/*
 *  Licensed to the Apache Software Foundation (ASF) under one or more
 *  contributor license agreements.  See the NOTICE file distributed with
 *  this work for additional information regarding copyright ownership.
 *  The ASF licenses this file to You under the Apache License, Version 2.0
 *  (the "License"); you may not use this file except in compliance with
 *  the License.  You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 */
package org.apache.ivy.plugins.pack;

import java.io.BufferedInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.zip.GZIPInputStream;

import org.apache.commons.compress.compressors.pack200.Pack200CompressorInputStream;

class Pack200Util {

  static InputStream unpack(InputStream packed) throws IOException {
    BufferedInputStream buffered = new BufferedInputStream(packed);
    buffered.mark(4);
    byte[] magic = new byte[4];
    buffered.read(magic, 0, 4);
    buffered.reset();

    InputStream in = buffered;
    if (magic[0] == (byte) 0x1F && magic[1] == (byte) 0x8B && magic[2] == (byte) 0x08) {
      // this is a gziped pack200
      in = new GZIPInputStream(in);
    }

    return new Pack200CompressorInputStream(in);
  }

}
