| // Copyright (c) 2004 Brian Wellington (bwelling@xbill.org) |
| |
| package org.xbill.DNS; |
| |
| /** |
| * An class for parsing DNS messages. |
| * |
| * @author Brian Wellington |
| */ |
| |
| public class DNSInput { |
| |
| private byte [] array; |
| private int pos; |
| private int end; |
| private int saved_pos; |
| private int saved_end; |
| |
| /** |
| * Creates a new DNSInput |
| * @param input The byte array to read from |
| */ |
| public |
| DNSInput(byte [] input) { |
| array = input; |
| pos = 0; |
| end = array.length; |
| saved_pos = -1; |
| saved_end = -1; |
| } |
| |
| /** |
| * Returns the current position. |
| */ |
| public int |
| current() { |
| return pos; |
| } |
| |
| /** |
| * Returns the number of bytes that can be read from this stream before |
| * reaching the end. |
| */ |
| public int |
| remaining() { |
| return end - pos; |
| } |
| |
| private void |
| require(int n) throws WireParseException{ |
| if (n > remaining()) { |
| throw new WireParseException("end of input"); |
| } |
| } |
| |
| /** |
| * Marks the following bytes in the stream as active. |
| * @param len The number of bytes in the active region. |
| * @throws IllegalArgumentException The number of bytes in the active region |
| * is longer than the remainder of the input. |
| */ |
| public void |
| setActive(int len) { |
| if (len > array.length - pos) { |
| throw new IllegalArgumentException("cannot set active " + |
| "region past end of input"); |
| } |
| end = pos + len; |
| } |
| |
| /** |
| * Clears the active region of the string. Further operations are not |
| * restricted to part of the input. |
| */ |
| public void |
| clearActive() { |
| end = array.length; |
| } |
| |
| /** |
| * Returns the position of the end of the current active region. |
| */ |
| public int |
| saveActive() { |
| return end; |
| } |
| |
| /** |
| * Restores the previously set active region. This differs from setActive() in |
| * that restoreActive() takes an absolute position, and setActive takes an |
| * offset from the current location. |
| * @param pos The end of the active region. |
| */ |
| public void |
| restoreActive(int pos) { |
| if (pos > array.length) { |
| throw new IllegalArgumentException("cannot set active " + |
| "region past end of input"); |
| } |
| end = pos; |
| } |
| |
| /** |
| * Resets the current position of the input stream to the specified index, |
| * and clears the active region. |
| * @param index The position to continue parsing at. |
| * @throws IllegalArgumentException The index is not within the input. |
| */ |
| public void |
| jump(int index) { |
| if (index >= array.length) { |
| throw new IllegalArgumentException("cannot jump past " + |
| "end of input"); |
| } |
| pos = index; |
| end = array.length; |
| } |
| |
| /** |
| * Saves the current state of the input stream. Both the current position and |
| * the end of the active region are saved. |
| * @throws IllegalArgumentException The index is not within the input. |
| */ |
| public void |
| save() { |
| saved_pos = pos; |
| saved_end = end; |
| } |
| |
| /** |
| * Restores the input stream to its state before the call to {@link #save}. |
| */ |
| public void |
| restore() { |
| if (saved_pos < 0) { |
| throw new IllegalStateException("no previous state"); |
| } |
| pos = saved_pos; |
| end = saved_end; |
| saved_pos = -1; |
| saved_end = -1; |
| } |
| |
| /** |
| * Reads an unsigned 8 bit value from the stream, as an int. |
| * @return An unsigned 8 bit value. |
| * @throws WireParseException The end of the stream was reached. |
| */ |
| public int |
| readU8() throws WireParseException { |
| require(1); |
| return (array[pos++] & 0xFF); |
| } |
| |
| /** |
| * Reads an unsigned 16 bit value from the stream, as an int. |
| * @return An unsigned 16 bit value. |
| * @throws WireParseException The end of the stream was reached. |
| */ |
| public int |
| readU16() throws WireParseException { |
| require(2); |
| int b1 = array[pos++] & 0xFF; |
| int b2 = array[pos++] & 0xFF; |
| return ((b1 << 8) + b2); |
| } |
| |
| /** |
| * Reads an unsigned 32 bit value from the stream, as a long. |
| * @return An unsigned 32 bit value. |
| * @throws WireParseException The end of the stream was reached. |
| */ |
| public long |
| readU32() throws WireParseException { |
| require(4); |
| int b1 = array[pos++] & 0xFF; |
| int b2 = array[pos++] & 0xFF; |
| int b3 = array[pos++] & 0xFF; |
| int b4 = array[pos++] & 0xFF; |
| return (((long)b1 << 24) + (b2 << 16) + (b3 << 8) + b4); |
| } |
| |
| /** |
| * Reads a byte array of a specified length from the stream into an existing |
| * array. |
| * @param b The array to read into. |
| * @param off The offset of the array to start copying data into. |
| * @param len The number of bytes to copy. |
| * @throws WireParseException The end of the stream was reached. |
| */ |
| public void |
| readByteArray(byte [] b, int off, int len) throws WireParseException { |
| require(len); |
| System.arraycopy(array, pos, b, off, len); |
| pos += len; |
| } |
| |
| /** |
| * Reads a byte array of a specified length from the stream. |
| * @return The byte array. |
| * @throws WireParseException The end of the stream was reached. |
| */ |
| public byte [] |
| readByteArray(int len) throws WireParseException { |
| require(len); |
| byte [] out = new byte[len]; |
| System.arraycopy(array, pos, out, 0, len); |
| pos += len; |
| return out; |
| } |
| |
| /** |
| * Reads a byte array consisting of the remainder of the stream (or the |
| * active region, if one is set. |
| * @return The byte array. |
| */ |
| public byte [] |
| readByteArray() { |
| int len = remaining(); |
| byte [] out = new byte[len]; |
| System.arraycopy(array, pos, out, 0, len); |
| pos += len; |
| return out; |
| } |
| |
| /** |
| * Reads a counted string from the stream. A counted string is a one byte |
| * value indicating string length, followed by bytes of data. |
| * @return A byte array containing the string. |
| * @throws WireParseException The end of the stream was reached. |
| */ |
| public byte [] |
| readCountedString() throws WireParseException { |
| require(1); |
| int len = array[pos++] & 0xFF; |
| return readByteArray(len); |
| } |
| |
| } |