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package com.sun.jmx.snmp;




The BerDecoder class is used for decoding BER-encoded data. A BerDecoder 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 BerException if the encoding is not of the expected type.

This API is a Sun Microsystems internal API and is subject to change without notice.

Since:1.5
/** * 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.
Params:
  • b – The byte string containing the encoded data.
/** * 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.
Throws:
  • BerException – Current position does not point to an integer.
Returns:The decoded integer.
/** * 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.
Params:
  • tag – The expected tag.
Throws:
  • BerException – Current position does not point to an integer or the tag is not the expected one.
Returns:The decoded integer.
/** * 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.
Throws:
  • BerException – Current position does not point to an integer.
Returns:The decoded integer.
/** * 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.
Params:
  • tag – The expected tag.
Throws:
  • BerException – Current position does not point to an integer or the tag is not the expected one.
Returns:The decoded integer.
/** * 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.
Throws:
  • BerException – Current position does not point to an octet string.
Returns:The decoded string.
/** * 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.
Params:
  • tag – The expected tag.
Throws:
  • BerException – Current position does not point to an octet string or the tag is not the expected one.
Returns:The decoded string.
/** * 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.
Returns:The decoded object identifier as an array of long.
/** * 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.
Params:
  • tag – The expected tag.
Throws:
  • BerException – Current position does not point to an oid or the tag is not the expected one.
Returns:The decoded object identifier as an array of long.
/** * 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 NULL value.
Throws:
  • BerException – Current position does not point to NULL value.
/** * 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 NULL value with a specified tag.
Params:
  • tag – The expected tag.
Throws:
  • BerException – Current position does not point to NULL value or the tag is not the expected one.
/** * 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 ANY value. In fact, this method does not decode anything it simply returns the next TLV as an array of bytes.
Throws:
Returns:The TLV as a byte array.
/** * 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 ANY value with a specific tag.
Params:
  • tag – The expected tag.
Throws:
Returns:The TLV as a byte array.
/** * 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.
Throws:
  • BerException – Current position does not point to a sequence header.
/** * 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.
Params:
  • tag – The expected tag.
Throws:
  • BerException – Current position does not point to a sequence header or the tag is not the expected one.
/** * 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.
Throws:
  • BerException – The sequence is not expected to finish here.
/** * 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 true if the end of the current sequence is not reached. When this method returns false, closeSequence can (and must) be invoked.
Returns:true if there is still some data in the sequence.
/** * 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.
Returns:The next tag.
/** * 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.
Returns:The tag
/** * 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.
Returns:The length
/** * Fetch a length and move the current position forward. * * @return The length */
private final int fetchLength() throws BerException { int result = 0 ; final int backup = next ; try { final byte b0 = bytes[next++] ; if (b0 >= 0) { result = b0 ; } else { for (int c = 128 + b0 ; c > 0 ; c--) { final byte bX = bytes[next++] ; result = result << 8 ; result = result | ((bX >= 0) ? bX : bX+256) ; } } } catch(IndexOutOfBoundsException e) { next = backup ; throw new BerException() ; } return result ; }
Fetch an integer value and move the current position forward.
Returns:The integer
/** * Fetch an integer value and move the current position forward. * * @return The integer */
private int fetchIntegerValue() throws BerException { int result = 0 ; final int backup = next ; try { final int length = fetchLength() ; if (length <= 0) throw new BerException() ; if (length > (bytes.length - next)) throw new IndexOutOfBoundsException("Decoded length exceeds buffer"); final int end = next + length ; result = bytes[next++] ; while (next < end) { final byte b = bytes[next++] ; if (b < 0) { result = (result << 8) | (256 + b) ; } else { result = (result << 8) | b ; } } } catch(BerException e) { next = backup ; throw e ; } catch(IndexOutOfBoundsException e) { next = backup ; throw new BerException() ; } catch(ArithmeticException e) { next = backup ; throw new BerException() ; } return result ; }
Fetch an integer value and return a long value. FIX ME: someday we could have only on fetchIntegerValue() which always returns a long value.
Returns:The integer
/** * Fetch an integer value and return a long value. * FIX ME: someday we could have only on fetchIntegerValue() which always * returns a long value. * * @return The integer */
private final long fetchIntegerValueAsLong() throws BerException { long result = 0 ; final int backup = next ; try { final int length = fetchLength() ; if (length <= 0) throw new BerException() ; if (length > (bytes.length - next)) throw new IndexOutOfBoundsException("Decoded length exceeds buffer"); final int end = next + length ; result = bytes[next++] ; while (next < end) { final byte b = bytes[next++] ; if (b < 0) { result = (result << 8) | (256 + b) ; } else { result = (result << 8) | b ; } } } catch(BerException e) { next = backup ; throw e ; } catch(IndexOutOfBoundsException e) { next = backup ; throw new BerException() ; } catch(ArithmeticException e) { next = backup ; throw new BerException() ; } return result ; }
Fetch a byte string and move the current position forward.
Returns:The byte string
/** * Fetch a byte string and move the current position forward. * * @return The byte string */
private byte[] fetchStringValue() throws BerException { byte[] result = null ; final int backup = next ; try { final int length = fetchLength() ; if (length < 0) throw new BerException() ; if (length > (bytes.length - next)) throw new IndexOutOfBoundsException("Decoded length exceeds buffer"); final byte data[] = new byte[length] ; java.lang.System.arraycopy(bytes,next,data,0,length); next += length; // int i = 0 ; // while (i < length) { // result[i++] = bytes[next++] ; // } result = data; } catch(BerException e) { next = backup ; throw e ; } catch(IndexOutOfBoundsException e) { next = backup ; throw new BerException() ; } catch(ArithmeticException e) { next = backup ; throw new BerException() ; } // catch(Error e) { // debug("fetchStringValue: Error decoding BER: " + e); // throw e; // } return result ; }
Fetch an oid and move the current position forward.
Returns:The oid
/** * Fetch an oid and move the current position forward. * * @return The oid */
private final long[] fetchOidValue() throws BerException { long[] result = null ; final int backup = next ; try { final int length = fetchLength() ; if (length <= 0) throw new BerException() ; if (length > (bytes.length - next)) throw new IndexOutOfBoundsException("Decoded length exceeds buffer"); // Count how many bytes have their 8th bit to 0 // -> this gives the number of components in the oid int subidCount = 2 ; for (int i = 1 ; i < length ; i++) { if ((bytes[next + i] & 0x80) == 0) { subidCount++ ; } } final int datalen = subidCount; final long[] data = new long[datalen]; final byte b0 = bytes[next++] ; // bugId 4641746 // The 8th bit of the first byte should always be set to 0 if (b0 < 0) throw new BerException(); // bugId 4641746 // The first sub Id cannot be greater than 2 final long lb0 = b0 / 40 ; if (lb0 > 2) throw new BerException(); final long lb1 = b0 % 40; data[0] = lb0 ; data[1] = lb1 ; int i = 2 ; while (i < datalen) { long subid = 0 ; byte b = bytes[next++] ; while ((b & 0x80) != 0) { subid = (subid << 7) | (b & 0x7f) ; // bugId 4654674 if (subid < 0) throw new BerException(); b = bytes[next++] ; } subid = (subid << 7) | b ; // bugId 4654674 if (subid < 0) throw new BerException(); data[i++] = subid ; } result = data; } catch(BerException e) { next = backup ; throw e ; } catch(IndexOutOfBoundsException e) { next = backup ; throw new BerException() ; } // catch(Error e) { // debug("fetchOidValue: Error decoding BER: " + e); // throw e; // } return result ; } // private static final void debug(String str) { // System.out.println(str); // } // // This is the byte array containing the encoding. // private final byte bytes[]; // // This is the current location. It is the next byte // to be decoded. It's an index in bytes[]. // private int next = 0 ; // // This is the stack where end of sequences are kept. // A value is computed and pushed in it each time openSequence() // is invoked. // A value is pulled and checked each time closeSequence() is called. // private final int stackBuf[] = new int[200] ; private int stackTop = 0 ; }