only update processed parts count with unique parts

src/main/java/com/sparrowwallet/hummingbird/fountain/FountainDecoder.java

@@ -16,6 +16,7 @@ import static com.sparrowwallet.hummingbird.fountain.FountainUtils.chooseFragmen
 public class FountainDecoder {
     private final Set<Integer> recievedPartIndexes = new TreeSet<>();
     private Set<Integer> lastPartIndexes;
+    private final Set<Integer> processedPartHashes = new HashSet<>();
     private int processedPartsCount = 0;
     private Result result;
     private long checksum;
@@ -114,8 +115,10 @@ public class FountainDecoder {
             processQueueItem();
         }
 
-        // Keep track of how many parts we've processed
-        processedPartsCount += 1;
+        // Keep track of how many unique parts we've processed
+        if(processedPartHashes.add(encoderPart.hashCode())) {
+            processedPartsCount++;
+        }
         //printPartEnd();
 
         return true;

src/main/java/com/sparrowwallet/hummingbird/fountain/FountainEncoder.java

@@ -181,5 +181,41 @@ public class FountainEncoder {
 
             return new Part(seqNum.getValue().longValue(), seqLen.getValue().intValue(), messageLen.getValue().intValue(), checksum.getValue().longValue(), data.getBytes());
         }
+
+        @Override
+        public boolean equals(Object o) {
+            if(this == o) {
+                return true;
+            }
+            if(o == null || getClass() != o.getClass()) {
+                return false;
+            }
+
+            Part part = (Part) o;
+
+            if(seqNum != part.seqNum) {
+                return false;
+            }
+            if(seqLen != part.seqLen) {
+                return false;
+            }
+            if(messageLen != part.messageLen) {
+                return false;
+            }
+            if(checksum != part.checksum) {
+                return false;
+            }
+            return Arrays.equals(data, part.data);
+        }
+
+        @Override
+        public int hashCode() {
+            int result = (int) (seqNum ^ (seqNum >>> 32));
+            result = 31 * result + seqLen;
+            result = 31 * result + messageLen;
+            result = 31 * result + (int) (checksum ^ (checksum >>> 32));
+            result = 31 * result + Arrays.hashCode(data);
+            return result;
+        }
     }
 }

src/test/java/com/sparrowwallet/hummingbird/URTest.java

@@ -216,4 +216,26 @@ public class URTest {
         Assert.assertEquals(TestUtils.bytesToHex(ur.toBytes()), "70736274ff0100520200000001adb4134883273f90371c364743e1816de7099df3895dbc95ebcd19beb83200ec0000000000ffffffff01e80300000000000016001457766b7686ca60e5221119966bdfe1d1f4b62181000000000001011f581b0000000000001600145da1bc9a730b7e9d209f15aff9c096f6bbd89d26220603ccd4532b1350e04cbaff91056bdb08bd3877b4fcb8cd70aaeda5239ce112547b180000000054000080000000800000008000000000060000000000");
         Arrays.stream(fragments).forEach(part -> Assert.assertTrue(LegacyURDecoder.isLegacyURFragment(part)));
     }
+
+    @Test
+    public void testDuplicateDecode() {
+        String[] parts = new String[] {
+                "ur:bytes/1-9/lpadascfadaxcywenbpljkhdcahkadaemejtswhhylkepmykhhtsytsnoyoyaxaedsuttydmmhhpktpmsrjtdkgslpgh",
+                "ur:bytes/2-9/lpaoascfadaxcywenbpljkhdcagwdpfnsboxgwlbaawzuefywkdplrsrjynbvygabwjldapfcsgmghhkhstlrdcxaefz",
+                "ur:bytes/3-9/lpaxascfadaxcywenbpljkhdcahelbknlkuejnbadmssfhfrdpsbiegecpasvssovlgeykssjykklronvsjksopdzmol"
+        };
+
+        URDecoder urDecoder = new URDecoder();
+        Assert.assertEquals(0, urDecoder.getProcessedPartsCount());
+        urDecoder.receivePart(parts[0]);
+        Assert.assertEquals(1, urDecoder.getProcessedPartsCount());
+        urDecoder.receivePart(parts[0]);
+        Assert.assertEquals(1, urDecoder.getProcessedPartsCount());
+        urDecoder.receivePart(parts[1]);
+        Assert.assertEquals(2, urDecoder.getProcessedPartsCount());
+        urDecoder.receivePart(parts[0]);
+        Assert.assertEquals(2, urDecoder.getProcessedPartsCount());
+        urDecoder.receivePart(parts[2]);
+        Assert.assertEquals(3, urDecoder.getProcessedPartsCount());
+    }
 }