Minor improvements

Author: filip26

README.md

@@ -109,20 +109,12 @@ if (MultihashCodec.SHA2_384.isEncoded(encoded)) {
   ...
 }
 
-
-/* get registry initialized with all multihash codecs */
-var registry = MulticodecRegistry.getInstance(Tag.Multihash);
-
 /* determine digest index  */
-var index = registry.getCodec(encoded)
+var index = decoder.getCodec(encoded)
                     .map(Multihash.class::cast)
-                    .mapToInt(codec -> codec.length() + codec.digestLength(encoded))
+                    .mapToInt(codec -> encoded.length - codec.digestLength(encoded))
                     .orElseThrow(() -> new IllegalArgumentException("Unsupported multihash."));
 
-/* encode an input as multihash */
-byte[] encoded = registry.getCodec(code)
-                         .map(codec -> codec.encode(input))
-                         .orElseThrow(() -> new IllegalArgumentException("Unsupported multihash."));
 ```
 
 ## Installation

src/test/java/com/apicatalog/multihash/MultihashTest.java

@@ -14,6 +14,7 @@
 import com.apicatalog.multicodec.Multicodec.Tag;
 import com.apicatalog.multicodec.MulticodecDecoder;
 import com.apicatalog.multicodec.codec.MultihashCodec;
+import com.apicatalog.uvarint.UVarInt;
 
 class MultihashTest {
 
@@ -66,6 +67,8 @@ void testDecodeFromIndex(byte[] input, Multihash codec, byte[] expected) {
 
         System.arraycopy(input, 0, array, index, input.length);
         assertArrayEquals(expected, codec.decode(array, index));
+        assertEquals(expected.length, codec.digestLength(array, index));
+        assertEquals(codec.length() + UVarInt.byteLength(expected.length), input.length - codec.digestLength(array, index));
     }
 
     @ParameterizedTest(name = "{index}")
@@ -80,6 +83,8 @@ void testDecodeRange(byte[] input, Multihash codec, byte[] expected) {
 
         System.arraycopy(input, 0, array, index, input.length);
         assertArrayEquals(expected, codec.decode(array, index, input.length));
+        assertEquals(expected.length, codec.digestLength(array, index));
+        assertEquals(codec.length() + UVarInt.byteLength(expected.length), input.length - codec.digestLength(array, index));        
     }
 
     @ParameterizedTest(name = "{index}")