large dataset

src/main/java/difflib/DiffUtils.java

@@ -26,6 +26,7 @@ import difflib.patch.Delta;
 import difflib.patch.Equalizer;
 import difflib.patch.Patch;
 import difflib.patch.PatchFailedException;
+import java.util.Arrays;
 import java.util.Collections;
 import java.util.LinkedList;
 import java.util.List;
@@ -52,6 +53,13 @@ public final class DiffUtils {
     public static <T> Patch<T> diff(List<T> original, List<T> revised) throws DiffException {
         return DiffUtils.diff(original, revised, new MyersDiff<>());
     }
+    
+    /**
+     * Computes the difference between the original and revised text.
+     */
+    public static Patch<String> diff(String originalText, String revisedText) throws DiffException {
+        return DiffUtils.diff(Arrays.asList(originalText.split("\n")), Arrays.asList(revisedText.split("\n")));
+    }
 
     /**
      * Computes the difference between the original and revised list of elements with default diff

src/main/java/difflib/patch/Patch.java

@@ -85,4 +85,9 @@ public final class Patch<T> {
         Collections.sort(deltas, comparing(d -> d.getOriginal().getPosition()));
         return deltas;
     }
+
+    @Override
+    public String toString() {
+        return "Patch{" + "deltas=" + deltas + '}';
+    }
 }

src/test/java/difflib/DiffUtilsTest.java

@@ -7,13 +7,22 @@ import difflib.patch.DeleteDelta;
 import difflib.patch.Delta;
 import difflib.patch.InsertDelta;
 import difflib.patch.Patch;
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStream;
+import java.io.InputStreamReader;
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
 import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.List;
+import static java.util.stream.Collectors.toList;
+import java.util.zip.ZipFile;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertTrue;
+import org.junit.Ignore;
 import org.junit.Test;
 
 public class DiffUtilsTest {
@@ -101,13 +110,46 @@ public class DiffUtilsTest {
         List<Integer> revised = Arrays.asList(2, 3, 4, 6);
 
         final Patch<Integer> patch = DiffUtils.diff(original, revised);
-        
+
         for (Delta delta : patch.getDeltas()) {
             System.out.println(delta);
         }
-        
+
         assertEquals(2, patch.getDeltas().size());
         assertEquals("[DeleteDelta, position: 0, lines: [1]]", patch.getDeltas().get(0).toString());
         assertEquals("[ChangeDelta, position: 4, lines: [5] to [6]]", patch.getDeltas().get(1).toString());
     }
+
+    @Test
+    public void testDiffMissesChangeForkDnaumenkoIssue31() throws DiffException {
+        List<String> original = Arrays.asList("line1", "line2", "line3");
+        List<String> revised = Arrays.asList("line1", "line2-2", "line4");
+
+        Patch<String> patch = DiffUtils.diff(original, revised);
+        assertEquals(1, patch.getDeltas().size());
+        assertEquals("[ChangeDelta, position: 1, lines: [line2, line3] to [line2-2, line4]]", patch.getDeltas().get(0).toString());
+    }
+
+    /**
+     * To test this, the greedy meyer algorithm is not suitable.
+     */
+    @Test
+    @Ignore
+    public void testPossibleDiffHangOnLargeDatasetDnaumenkoIssue26() throws IOException, DiffException {
+        ZipFile zip = new ZipFile(TestConstants.MOCK_FOLDER + "/large_dataset1.zip");
+        
+        Patch<String> patch = DiffUtils.diff(
+                readStringListFromInputStream(zip.getInputStream(zip.getEntry("ta"))), 
+                readStringListFromInputStream(zip.getInputStream(zip.getEntry("tb"))));
+        
+        assertEquals(1, patch.getDeltas().size());
+    }
+    
+    private static List<String> readStringListFromInputStream(InputStream is) throws IOException {
+        try (BufferedReader reader = new BufferedReader(
+                new InputStreamReader(is, Charset.forName(StandardCharsets.UTF_8.name())))) {
+            
+            return reader.lines().collect(toList());
+        }
+    }
 }