001 /* MBEL: The Microsoft Bytecode Engineering Library
002 * Copyright (C) 2003 The University of Arizona
003 * http://www.cs.arizona.edu/mbel/license.html
004 *
005 * This library is free software; you can redistribute it and/or
006 * modify it under the terms of the GNU Lesser General Public
007 * License as published by the Free Software Foundation; either
008 * version 2.1 of the License, or (at your option) any later version.
009 *
010 * This library is distributed in the hope that it will be useful,
011 * but WITHOUT ANY WARRANTY; without even the implied warranty of
012 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
013 * Lesser General Public License for more details.
014 *
015 * You should have received a copy of the GNU Lesser General Public
016 * License along with this library; if not, write to the Free Software
017 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
018 */
019
020 package edu.arizona.cs.mbel.metadata;
021
022 /** This class represents the user string stream in module metadata.
023 * User strings are UNICODE-16 strings, little-endian. They are single-null terminated.
024 * @author Michael Stepp
025 */
026 public class USStream{
027 // should be 4-byte aligned
028 private byte[] rawbytes;
029
030 /** Parses a USStream from an input stream, of the given size
031 * @param in the input stream
032 * @param size the size in bytes of this USStream
033 */
034 public USStream(edu.arizona.cs.mbel.MSILInputStream in, long size) throws java.io.IOException{
035 rawbytes = new byte[(int)size];
036 in.read(rawbytes);
037 }
038
039 /*
040 public void output(){
041 System.out.print("#USStream = {}");
042 }
043 */
044
045 /** Returns a string from the user string stream, indexed by byte offset
046 * @param off the byte offset within the stream of the start of the string
047 * @return the string at the given offset
048 */
049 public String getStringByOffset(long off){
050 int length;
051 int offset = (int)off;
052 if ((rawbytes[offset] & 0xC0) == 0xC0){
053 // 4byte length
054 length = ((rawbytes[offset] << 24) & 0x1F000000)
055 | ((rawbytes[offset+1] << 16) & 0x00FF0000)
056 | ((rawbytes[offset+2] << 8) & 0x0000FF00)
057 | (rawbytes[offset+3] & 0xFF);
058 offset+=4;
059 }else if ((rawbytes[offset] & 0x80) == 0x80){
060 length = ((rawbytes[offset]<<8) & 0x3F00) | (rawbytes[offset+1] & 0xFF);
061 offset+=2;
062 }else{
063 length = rawbytes[offset];
064 offset++;
065 }
066
067 String result = "";
068 for (int i=0;(i+i)<length-1;i++)
069 result += (char)(rawbytes[offset+i+i] | (rawbytes[offset+i+i+1]<<8));
070 return result;
071 }
072 }
073