The BerDecoder.java Java example source code
/*
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* 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.
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package com.sun.jndi.ldap;
import java.io.UnsupportedEncodingException;
/**
* A BER decoder. Contains methods to parse a BER buffer.
*
* @author Jagane Sundar
* @author Vincent Ryan
*/
public final class BerDecoder extends Ber {
private int origOffset; // The start point in buf to decode
/**
* Creates a BER decoder that reads bytes from the specified buffer.
*/
public BerDecoder(byte buf[], int offset, int bufsize) {
this.buf = buf; // shared buffer, be careful to use this class
this.bufsize = bufsize;
this.origOffset = offset;
reset();
}
/**
* Resets this decode to start parsing from the initial offset
* (ie., same state as after calling the constructor).
*/
public void reset() {
offset = origOffset;
}
/**
* Returns the current parse position.
* It points to the byte that will be parsed next.
* Useful for parsing sequences.
*/
public int getParsePosition() {
return offset;
}
/**
* Parses a possibly variable length field.
*/
public int parseLength() throws DecodeException {
int lengthbyte = parseByte();
if ((lengthbyte & 0x80) == 0x80) {
lengthbyte &= 0x7f;
if (lengthbyte == 0) {
throw new DecodeException(
"Indefinite length not supported");
}
if (lengthbyte > 4) {
throw new DecodeException("encoding too long");
}
if (bufsize - offset < lengthbyte) {
throw new DecodeException("Insufficient data");
}
int retval = 0;
for( int i = 0; i < lengthbyte; i++) {
retval = (retval << 8) + (buf[offset++] & 0xff);
}
return retval;
} else {
return lengthbyte;
}
}
/**
* Parses the next sequence in this BER buffer.
* @param rlen An array for returning size of the sequence in bytes. If null,
* the size is not returned.
* @return The sequence's tag.
*/
public int parseSeq(int rlen[]) throws DecodeException {
int seq = parseByte();
int len = parseLength();
if (rlen != null) {
rlen[0] = len;
}
return seq;
}
/**
* Used to skip bytes. Usually used when trying to recover from parse error.
* Don't need to be public right now?
* @param i The number of bytes to skip
*/
void seek(int i) throws DecodeException {
if (offset + i > bufsize || offset + i < 0) {
throw new DecodeException("array index out of bounds");
}
offset += i;
}
/**
* Parses the next byte in this BER buffer.
* @return The byte parsed.
*/
public int parseByte() throws DecodeException {
if (bufsize - offset < 1) {
throw new DecodeException("Insufficient data");
}
return buf[offset++] & 0xff;
}
/**
* Returns the next byte in this BER buffer without consuming it.
* @return The next byte.
*/
public int peekByte() throws DecodeException {
if (bufsize - offset < 1) {
throw new DecodeException("Insufficient data");
}
return buf[offset] & 0xff;
}
/**
* Parses an ASN_BOOLEAN tagged integer from this BER buffer.
* @return true if the tagged integer is 0; false otherwise.
*/
public boolean parseBoolean() throws DecodeException {
return ((parseIntWithTag(ASN_BOOLEAN) == 0x00) ? false : true);
}
/**
* Parses an ASN_ENUMERATED tagged integer from this BER buffer.
* @return The tag of enumeration.
*/
public int parseEnumeration() throws DecodeException {
return parseIntWithTag(ASN_ENUMERATED);
}
/**
* Parses an ASN_INTEGER tagged integer from this BER buffer.
* @return The value of the integer.
*/
public int parseInt() throws DecodeException {
return parseIntWithTag(ASN_INTEGER);
}
/**
* Parses an integer that's preceded by a tag.
*<blockquote> * BER integer ::= tag length byte {byte}*
*</pre>
*/
private int parseIntWithTag(int tag) throws DecodeException {
if (parseByte() != tag) {
throw new DecodeException("Encountered ASN.1 tag " +
Integer.toString(buf[offset - 1] & 0xff) +
" (expected tag " + Integer.toString(tag) + ")");
}
int len = parseLength();
if (len > 4) {
throw new DecodeException("INTEGER too long");
} else if (len > bufsize - offset) {
throw new DecodeException("Insufficient data");
}
byte fb = buf[offset++];
int value = 0;
value = fb & 0x7F;
for( int i = 1 /* first byte already read */ ; i < len; i++) {
value <<= 8;
value |= (buf[offset++] & 0xff);
}
if ((fb & 0x80) == 0x80) {
value = -value;
}
return value;
}
/**
* Parses a string.
*/
public String parseString(boolean decodeUTF8) throws DecodeException {
return parseStringWithTag(ASN_SIMPLE_STRING, decodeUTF8, null);
}
/**
* Parses a string of a given tag from this BER buffer.
*<blockquote> *BER simple string ::= tag length {byte}*
*</pre>
* @param rlen An array for holding the relative parsed offset; if null
* offset not set.
* @param decodeUTF8 If true, use UTF-8 when decoding the string; otherwise
* use ISO-Latin-1 (8859_1). Use true for LDAPv3; false for LDAPv2.
* @param tag The tag that precedes the string.
* @return The non-null parsed string.
*/
public String parseStringWithTag(int tag, boolean decodeUTF8, int rlen[])
throws DecodeException {
int st;
int origOffset = offset;
if ((st = parseByte()) != tag) {
throw new DecodeException("Encountered ASN.1 tag " +
Integer.toString((byte)st) + " (expected tag " + tag + ")");
}
int len = parseLength();
if (len > bufsize - offset) {
throw new DecodeException("Insufficient data");
}
String retstr;
if (len == 0) {
retstr = "";
} else {
byte[] buf2 = new byte[len];
System.arraycopy(buf, offset, buf2, 0, len);
if (decodeUTF8) {
try {
retstr = new String(buf2, "UTF8");
} catch (UnsupportedEncodingException e) {
throw new DecodeException("UTF8 not available on platform");
}
} else {
try {
retstr = new String(buf2, "8859_1");
} catch (UnsupportedEncodingException e) {
throw new DecodeException("8859_1 not available on platform");
}
}
offset += len;
}
if (rlen != null) {
rlen[0] = offset - origOffset;
}
return retstr;
}
/**
* Parses an octet string of a given type(tag) from this BER buffer.
* <blockquote> * BER Binary Data of type "tag" ::= tag length {byte}*
*</pre>
*
* @param tag The tag to look for.
* @param rlen An array for returning the relative parsed position. If null,
* the relative parsed position is not returned.
* @return A non-null array containing the octet string.
* @throws DecodeException If the next byte in the BER buffer is not
* <tt>tag, or if length specified in the BER buffer exceeds the
* number of bytes left in the buffer.
*/
public byte[] parseOctetString(int tag, int rlen[]) throws DecodeException {
int origOffset = offset;
int st;
if ((st = parseByte()) != tag) {
throw new DecodeException("Encountered ASN.1 tag " +
Integer.toString(st) +
" (expected tag " + Integer.toString(tag) + ")");
}
int len = parseLength();
if (len > bufsize - offset) {
throw new DecodeException("Insufficient data");
}
byte retarr[] = new byte[len];
if (len > 0) {
System.arraycopy(buf, offset, retarr, 0, len);
offset += len;
}
if (rlen != null) {
rlen[0] = offset - origOffset;
}
return retarr;
}
/**
* Returns the number of unparsed bytes in this BER buffer.
*/
public int bytesLeft() {
return bufsize - offset;
}
}
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