string5:value6:numberi123456e4:listl11:list-item-111:list-item-2e4:dictd3:1234:test3:4565:thingee",
                 new String(out.toByteArray(), instance.getCharset()));
     }
 
@@ -168,7 +170,7 @@ public void testWriteDictionaryEmpty() throws Exception {
     public void testWriteDictionaryKeyCastException() throws Exception {
         assertThrows(ClassCastException.class, new Runnable() {
             public void run() throws Exception {
-                instance.writeDictionary(new HashMap<Object, Object>() {{
+                instance.writeDictionary(new TreeMap<Object, Object>() {{
                     put("string", "value");
                     put(123, "number-key");
                 }});

src/test/java/com/dampcake/bencode/BencodeTest.java

@@ -10,8 +10,10 @@
 import java.nio.charset.Charset;
 import java.util.ArrayList;
 import java.util.HashMap;
+import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.TreeMap;
 import java.util.concurrent.ConcurrentSkipListMap;
 
 import static org.hamcrest.core.IsInstanceOf.any;
@@ -354,7 +356,7 @@ public void testWriteListNull() throws Exception {
 
     @Test
     public void testWriteDictionary() throws Exception {
-        byte[] encoded = instance.encode(new HashMap<Object, Object>() {{
+        byte[] encoded = instance.encode(new LinkedHashMap<Object, Object>() {{
             put("string", "value");
             put("number", 123456);
             put("list", new ArrayList<Object>() {{
@@ -367,7 +369,7 @@ public void testWriteDictionary() throws Exception {
             }});
         }});
 
-        assertEquals("d4:dictd3:1234:test3:4565:thinge4:listl11:list-item-111:list-item-2e6:numberi123456e6:string5:valuee",
+        assertEquals("d6:string5:value6:numberi123456e4:listl11:list-item-111:list-item-2e4:dictd3:1234:test3:4565:thingee",
                 new String(encoded, instance.getCharset()));
     }
 
@@ -380,10 +382,9 @@ public void testWriteDictionaryEmpty() throws Exception {
 
     @Test
     public void testWriteDictionaryKeyCastException() throws Exception {
-        exception.expect(BencodeException.class);
-        exception.expectCause(any(ClassCastException.class));
+        exception.expect(any(ClassCastException.class));
 
-        instance.encode(new HashMap<Object, Object>() {{
+        instance.encode(new TreeMap<Object, Object>() {{
             put("string", "value");
             put(123, "number-key");
         }});