content: /*
   * Copyright (c) 2020, Oracle and/or its affiliates.
   *
   * This program is free software; you can redistribute it and/or modify it under
   * the terms of the GNU General Public License, version 2.0, as published by the
   * Free Software Foundation.
   *
   * This program is also distributed with certain software (including but not
   * limited to OpenSSL) that is licensed under separate terms, as designated in a
   * particular file or component or in included license documentation. The
   * authors of MySQL hereby grant you an additional permission to link the
   * program and your derivative works with the separately licensed software that
   * they have included with MySQL.
   *
   * Without limiting anything contained in the foregoing, this file, which is
   * part of MySQL Connector/J, is also subject to the Universal FOSS Exception,
   * version 1.0, a copy of which can be found at
   * http://oss.oracle.com/licenses/universal-foss-exception.
   *
   * This program is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
   * FOR A PARTICULAR PURPOSE. See the GNU General Public License, version 2.0,
   * for more details.
   *
   * You should have received a copy of the GNU General Public License along with
   * this program; if not, write to the Free Software Foundation, Inc.,
   * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301  USA
   */
  
  package com.mysql.cj.protocol.x;
  
  import java.io.FilterInputStream;
  import java.io.IOException;
  import java.io.InputStream;
  
  /**
   * An {@link InputStream} wrapper that limits the number of bytes that can be read form the underlying {@link InputStream}.
   */
  public class ConfinedInputStream extends FilterInputStream {
      private int limit = 0;
      private int consumed = 0;
  
      private boolean closed = false;
  
      protected ConfinedInputStream(InputStream in) {
          this(in, 0);
      }
  
      protected ConfinedInputStream(InputStream in, int lim) {
          super(in);
          this.limit = lim;
          this.consumed = 0;
      }
  
      /**
       * Returns the number of bytes not yet consumed. Note that this method doen't care about the exact number of bytes that may or may not be available in the
       * underlying {@link InputStream}
       * 
       * @return the number of bytes available.
       * @see FilterInputStream#available()
       */
      @Override
      public int available() throws IOException {
          ensureOpen();
          return this.limit - this.consumed;
      }
  
      /**
       * Closes this stream and throws away any bytes not consumed from the underlying {@link InputStream}.
       * 
       * @see FilterInputStream#close()
       */
      @Override
      public void close() throws IOException {
          // Just make sure no more bytes are left on the underlying InputStream.
          // It's up to the InputStream higher in the chain to close the underlying InputStream.
          if (!this.closed) {
              dumpLeftovers();
              this.closed = true;
          }
      }
  
      /**
       * @see FilterInputStream#read()
       */
      @Override
      public int read() throws IOException {
          ensureOpen();
          int read = super.read();
          if (read >= 0) {
              this.consumed++;
          }
          return read;
      }
  
      /**
       * Forwards the read to {@link #read(byte[], int, int)}.
       * 
       * @see FilterInputStream#read(byte[])
       */
      @Override
      public int read(byte[] b) throws IOException {
          ensureOpen();
          return read(b, 0, b.length);
      }
  
      /**
       * Reads bytes from the underlying {@link InputStream} up to the number of bytes defined in this {@link ConfinedInputStream} limit.
       * 
       * @see FilterInputStream#read(byte[], int, int)
       */
      @Override
      public int read(byte[] b, int off, int len) throws IOException {
          ensureOpen();
          if (this.consumed >= this.limit) {
              return -1;
          }
          int toRead = Math.min(len, available());
          int read = super.read(b, off, toRead);
          if (read > 0) {
              this.consumed += read;
          }
          return read;
      }
  
      /**
       * Resets this {@link ConfinedInputStream} limit so that it can be reused over the same underlying {@link InputStream}.
       * 
       * @param len
       *            the new length to set.
       * @return
       *         the number of bytes not consumed before reseting the limit.
       */
      public int resetLimit(int len) {
          int remaining = 0;
          try {
              remaining = available();
          } catch (IOException e) {
              // Won't happen.
          }
          this.limit = len;
          this.consumed = 0;
          return remaining;
      }
  
      /**
       * Skips the number bytes not yet consumed from the underlying {@link InputStream}.
       * 
       * @return the number of bytes skipped.
       * @throws IOException
       *             if any of the underlying I/O operations fail.
       */
      protected long dumpLeftovers() throws IOException {
          long skipped = skip(available());
          this.consumed += skipped;
          return skipped;
      }
  
      /**
       * Ensures that this {@link InputStream} wasn't closed yet.
       * 
       * @throws IOException
       *             if this {@link InputStream} was closed.
       */
      private void ensureOpen() throws IOException {
          if (this.closed) {
              throw new IOException("Stream closed");
          }
      }
  }
  