content: /*******************************************************************************
   * Copyright (c) 2009, 2019 Mountainminds GmbH & Co. KG and Contributors
   * All rights reserved. This program and the accompanying materials
   * are made available under the terms of the Eclipse Public License v1.0
   * which accompanies this distribution, and is available at
   * http://www.eclipse.org/legal/epl-v10.html
   *
   * Contributors:
   *    Marc R. Hoffmann - initial API and implementation
   *    
   *******************************************************************************/
  package org.jacoco.core.internal;
  
  import java.io.BufferedInputStream;
  import java.io.IOException;
  import java.io.InputStream;
  
  import org.objectweb.asm.Opcodes;
  
  /**
   * Detector for content types of binary streams based on a magic headers.
   */
  public class ContentTypeDetector {
  
  	/** Unknown file type */
  	public static final int UNKNOWN = -1;
  
  	/** File type Java class */
  	public static final int CLASSFILE = 0xcafebabe;
  
  	/** File type ZIP archive */
  	public static final int ZIPFILE = 0x504b0304;
  
  	/** File type GZIP compressed Data */
  	public static final int GZFILE = 0x1f8b0000;
  
  	/** File type Pack200 archive */
  	public static final int PACK200FILE = 0xcafed00d;
  
  	private static final int BUFFER_SIZE = 8;
  
  	private final InputStream in;
  
  	private final int type;
  
  	/**
  	 * Creates a new detector based on the given input. To process the complete
  	 * original input afterwards use the stream returned by
  	 * {@link #getInputStream()}.
  	 * 
  	 * @param in
  	 *            input to read the header from
  	 * @throws IOException
  	 *             if the stream can't be read
  	 */
  	public ContentTypeDetector(final InputStream in) throws IOException {
  		if (in.markSupported()) {
  			this.in = in;
  		} else {
  			this.in = new BufferedInputStream(in, BUFFER_SIZE);
  		}
  		this.in.mark(BUFFER_SIZE);
  		this.type = determineType(this.in);
  		this.in.reset();
  	}
  
  	private static int determineType(final InputStream in) throws IOException {
  		final int header = readInt(in);
  		switch (header) {
  		case ZIPFILE:
  			return ZIPFILE;
  		case PACK200FILE:
  			return PACK200FILE;
  		case CLASSFILE:
  			// also verify version to distinguish from Mach Object files:
  			switch (readInt(in)) {
  			case Opcodes.V1_1:
  			case Opcodes.V1_2:
  			case Opcodes.V1_3:
  			case Opcodes.V1_4:
  			case Opcodes.V1_5:
  			case Opcodes.V1_6:
  			case Opcodes.V1_7:
  			case Opcodes.V1_8:
  			case Opcodes.V9:
  			case Opcodes.V10:
  			case Opcodes.V11:
  			case Opcodes.V11 | Opcodes.V_PREVIEW:
  			case Opcodes.V12:
  			case Opcodes.V12 | Opcodes.V_PREVIEW:
  			case (Opcodes.V12 + 1):
  			case (Opcodes.V12 + 1) | Opcodes.V_PREVIEW:
  				return CLASSFILE;
  			}
  		}
  		if ((header & 0xffff0000) == GZFILE) {
  			return GZFILE;
  		}
  		return UNKNOWN;
  	}
  
  	private static int readInt(final InputStream in) throws IOException {
  		return in.read() << 24 | in.read() << 16 | in.read() << 8 | in.read();
  	}
  
  	/**
  	 * Returns an input stream instance to read the complete content (including
  	 * the header) of the underlying stream.
  	 * 
  	 * @return input stream containing the complete content
  	 */
  	public InputStream getInputStream() {
  		return in;
  	}
  
  	/**
  	 * Returns the detected file type.
  	 * 
  	 * @return file type
  	 */
  	public int getType() {
  		return type;
  	}
  
  }
  