spark-gpu-master/unsafe/src/main/java/org/apache/spark/unsafe/types/ByteArray.java
/*
 * 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.spark.unsafe.types;

import org.apache.spark.unsafe.Platform;

import java.util.Arrays;

public final class ByteArray {

  public static final byte[] EMPTY_BYTE = new byte[0];

  /**
   * Writes the content of a byte array into a memory address, identified by an object and an
   * offset. The target memory address must already been allocated, and have enough space to
   * hold all the bytes in this string.
   */
  public static void writeToMemory(byte[] src, Object target, long targetOffset) {
    Platform.copyMemory(src, Platform.BYTE_ARRAY_OFFSET, target, targetOffset, src.length);
  }

  /**
   * Returns a 64-bit integer that can be used as the prefix used in sorting.
   */
  public static long getPrefix(byte[] bytes) {
    if (bytes == null) {
      return 0L;
    } else {
      final int minLen = Math.min(bytes.length, 8);
      long p = 0;
      for (int i = 0; i < minLen; ++i) {
        p |= (128L + Platform.getByte(bytes, Platform.BYTE_ARRAY_OFFSET + i))
            << (56 - 8 * i);
      }
      return p;
    }
  }

  public static byte[] subStringSQL(byte[] bytes, int pos, int len) {
    // This pos calculation is according to UTF8String#subStringSQL
    if (pos > bytes.length) {
      return EMPTY_BYTE;
    }
    int start = 0;
    int end;
    if (pos > 0) {
      start = pos - 1;
    } else if (pos < 0) {
      start = bytes.length + pos;
    }
    if ((bytes.length - start) < len) {
      end = bytes.length;
    } else {
      end = start + len;
    }
    start = Math.max(start, 0); // underflow
    if (start >= end) {
      return EMPTY_BYTE;
    }
    return Arrays.copyOfRange(bytes, start, end);
  }
}
