/* * Copyright (c) 1997, 2007, 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 com.sun.jmx.snmp;    /** * The <CODE>BerDecoder</CODE> class is used for decoding * BER-encoded data. * * A <CODE>BerDecoder</CODE> needs to be set up with the byte string containing * the encoding. It maintains a current position in the byte string. * * Methods allows to fetch integer, string, OID, etc., from the current * position. After a fetch the current position is moved forward. * * A fetch throws a <CODE>BerException</CODE> if the encoding is not of the * expected type. * * <p><b>This API is a Sun Microsystems internal API  and is subject * to change without notice.</b></p> * * @since 1.5 */ public class BerDecoder {   /**  * Constructs a new decoder and attaches it to the specified byte string.  *  * @param b The byte string containing the encoded data.  */   public BerDecoder(byte b[]) {    bytes = b ;    reset() ;  }   public void reset() {    next = 0 ;    stackTop = 0 ;  }   /**  * Fetch an integer.  *  * @return The decoded integer.  *  * @exception BerException Current position does not point to an integer.  */   public int fetchInteger() throws BerException {    return fetchInteger(IntegerTag) ;  }    /**  * Fetch an integer with the specified tag.  *  * @param tag The expected tag.  *  * @return The decoded integer.  *  * @exception BerException Current position does not point to an integer  *                         or the tag is not the expected one.  */   public int fetchInteger(int tag) throws BerException {    int result = 0 ;    final int backup = next ;    try {      if (fetchTag() != tag) {        throw new BerException() ;      }      result = fetchIntegerValue() ;    }    catch(BerException e) {      next = backup ;      throw e ;    }     return result ;  }     /**  * Fetch an integer and return a long value.  *  * @return The decoded integer.  *  * @exception BerException Current position does not point to an integer.  */   public long fetchIntegerAsLong() throws BerException {    return fetchIntegerAsLong(IntegerTag) ;  }    /**  * Fetch an integer with the specified tag and return a long value.  *  * @param tag The expected tag.  *  * @return The decoded integer.  *  * @exception BerException Current position does not point to an integer  *                         or the tag is not the expected one.  */   public long fetchIntegerAsLong(int tag) throws BerException {    long result = 0 ;    final int backup = next ;    try {      if (fetchTag() != tag) {        throw new BerException() ;      }      result = fetchIntegerValueAsLong() ;    }    catch(BerException e) {      next = backup ;      throw e ;    }     return result ;  }     /**  * Fetch an octet string.  *  * @return The decoded string.  *  * @exception BerException Current position does not point to an octet string.  */   public byte[] fetchOctetString() throws BerException {    return fetchOctetString(OctetStringTag) ;  }    /**  * Fetch an octet string with a specified tag.  *  * @param tag The expected tag.  *  * @return The decoded string.  *  * @exception BerException Current position does not point to an octet string  *                         or the tag is not the expected one.  */   public byte[] fetchOctetString(int tag) throws BerException {    byte[] result = null ;    final int backup = next ;    try {      if (fetchTag() != tag) {        throw new BerException() ;      }      result = fetchStringValue() ;    }    catch(BerException e) {      next = backup ;      throw e ;    }     return result ;  }    /**  * Fetch an object identifier.  *  * @return The decoded object identifier as an array of long.  */   public long[] fetchOid() throws BerException {    return fetchOid(OidTag) ;  }    /**  * Fetch an object identifier with a specified tag.  *  * @param tag The expected tag.  *  * @return The decoded object identifier as an array of long.  *  * @exception BerException Current position does not point to an oid  *                         or the tag is not the expected one.  */   public long[] fetchOid(int tag) throws BerException {    long[] result = null ;    final int backup = next ;    try {      if (fetchTag() != tag) {        throw new BerException() ;      }      result = fetchOidValue() ;    }    catch(BerException e) {      next = backup ;      throw e ;    }     return result ;  }    /**  * Fetch a <CODE>NULL</CODE> value.  *  * @exception BerException Current position does not point to <CODE>NULL</CODE> value.  */   public void fetchNull() throws BerException {    fetchNull(NullTag) ;  }    /**  * Fetch a <CODE>NULL</CODE> value with a specified tag.  *  * @param tag The expected tag.  *  * @exception BerException Current position does not point to  *            <CODE>NULL</CODE> value or the tag is not the expected one.  */   public void fetchNull(int tag) throws BerException {    final int backup = next ;    try {      if (fetchTag() != tag) {        throw new BerException() ;      }      final int length = fetchLength();      if (length != 0) throw new BerException();    }    catch(BerException e) {      next = backup ;      throw e ;    }  }     /**  * Fetch an <CODE>ANY</CODE> value. In fact, this method does not decode anything  * it simply returns the next TLV as an array of bytes.  *  * @return The TLV as a byte array.  *  * @exception BerException The next TLV is really badly encoded...  */   public byte[] fetchAny() throws BerException {    byte[] result = null ;    final int backup = next ;    try {      final int tag = fetchTag() ;      final int contentLength = fetchLength() ;      if (contentLength < 0) throw new BerException() ;      final int tlvLength = next + contentLength - backup ;      if (contentLength > (bytes.length - next))          throw new IndexOutOfBoundsException("Decoded length exceeds buffer");      final byte[] data = new byte[tlvLength] ;      java.lang.System.arraycopy(bytes,backup,data,0,tlvLength);      // for (int i = 0 ; i < tlvLength ; i++) {      //  data[i] = bytes[backup + i] ;      // }      next = next + contentLength ;      result = data;    }    catch(IndexOutOfBoundsException e) {      next = backup ;      throw new BerException() ;    }    // catch(Error e) {    //    debug("fetchAny: Error decoding BER: " + e);    //    throw e;    // }     return result ;  }    /**  * Fetch an <CODE>ANY</CODE> value with a specific tag.  *  * @param tag The expected tag.  *  * @return The TLV as a byte array.  *  * @exception BerException The next TLV is really badly encoded...  */   public byte[] fetchAny(int tag) throws BerException {    if (getTag() != tag) {      throw new BerException() ;    }    return fetchAny() ;  }     /**  * Fetch a sequence header.  * The decoder computes the end position of the sequence and push it  * on its stack.  *  * @exception BerException Current position does not point to a sequence header.  */   public void openSequence() throws BerException {    openSequence(SequenceTag) ;  }    /**  * Fetch a sequence header with a specific tag.  *  * @param tag The expected tag.  *  * @exception BerException Current position does not point to a sequence header  *                         or the tag is not the expected one.  */   public void openSequence(int tag) throws BerException {    final int backup = next ;    try {      if (fetchTag() != tag) {        throw new BerException() ;      }      final int l = fetchLength() ;      if (l < 0) throw new BerException();      if (l > (bytes.length - next)) throw new BerException();      stackBuf[stackTop++] = next + l ;    }    catch(BerException e) {      next = backup ;      throw e ;    }  }    /**  * Close a sequence.  * The decode pull the stack and verifies that the current position  * matches with the calculated end of the sequence. If not it throws  * an exception.  *  * @exception BerException The sequence is not expected to finish here.  */   public void closeSequence() throws BerException {    if (stackBuf[stackTop - 1] == next) {      stackTop-- ;    }    else {      throw new BerException() ;    }  }    /**  * Return <CODE>true</CODE> if the end of the current sequence is not reached.  * When this method returns <CODE>false</CODE>, <CODE>closeSequence</CODE> can (and must) be  * invoked.  *  * @return <CODE>true</CODE> if there is still some data in the sequence.  */   public boolean cannotCloseSequence() {    return (next < stackBuf[stackTop - 1]) ;  }    /**  * Get the tag of the data at the current position.  * Current position is unchanged.  *  * @return The next tag.  */   public int getTag() throws BerException {    int result = 0 ;    final int backup = next ;    try {      result = fetchTag() ;    }    finally {      next = backup ;    }     return result ;  }     public String toString() {    final StringBuffer result = new StringBuffer(bytes.length * 2) ;    for (int i = 0 ; i < bytes.length ; i++) {      final int b = (bytes[i] > 0) ? bytes[i] : bytes[i] + 256 ;      if (i == next) {        result.append("(") ;      }      result.append(Character.forDigit(b / 16, 16)) ;      result.append(Character.forDigit(b % 16, 16)) ;      if (i == next) {        result.append(")") ;      }    }    if (bytes.length == next) {      result.append("()") ;    }     return new String(result) ;  }    //  // Some standard tags  //  public final static int BooleanTag      = 1 ;  public final static int IntegerTag      = 2 ;  public final static int OctetStringTag  = 4 ;  public final static int NullTag          = 5 ;  public final static int OidTag          = 6 ;  public final static int SequenceTag      = 0x30 ;      ////////////////////////// PRIVATE ///////////////////////////////     /**  * Fetch a tag and move the current position forward.  *  * @return The tag  */   private final int fetchTag() throws BerException {    int result = 0 ;    final int backup = next ;     try {      final byte b0 = bytes[next++] ;      result = (b0 >= 0) ? b0 : b0 + 256 ;      if ((result & 31) == 31) {        while ((bytes[next] & 128) != 0) {          result = result << 7 ;          result = result | (bytes[next++] & 127);        }      }    }    catch(IndexOutOfBoundsException e) {      next = backup ;      throw new BerException() ;    }     return result ;  }    /**  * Fetch a length and move the current position forward.  *  * @return The length  */   private final int fetchLength() throws BerException {

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