Add PooledBinary Class (#308)

java/common/src/main/java/org/apache/tsfile/utils/PooledBinary.java

@@ -0,0 +1,175 @@
+/*
+ * 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.tsfile.utils;
+
+import java.io.Serializable;
+import java.nio.charset.Charset;
+import java.nio.charset.StandardCharsets;
+
+import static org.apache.tsfile.utils.RamUsageEstimator.shallowSizeOfInstance;
+
+/**
+ * This class represents a pooled binary object for application layer. It is designed to improve
+ * allocation performance and reduce GC overhead by reusing binary objects from a pool instead of
+ * creating new instances each time. WARNING: The actual length of the binary may not equal to the
+ * length of the underlying byte array. Always use getLength() instead of getValue().length to get
+ * the correct length.
+ */
+public class PooledBinary implements Comparable<PooledBinary>, Serializable, Accountable {
+
+  private static final long INSTANCE_SIZE = shallowSizeOfInstance(PooledBinary.class);
+  private static final long serialVersionUID = 6394197743397020735L;
+  public static final PooledBinary EMPTY_VALUE = new PooledBinary(new byte[0]);
+
+  private Binary binary;
+
+  private int length;
+
+  private int arenaIndex = -1;
+
+  /** if the bytes v is modified, the modification is visible to this binary. */
+  public PooledBinary(byte[] v) {
+    this.binary = new Binary(v);
+    this.length = binary.getLength();
+  }
+
+  public PooledBinary(String s, Charset charset) {
+    this.binary = new Binary(s, charset);
+    this.length = binary.getLength();
+  }
+
+  public PooledBinary(byte[] v, int length, int arenaIndex) {
+    this.binary = new Binary(v);
+    this.length = length;
+    this.arenaIndex = arenaIndex;
+  }
+
+  @Override
+  public int compareTo(PooledBinary other) {
+    if (other == null) {
+      if (this.binary.getValues() == null) {
+        return 0;
+      } else {
+        return 1;
+      }
+    }
+
+    // copied from StringLatin1.compareT0
+    int len1 = getLength();
+    int len2 = other.getLength();
+    int lim = Math.min(len1, len2);
+    byte[] v0 = this.binary.getValues();
+    byte[] v1 = other.binary.getValues();
+    for (int k = 0; k < lim; k++) {
+      if (v0[k] != v1[k]) {
+        return getChar(v0, k) - getChar(v1, k);
+      }
+    }
+    return len1 - len2;
+  }
+
+  // avoid overflow
+  private char getChar(byte[] val, int index) {
+    return (char) (val[index] & 0xff);
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (o == null || getClass() != o.getClass()) {
+      return false;
+    }
+    PooledBinary otherBinary = (PooledBinary) o;
+
+    if (length != otherBinary.length) {
+      return false;
+    }
+
+    byte[] v0 = binary.getValues();
+    byte[] v1 = otherBinary.binary.getValues();
+
+    for (int i = 0; i < length; i++) {
+      if (v0[i] != v1[i]) {
+        return false;
+      }
+    }
+
+    return true;
+  }
+
+  @Override
+  public int hashCode() {
+    // copied from Arrays.hashCode
+    if (binary.getValues() == null) return 0;
+
+    int result = 1;
+    byte[] val = binary.getValues();
+    for (int i = 0; i < length; i++) result = 31 * result + val[i];
+
+    return result;
+  }
+
+  /**
+   * get length.
+   *
+   * @return length
+   */
+  public int getLength() {
+    return this.length;
+  }
+
+  public String getStringValue(Charset charset) {
+    return new String(this.binary.getValues(), 0, length, charset);
+  }
+
+  @Override
+  public String toString() {
+    // use UTF_8 by default since toString do not provide parameter
+    return getStringValue(StandardCharsets.UTF_8);
+  }
+
+  public byte[] getValues() {
+    return binary.getValues();
+  }
+
+  public void setValues(byte[] values) {
+    this.binary.setValues(values);
+    this.length = this.binary.getLength();
+  }
+
+  public void setValues(byte[] values, int length) {
+    this.binary.setValues(values);
+    this.length = length;
+  }
+
+  public int getArenaIndex() {
+    return this.arenaIndex;
+  }
+
+  @Override
+  public long ramBytesUsed() {
+    return INSTANCE_SIZE + binary.ramBytesUsed();
+  }
+
+  public Binary toBinary() {
+    return binary;
+  }
+}