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Java JDBC 4.2 (JRE 8+) driver for PostgreSQL database
There is a newer version: 42.7.3
/*
 * Copyright (c) 2011, PostgreSQL Global Development Group
 * See the LICENSE file in the project root for more information.
 */

package org.postgresql.util;

/**
 * Helper methods to parse java base types from byte arrays.
 *
 * @author Mikko Tiihonen
 */
public class ByteConverter {

  private ByteConverter() {
    // prevent instantiation of static helper class
  }

  /**
   * Parses a long value from the byte array.
   *
   * @param bytes The byte array to parse.
   * @param idx The starting index of the parse in the byte array.
   * @return parsed long value.
   */
  public static long int8(byte[] bytes, int idx) {
    return
        ((long) (bytes[idx + 0] & 255) << 56)
            + ((long) (bytes[idx + 1] & 255) << 48)
            + ((long) (bytes[idx + 2] & 255) << 40)
            + ((long) (bytes[idx + 3] & 255) << 32)
            + ((long) (bytes[idx + 4] & 255) << 24)
            + ((long) (bytes[idx + 5] & 255) << 16)
            + ((long) (bytes[idx + 6] & 255) << 8)
            + (bytes[idx + 7] & 255);
  }

  /**
   * Parses an int value from the byte array.
   *
   * @param bytes The byte array to parse.
   * @param idx The starting index of the parse in the byte array.
   * @return parsed int value.
   */
  public static int int4(byte[] bytes, int idx) {
    return
        ((bytes[idx] & 255) << 24)
            + ((bytes[idx + 1] & 255) << 16)
            + ((bytes[idx + 2] & 255) << 8)
            + ((bytes[idx + 3] & 255));
  }

  /**
   * Parses a short value from the byte array.
   *
   * @param bytes The byte array to parse.
   * @param idx The starting index of the parse in the byte array.
   * @return parsed short value.
   */
  public static short int2(byte[] bytes, int idx) {
    return (short) (((bytes[idx] & 255) << 8) + ((bytes[idx + 1] & 255)));
  }

  /**
   * Parses a boolean value from the byte array.
   *
   * @param bytes
   *          The byte array to parse.
   * @param idx
   *          The starting index to read from bytes.
   * @return parsed boolean value.
   */
  public static boolean bool(byte[] bytes, int idx) {
    return bytes[idx] == 1;
  }

  /**
   * Parses a float value from the byte array.
   *
   * @param bytes The byte array to parse.
   * @param idx The starting index of the parse in the byte array.
   * @return parsed float value.
   */
  public static float float4(byte[] bytes, int idx) {
    return Float.intBitsToFloat(int4(bytes, idx));
  }

  /**
   * Parses a double value from the byte array.
   *
   * @param bytes The byte array to parse.
   * @param idx The starting index of the parse in the byte array.
   * @return parsed double value.
   */
  public static double float8(byte[] bytes, int idx) {
    return Double.longBitsToDouble(int8(bytes, idx));
  }

  /**
   * Encodes a long value to the byte array.
   *
   * @param target The byte array to encode to.
   * @param idx The starting index in the byte array.
   * @param value The value to encode.
   */
  public static void int8(byte[] target, int idx, long value) {
    target[idx + 0] = (byte) (value >>> 56);
    target[idx + 1] = (byte) (value >>> 48);
    target[idx + 2] = (byte) (value >>> 40);
    target[idx + 3] = (byte) (value >>> 32);
    target[idx + 4] = (byte) (value >>> 24);
    target[idx + 5] = (byte) (value >>> 16);
    target[idx + 6] = (byte) (value >>> 8);
    target[idx + 7] = (byte) value;
  }

  /**
   * Encodes a int value to the byte array.
   *
   * @param target The byte array to encode to.
   * @param idx The starting index in the byte array.
   * @param value The value to encode.
   */
  public static void int4(byte[] target, int idx, int value) {
    target[idx + 0] = (byte) (value >>> 24);
    target[idx + 1] = (byte) (value >>> 16);
    target[idx + 2] = (byte) (value >>> 8);
    target[idx + 3] = (byte) value;
  }

  /**
   * Encodes a int value to the byte array.
   *
   * @param target The byte array to encode to.
   * @param idx The starting index in the byte array.
   * @param value The value to encode.
   */
  public static void int2(byte[] target, int idx, int value) {
    target[idx + 0] = (byte) (value >>> 8);
    target[idx + 1] = (byte) value;
  }

  /**
   * Encodes a boolean value to the byte array.
   *
   * @param target
   *          The byte array to encode to.
   * @param idx
   *          The starting index in the byte array.
   * @param value
   *          The value to encode.
   */
  public static void bool(byte[] target, int idx, boolean value) {
    target[idx] = value ? (byte) 1 : (byte) 0;
  }

  /**
   * Encodes a int value to the byte array.
   *
   * @param target The byte array to encode to.
   * @param idx The starting index in the byte array.
   * @param value The value to encode.
   */
  public static void float4(byte[] target, int idx, float value) {
    int4(target, idx, Float.floatToRawIntBits(value));
  }

  /**
   * Encodes a int value to the byte array.
   *
   * @param target The byte array to encode to.
   * @param idx The starting index in the byte array.
   * @param value The value to encode.
   */
  public static void float8(byte[] target, int idx, double value) {
    int8(target, idx, Double.doubleToRawLongBits(value));
  }
}