Zero excessive bits in readBooleanList

Author: shirolimit

src/main/java/com/github/shyiko/mysql/binlog/event/deserialization/TableMapEventMetadataDeserializer.java

@@ -252,8 +252,8 @@ public TableMapEventMetadata deserialize(BinaryLogEventDataReader eventDataReade
         return result;
     }
 
-
-    private static BitSet readBooleanList(ByteArrayInputStream inputStream, int length) throws IOException {
+    // The method is visible for testing purposes.
+    public static BitSet readBooleanList(ByteArrayInputStream inputStream, int length) throws IOException {
         BitSet result = new BitSet();
         // according to MySQL internals the amount of storage required for N columns is INT((N+7)/8) bytes
         byte[] bytes = inputStream.read((length + 7) >> 3);
@@ -265,7 +265,8 @@ private static BitSet readBooleanList(ByteArrayInputStream inputStream, int leng
         return result;
     }
 
-    private static BitSet readBooleanList(BinaryLogEventDataReader eventDataReader, int length) {
+    // The method is visible for testing purposes.
+    public static BitSet readBooleanList(BinaryLogEventDataReader eventDataReader, int length) {
         byte[] bytes = eventDataReader.readBytes((length + 7) >> 3);
 
         // Bit reversion is taken from Hacker's Delight 2nd Edition 7-1.
@@ -276,6 +277,8 @@ private static BitSet readBooleanList(BinaryLogEventDataReader eventDataReader,
             b = (byte)(((b & 0x0f) << 4) | ((b >>> 4) & 0x0f));
             bytes[i] = b;
         }
+        byte mask = (byte)(0xff >> (bytes.length * 8 - length));
+        bytes[bytes.length - 1] = (byte)(bytes[bytes.length - 1] & mask);
 
         return BitSet.valueOf(bytes);
     }

src/test/java/com/github/shyiko/mysql/binlog/event/deserialization/TableMapEventMetadataDeserializerTest.java

@@ -5,12 +5,14 @@
 import org.junit.Test;
 
 import java.io.IOException;
+import java.nio.ByteBuffer;
 import java.util.BitSet;
 import java.util.stream.IntStream;
-import java.util.stream.Stream;
 
 import org.junit.Assert;
 
+import static junit.framework.Assert.assertEquals;
+
 public class TableMapEventMetadataDeserializerTest {
     private static final byte[] DATA = {
         (byte)0x86, 0x00, 0x00, 0x00, 0x00, 0x00, 0x01, 0x00, 0x05, 0x74, 0x70, 0x63, 0x63, 0x32, 0x00, 0x09,
@@ -38,6 +40,48 @@ public void deserialize_shouldProperlyDeserializeData_withBinaryReader() throws
         assertEventData(actual);
     }
 
+    @Test
+    public void readBooleanList_shouldConsistentlyDeserializeBitSet() throws IOException{
+        ReadBooleanListTestData[] testData = {
+            // 01100101 -> 01100xxx -> {1, 2}
+            new ReadBooleanListTestData(new byte[]{0x65}, 5, new int[]{1, 2}),
+            // 01100101 -> 01100101 -> {1, 2, 5, 7}
+            new ReadBooleanListTestData(new byte[]{0x65}, 8, new int[]{1, 2, 5, 7}),
+            // 01011101 00010001 -> 01011101 000xxxxx -> {1, 3, 4, 5, 7}
+            new ReadBooleanListTestData(new byte[]{0x5d, 0x11}, 11, new int[]{1, 3, 4, 5, 7}),
+            // 01001000 11111111 -> 01001000 1111111x -> {1, 4, 8, 9, 10, 11, 12, 13, 14}
+            new ReadBooleanListTestData(new byte[]{0x48, (byte)0xff}, 15, new int[]{1, 4, 8, 9, 10, 11, 12, 13, 14}),
+            // 01010101 01101100 01000011 -> 10111010 10001000 0100001x -> {1, 3, 5, 7, 9, 10, 12, 13, 17, 22}
+            new ReadBooleanListTestData(new byte[]{0x55, 0x6c, 0x43}, 23, new int[]{1, 3, 5, 7, 9, 10, 12, 13, 17, 22}),
+        };
+
+        for (int i = 0; i < testData.length; i++) {
+            ReadBooleanListTestData currentTest = testData[i];
+            BinaryLogEventDataReader reader = new BinaryLogEventDataReader(ByteBuffer.wrap(currentTest.data));
+            ByteArrayInputStream inputStream = new ByteArrayInputStream(currentTest.data);
+
+            BitSet readerBitSet = TableMapEventMetadataDeserializer.readBooleanList(reader, currentTest.length);
+            BitSet streamBitSet = TableMapEventMetadataDeserializer.readBooleanList(inputStream, currentTest.length);
+
+            BitSet expectedBitSet = IntStream.of(currentTest.expectedBitsSet).collect(BitSet::new, BitSet::set, BitSet::or);
+
+            assertEquals(String.format("Unexpected bits set in case %d", i), expectedBitSet, readerBitSet);
+            assertEquals(String.format("Reader and stream results don't match in case %d", i), streamBitSet, readerBitSet);
+        }
+    }
+
+    public static class ReadBooleanListTestData {
+        public final byte[] data;
+        public final int length;
+        public final int[] expectedBitsSet;
+
+        public ReadBooleanListTestData(byte[] data, int length, int[] expectedBitsSet) {
+            this.data = data;
+            this.length = length;
+            this.expectedBitsSet = expectedBitsSet;
+        }
+    }
+
     private static void assertEventData(TableMapEventData actual) {
         Assert.assertEquals(134L, actual.getTableId());
         Assert.assertEquals("tpcc2", actual.getDatabase());