content: /*
   * 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
   *
   *     https://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.avro.util;
  
  import java.io.Externalizable;
  import java.io.IOException;
  import java.io.ObjectInput;
  import java.io.ObjectOutput;
  import java.nio.charset.StandardCharsets;
  import java.util.Arrays;
  
  import org.apache.avro.SystemLimitException;
  
  /**
   * A Utf8 string. Unlike {@link String}, instances are mutable. This is more
   * efficient than {@link String} when reading or writing a sequence of values,
   * as a single instance may be reused.
   */
  public class Utf8 implements Comparable<Utf8>, CharSequence, Externalizable {
  
    private static final byte[] EMPTY = new byte[0];
  
    private byte[] bytes;
    private int hash;
    private int length;
    private String string;
  
    public Utf8() {
      this.bytes = EMPTY;
      this.hash = 1;
    }
  
    public Utf8(String string) {
      byte[] bytes = getBytesFor(string);
      int length = bytes.length;
      SystemLimitException.checkMaxStringLength(length);
      this.bytes = bytes;
      this.length = length;
      this.string = string;
    }
  
    public Utf8(Utf8 other) {
      this.length = other.length;
      this.bytes = Arrays.copyOf(other.bytes, other.length);
      this.string = other.string;
      this.hash = other.hash;
    }
  
    public Utf8(byte[] bytes) {
      int length = bytes.length;
      SystemLimitException.checkMaxStringLength(length);
      this.bytes = bytes;
      this.length = length;
    }
  
    Utf8(String string, int length) {
      this(string);
      this.length = length;
    }
  
    /**
     * Return UTF-8 encoded bytes. Only valid through {@link #getByteLength()}
     * assuming the bytes have been fully copied into the underlying buffer from the
     * source.
     *
     * @see #setByteLength(int)
     * @return a reference to the underlying byte array
     */
    public byte[] getBytes() {
      return bytes;
    }
  
    /** Return length in bytes. */
    public int getByteLength() {
      return length;
    }
  
    /**
     * Set length in bytes. When calling this method, even if the new length is the
     * same as the current length, the cached contents of this Utf8 object will be
     * wiped out. After calling this method, no assumptions should be made about the
     * internal state (e.g., contents, hashcode, equality, etc.) of this Utf8 String
     * other than the internal buffer being large enough to accommodate a String of
     * the new length. This should be called immediately before reading a String
     * from the underlying data source.
     *
     * @param newLength the new length of the underlying buffer
     * @return a reference to this object.
     * @see org.apache.avro.io.BinaryDecoder#readString(Utf8)
     */
    public Utf8 setByteLength(int newLength) {
      SystemLimitException.checkMaxStringLength(newLength);
  
      // Note that if the buffer size increases, the internal buffer is zero-ed out.
      // If the buffer is large enough, just the length pointer moves and the old
      // contents remain. For consistency's sake, we could zero-out the buffer in
      // both cases, but would be a perf hit.
      if (this.bytes.length < newLength) {
        this.bytes = new byte[newLength];
      }
      this.length = newLength;
      this.string = null;
      this.hash = 0;
      return this;
    }
  
    /** Set to the contents of a String. */
    public Utf8 set(String string) {
      byte[] bytes = getBytesFor(string);
      int length = bytes.length;
      SystemLimitException.checkMaxStringLength(length);
      this.bytes = bytes;
      this.length = length;
      this.string = string;
      this.hash = 0;
      return this;
    }
  
    public Utf8 set(Utf8 other) {
      if (this.bytes.length < other.length) {
        this.bytes = new byte[other.length];
      }
      this.length = other.length;
      System.arraycopy(other.bytes, 0, bytes, 0, length);
      this.string = other.string;
      this.hash = other.hash;
      return this;
    }
  
    @Override
    public String toString() {
      if (this.length == 0)
        return "";
      if (this.string == null) {
        this.string = new String(bytes, 0, length, StandardCharsets.UTF_8);
      }
      return this.string;
    }
  
    @Override
    public boolean equals(Object o) {
      if (o == this)
        return true;
      if (!(o instanceof Utf8))
        return false;
      Utf8 that = (Utf8) o;
      if (!(this.length == that.length))
        return false;
      // For longer strings, leverage vectorization (JDK 9+) to determine equality
      // For shorter strings, the overhead of this method defeats the value
      if (this.length > 7)
        return Arrays.equals(this.bytes, 0, this.length, that.bytes, 0, that.length);
      byte[] thatBytes = that.bytes;
      for (int i = 0; i < this.length; i++)
        if (bytes[i] != thatBytes[i])
          return false;
      return true;
    }
  
    @Override
    public int hashCode() {
      int h = hash;
      if (h == 0) {
        byte[] bytes = this.bytes;
        int length = this.length;
        // If the array is filled, use the underlying JDK hash functionality.
        // Starting with JDK 21, the underlying implementation is vectorized.
        if (length > 7 && bytes.length == length) {
          h = Arrays.hashCode(bytes);
        } else {
          h = 1;
          for (int i = 0; i < length; i++) {
            h = h * 31 + bytes[i];
          }
        }
        this.hash = h;
      }
      return h;
    }
  
    @Override
    public int compareTo(Utf8 that) {
      return Arrays.compare(this.bytes, 0, this.length, that.bytes, 0, that.length);
    }
  
    // CharSequence implementation
    @Override
    public char charAt(int index) {
      return toString().charAt(index);
    }
  
    @Override
    public int length() {
      return toString().length();
    }
  
    @Override
    public CharSequence subSequence(int start, int end) {
      return toString().subSequence(start, end);
    }
  
    /** Gets the UTF-8 bytes for a String */
    public static byte[] getBytesFor(String str) {
      return str.getBytes(StandardCharsets.UTF_8);
    }
  
    @Override
    public void writeExternal(ObjectOutput out) throws IOException {
      out.writeInt(bytes.length);
      out.write(bytes);
    }
  
    @Override
    public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
      setByteLength(in.readInt());
      in.readFully(bytes);
    }
  
    public static int compareSequences(CharSequence cs1, CharSequence cs2) {
      if (cs1 == cs2) {
        return 0;
      }
  
      if (cs1 == null || cs2 == null) {
        return cs1 == null ? 1 : -1;
      }
  
      if (cs1.getClass() == cs2.getClass() && cs1 instanceof Comparable) {
        return ((Comparable<Object>) cs1).compareTo(cs2);
      }
  
      for (int i = 0, len = Math.min(cs1.length(), cs2.length()); i < len; i++) {
        char a = cs1.charAt(i);
        char b = cs2.charAt(i);
        if (a != b) {
          return a - b;
        }
      }
  
      return cs1.length() - cs2.length();
    }
  }
  