content: /*
   * Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.  Oracle designates this
   * particular file as subject to the "Classpath" exception as provided
   * by Oracle in the LICENSE file that accompanied this code.
   *
   * This code 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 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   */
  
  package java.util.zip;
  
  import java.io.OutputStream;
  import java.io.IOException;
  
  /**
   * This class implements a stream filter for writing compressed data in
   * the GZIP file format.
   * @author      David Connelly
   *
   */
  public
  class GZIPOutputStream extends DeflaterOutputStream {
      /**
       * CRC-32 of uncompressed data.
       */
      protected CRC32 crc = new CRC32();
  
      /*
       * GZIP header magic number.
       */
      private final static int GZIP_MAGIC = 0x8b1f;
  
      /*
       * Trailer size in bytes.
       *
       */
      private final static int TRAILER_SIZE = 8;
  
      /**
       * Creates a new output stream with the specified buffer size.
       *
       * <p>The new output stream instance is created as if by invoking
       * the 3-argument constructor GZIPOutputStream(out, size, false).
       *
       * @param out the output stream
       * @param size the output buffer size
       * @exception IOException If an I/O error has occurred.
       * @exception IllegalArgumentException if {@code size <= 0}
       */
      public GZIPOutputStream(OutputStream out, int size) throws IOException {
          this(out, size, false);
      }
  
      /**
       * Creates a new output stream with the specified buffer size and
       * flush mode.
       *
       * @param out the output stream
       * @param size the output buffer size
       * @param syncFlush
       *        if {@code true} invocation of the inherited
       *        {@link DeflaterOutputStream#flush() flush()} method of
       *        this instance flushes the compressor with flush mode
       *        {@link Deflater#SYNC_FLUSH} before flushing the output
       *        stream, otherwise only flushes the output stream
       * @exception IOException If an I/O error has occurred.
       * @exception IllegalArgumentException if {@code size <= 0}
       *
       * @since 1.7
       */
      public GZIPOutputStream(OutputStream out, int size, boolean syncFlush)
          throws IOException
      {
          super(out, new Deflater(Deflater.DEFAULT_COMPRESSION, true),
                size,
                syncFlush);
          usesDefaultDeflater = true;
          writeHeader();
          crc.reset();
      }
  
  
      /**
       * Creates a new output stream with a default buffer size.
       *
       * <p>The new output stream instance is created as if by invoking
       * the 2-argument constructor GZIPOutputStream(out, false).
       *
       * @param out the output stream
       * @exception IOException If an I/O error has occurred.
       */
      public GZIPOutputStream(OutputStream out) throws IOException {
          this(out, 512, false);
      }
  
      /**
       * Creates a new output stream with a default buffer size and
       * the specified flush mode.
       *
       * @param out the output stream
       * @param syncFlush
       *        if {@code true} invocation of the inherited
       *        {@link DeflaterOutputStream#flush() flush()} method of
       *        this instance flushes the compressor with flush mode
       *        {@link Deflater#SYNC_FLUSH} before flushing the output
       *        stream, otherwise only flushes the output stream
       *
       * @exception IOException If an I/O error has occurred.
       *
       * @since 1.7
       */
      public GZIPOutputStream(OutputStream out, boolean syncFlush)
          throws IOException
      {
          this(out, 512, syncFlush);
      }
  
      /**
       * Writes array of bytes to the compressed output stream. This method
       * will block until all the bytes are written.
       * @param buf the data to be written
       * @param off the start offset of the data
       * @param len the length of the data
       * @exception IOException If an I/O error has occurred.
       */
      public synchronized void write(byte[] buf, int off, int len)
          throws IOException
      {
          super.write(buf, off, len);
          crc.update(buf, off, len);
      }
  
      /**
       * Finishes writing compressed data to the output stream without closing
       * the underlying stream. Use this method when applying multiple filters
       * in succession to the same output stream.
       * @exception IOException if an I/O error has occurred
       */
      public void finish() throws IOException {
          if (!def.finished()) {
              def.finish();
              while (!def.finished()) {
                  int len = def.deflate(buf, 0, buf.length);
                  if (def.finished() && len <= buf.length - TRAILER_SIZE) {
                      // last deflater buffer. Fit trailer at the end
                      writeTrailer(buf, len);
                      len = len + TRAILER_SIZE;
                      out.write(buf, 0, len);
                      return;
                  }
                  if (len > 0)
                      out.write(buf, 0, len);
              }
              // if we can't fit the trailer at the end of the last
              // deflater buffer, we write it separately
              byte[] trailer = new byte[TRAILER_SIZE];
              writeTrailer(trailer, 0);
              out.write(trailer);
          }
      }
  
      /*
       * Writes GZIP member header.
       */
      private void writeHeader() throws IOException {
          out.write(new byte[] {
                        (byte) GZIP_MAGIC,        // Magic number (short)
                        (byte)(GZIP_MAGIC >> 8),  // Magic number (short)
                        Deflater.DEFLATED,        // Compression method (CM)
                        0,                        // Flags (FLG)
                        0,                        // Modification time MTIME (int)
                        0,                        // Modification time MTIME (int)
                        0,                        // Modification time MTIME (int)
                        0,                        // Modification time MTIME (int)
                        0,                        // Extra flags (XFLG)
                        0                         // Operating system (OS)
                    });
      }
  
      /*
       * Writes GZIP member trailer to a byte array, starting at a given
       * offset.
       */
      private void writeTrailer(byte[] buf, int offset) throws IOException {
          writeInt((int)crc.getValue(), buf, offset); // CRC-32 of uncompr. data
          writeInt(def.getTotalIn(), buf, offset + 4); // Number of uncompr. bytes
      }
  
      /*
       * Writes integer in Intel byte order to a byte array, starting at a
       * given offset.
       */
      private void writeInt(int i, byte[] buf, int offset) throws IOException {
          writeShort(i & 0xffff, buf, offset);
          writeShort((i >> 16) & 0xffff, buf, offset + 2);
      }
  
      /*
       * Writes short integer in Intel byte order to a byte array, starting
       * at a given offset
       */
      private void writeShort(int s, byte[] buf, int offset) throws IOException {
          buf[offset] = (byte)(s & 0xff);
          buf[offset + 1] = (byte)((s >> 8) & 0xff);
      }
  }
  