[GitHub] [beam] pabloem commented on a diff in pull request #15549: [BEAM-11997] Changed RedisIO implementation to SDF

[GitBox <gi...@apache.org>]

pabloem commented on code in PR #15549:
URL: https://github.com/apache/beam/pull/15549#discussion_r847813348


##########
sdks/java/io/redis/src/main/java/org/apache/beam/sdk/io/redis/RedisCursor.java:
##########
@@ -0,0 +1,149 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.beam.sdk.io.redis;
+
+import static org.apache.beam.vendor.guava.v26_0_jre.com.google.common.base.Preconditions.checkNotNull;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.Serializable;
+import java.nio.ByteBuffer;
+import java.util.Objects;
+import javax.annotation.Nonnull;
+import org.apache.beam.sdk.coders.BigEndianLongCoder;
+import org.apache.beam.sdk.io.range.ByteKey;
+import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.annotations.VisibleForTesting;
+import org.checkerframework.checker.nullness.qual.Nullable;
+
+public class RedisCursor implements Comparable<RedisCursor>, Serializable {
+
+  public static final RedisCursor ZERO_CURSOR = RedisCursor.of("0", 8);
+
+  private final String cursor;
+  private final ByteKey byteCursor;
+  private final long dbSize;
+  private final int nBits;
+
+  public static RedisCursor of(String cursor, long dbSize) {
+    return new RedisCursor(cursor, dbSize);
+  }
+
+  public static RedisCursor of(ByteKey byteCursor, long dbSize) {
+    return new RedisCursor(byteCursor, dbSize);
+  }
+
+  private RedisCursor(ByteKey byteCursor, long dbSize) {
+    this.byteCursor = byteCursor;
+    this.dbSize = dbSize;
+    this.nBits = getTablePow(dbSize);
+    this.cursor = byteKeyToString(byteCursor, nBits);
+  }
+
+  private RedisCursor(String cursor, long dbSize) {
+    this.cursor = cursor;
+    this.dbSize = dbSize;
+    this.nBits = getTablePow(dbSize);
+    this.byteCursor = stringCursorToByteKey(cursor, this.nBits);
+  }
+
+  /**
+   * {@link RedisCursor} implements {@link Comparable Comparable&lt;RedisCursor&gt;} by transforming
+   * the cursors to an index of the Redis table.
+   */
+  @Override
+  public int compareTo(@Nonnull RedisCursor other) {
+    checkNotNull(other, "other");
+    return Long.compare(Long.parseLong(cursor), Long.parseLong(other.cursor));
+  }
+
+  @Override
+  public boolean equals(@Nullable Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    RedisCursor that = (RedisCursor) o;
+    return dbSize == that.dbSize
+        && nBits == that.nBits
+        && Objects.equals(cursor, that.cursor)
+        && Objects.equals(byteCursor, that.byteCursor);
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(cursor, byteCursor, dbSize, nBits);
+  }
+
+  public String getCursor() {
+    return cursor;
+  }
+
+  public ByteKey getByteCursor() {
+    return byteCursor;
+  }
+
+  public long getDbSize() {
+    return dbSize;
+  }
+
+  @VisibleForTesting
+  static ByteKey stringCursorToByteKey(String cursor, int nBits) {
+    long cursorLong = Long.parseLong(cursor);
+    long reversed = shiftBits(cursorLong, nBits);
+    BigEndianLongCoder coder = BigEndianLongCoder.of();
+    ByteArrayOutputStream os = new ByteArrayOutputStream();
+    try {
+      coder.encode(reversed, os);
+    } catch (IOException e) {
+      throw new IllegalArgumentException("invalid redis cursor " + cursor);
+    }
+    byte[] byteArray = os.toByteArray();
+    return ByteKey.copyFrom(byteArray);
+  }
+
+  @VisibleForTesting
+  static long shiftBits(long a, int nBits) {
+    long b = 0;

Review Comment:
   can you please use Long.reverse? 



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