| /** |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| * |
| */ |
| package org.apache.kerby.asn1.parse; |
| |
| import org.apache.kerby.asn1.Tag; |
| |
| import java.io.IOException; |
| import java.nio.ByteBuffer; |
| |
| /** |
| * ASN1 reader for positional reading. |
| */ |
| public final class Asn1Reader { |
| private ByteBuffer buffer; |
| private int position; |
| |
| public ByteBuffer getBuffer() { |
| return buffer; |
| } |
| |
| public Asn1Header readHeader() throws IOException { |
| Tag tag = readTag(); |
| int valueLength = readLength(); |
| Asn1Header header = new Asn1Header(tag, valueLength); |
| return header; |
| } |
| |
| public Asn1Reader(ByteBuffer buffer) { |
| this.buffer = buffer; |
| this.position = buffer.position(); |
| } |
| |
| public int getPosition() { |
| return position; |
| } |
| |
| public void setPosition(int position) { |
| this.position = position; |
| } |
| |
| public boolean available() { |
| return position < buffer.limit(); |
| } |
| |
| protected byte readByte() throws IOException { |
| return buffer.get(position++); |
| } |
| |
| private Tag readTag() throws IOException { |
| int tagFlags = readTagFlags(); |
| int tagNo = readTagNo(tagFlags); |
| return new Tag(tagFlags, tagNo); |
| } |
| |
| private int readTagFlags() throws IOException { |
| int tagFlags = readByte() & 0xff; |
| return tagFlags; |
| } |
| |
| private int readTagNo(int tagFlags) throws IOException { |
| int tagNo = tagFlags & 0x1f; |
| |
| if (tagNo == 0x1f) { |
| tagNo = 0; |
| |
| int b = readByte() & 0xff; |
| if ((b & 0x7f) == 0) { |
| throw new IOException("Invalid high tag number found"); |
| } |
| |
| while (b >= 0 && (b & 0x80) != 0) { |
| tagNo |= b & 0x7f; |
| tagNo <<= 7; |
| b = readByte(); |
| } |
| |
| tagNo |= b & 0x7f; |
| } |
| |
| return tagNo; |
| } |
| |
| private int readLength() throws IOException { |
| int result = readByte() & 0xff; |
| if (result == 0x80) { |
| return -1; // non-definitive length |
| } |
| |
| if (result > 127) { |
| int length = result & 0x7f; |
| if (length > 4) { |
| throw new IOException("Bad length of more than 4 bytes: " + length); |
| } |
| |
| result = 0; |
| int tmp; |
| for (int i = 0; i < length; i++) { |
| tmp = readByte() & 0xff; |
| result = (result << 8) + tmp; |
| } |
| } |
| |
| if (result < 0) { |
| throw new IOException("Invalid length " + result); |
| } |
| |
| return result; |
| } |
| } |