ma.vi.base.io.SpyInputStream Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of com.vikmad.base Show documentation
Base algos, data structures and utilities
The newest version!
/*
 * Copyright (c) 2018 Vikash Madhow
 */

package ma.vi.base.io;

import java.io.FilterInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

/**
 * An input stream that can be used to "spy" on another input stream. It works by intercepting all reads on the spied
 * input stream and sending the read data to a target output stream such as System.out.
 *
 * @author [email protected]
 */
public class SpyInputStream extends FilterInputStream {
  /**
   * Construct a SpyInputStream wrapping the provided java.io.InputStream and sending intercepted reads to the specified
   * output stream.
   *
   * @param in     java.io.InputStream to wrap
   * @param target Target output stream for intercepted reads
   * @throws IOException If in or target is null
   */
  public SpyInputStream(InputStream in, OutputStream target) throws IOException {
    super(in);
    if (target == null) {
      throw new IOException("Target output stream must not be null");
    }
    this.target = target;
  }

  /**
   * Reads a byte.
   *
   * @return The byte read or -1 if end-of-input reached
   * @throws IOException If an error occurs during input
   */
  @Override
  public int read() throws IOException {
    int b = super.read();
    target.write(b);
    return b;
  }

  /**
   * Reads some bytes into the byte array.
   *
   * @param b byte array where read bytes will be copied
   * @return The number of bytes read
   * @throws IOException If an error occurs during input
   */
  @Override
  public int read(byte[] b) throws IOException {
    int count = super.read(b);
    target.write(b, 0, count);
    return count;
  }

  /**
   * Reads some bytes into the byte array.
   *
   * @param b      byte array where the read bytes will be copied
   * @param offset Read bytes will be copied into the byte array starting at this position
   * @param length Maximum number of bytes to read
   * @return The number of bytes actually read. May be less than length.
   * @throws IOException If an error occurs during input
   */
  @Override
  public int read(byte[] b, int offset, int length) throws IOException {
    int count = super.read(b, offset, length);
    target.write(b, offset, count);
    return count;
  }

  /**
   * Closes this stream.
   *
   * @throws IOException If an I/O error occurs
   */
  @Override
  public void close() throws IOException {
    super.close();
    target.close();
  }

  /**
   * Target output stream to send spied bytes to.
   */
  private OutputStream target;
}