Wrapping a ByteBuffer with an InputStream

Question

I have a method that takes an InputStream and reads data from it. I would like to use this method with a ByteBuffer also. Is there a way to wrap a ByteBuffer so it can be ac

Answer 1

This is my version of InputStream & OutputStream implementation:

ByteBufferBackedInputStream:

public class ByteBufferBackedInputStream extends InputStream
{
  private ByteBuffer backendBuffer;

  public ByteBufferBackedInputStream(ByteBuffer backendBuffer) {
      Objects.requireNonNull(backendBuffer, "Given backend buffer can not be null!");
      this.backendBuffer = backendBuffer;
  }

  public void close() throws IOException {
      this.backendBuffer = null;
  }

  private void ensureStreamAvailable() throws IOException {
      if (this.backendBuffer == null) {
          throw new IOException("read on a closed InputStream!");
      }
  }

  @Override
  public int read() throws IOException {
      this.ensureStreamAvailable();
      return this.backendBuffer.hasRemaining() ? this.backendBuffer.get() & 0xFF : -1;
  }

  @Override
  public int read(@Nonnull byte[] buffer) throws IOException {
      return this.read(buffer, 0, buffer.length);
  }

  @Override
  public int read(@Nonnull byte[] buffer, int offset, int length) throws IOException {
      this.ensureStreamAvailable();
      Objects.requireNonNull(buffer, "Given buffer can not be null!");
      if (offset >= 0 && length >= 0 && length <= buffer.length - offset) {
          if (length == 0) {
              return 0;
          }
          else {
              int remainingSize = Math.min(this.backendBuffer.remaining(), length);
              if (remainingSize == 0) {
                  return -1;
              }
              else {
                  this.backendBuffer.get(buffer, offset, remainingSize);
                  return remainingSize;
              }
          }
      }
      else {
          throw new IndexOutOfBoundsException();
      }
  }

  public long skip(long n) throws IOException {
      this.ensureStreamAvailable();
      if (n <= 0L) {
          return 0L;
      }
      int length = (int) n;
      int remainingSize = Math.min(this.backendBuffer.remaining(), length);
      this.backendBuffer.position(this.backendBuffer.position() + remainingSize);
      return (long) length;
  }

  public int available() throws IOException {
      this.ensureStreamAvailable();
      return this.backendBuffer.remaining();
  }

  public synchronized void mark(int var1) {
  }

  public synchronized void reset() throws IOException {
      throw new IOException("mark/reset not supported");
  }

  public boolean markSupported() {
      return false;
  }
}

ByteBufferBackedOutputStream:

public class ByteBufferBackedOutputStream extends OutputStream
{
    private ByteBuffer backendBuffer;

    public ByteBufferBackedOutputStream(ByteBuffer backendBuffer) {
        Objects.requireNonNull(backendBuffer, "Given backend buffer can not be null!");
        this.backendBuffer = backendBuffer;
    }

    public void close() throws IOException {
        this.backendBuffer = null;
    }

    private void ensureStreamAvailable() throws IOException {
        if (this.backendBuffer == null) {
            throw new IOException("write on a closed OutputStream");
        }
    }

    @Override
    public void write(int b) throws IOException {
        this.ensureStreamAvailable();
        backendBuffer.put((byte) b);
    }

    @Override
    public void write(@Nonnull byte[] bytes) throws IOException {
        this.write(bytes, 0, bytes.length);
    }

    @Override
    public void write(@Nonnull byte[] bytes, int off, int len) throws IOException {
        this.ensureStreamAvailable();
        Objects.requireNonNull(bytes, "Given buffer can not be null!");
        if ((off < 0) || (off > bytes.length) || (len < 0) ||
            ((off + len) > bytes.length) || ((off + len) < 0))
        {
            throw new IndexOutOfBoundsException();
        }
        else if (len == 0) {
            return;
        }

        backendBuffer.put(bytes, off, len);
    }
}