1 /*
2 * Copyright 2005 The Apache Software Foundation
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 *
16 */
17 package org.apache.asn1new.ber.grammar;
18
19 import org.apache.asn1new.Asn1Object;
20 import org.apache.asn1.codec.DecoderException;
21 import org.apache.asn1new.ber.containers.IAsn1Container;
22 import org.apache.asn1new.ber.tlv.TLV;
23 import org.apache.asn1new.ber.tlv.Tag;
24 import org.apache.asn1new.util.StringUtils;
25 import org.slf4j.LoggerFactory;
26
27 import org.slf4j.Logger;
28
29
30 /**
31 * The abstract IGrammar which is the Mother of all the grammars. It
32 * contains the transitions table.
33 *
34 * @author <a href="mailto:dev@directory.apache.org">Apache Directory Project</a>
35 */
36 public abstract class AbstractGrammar implements IGrammar
37 {
38 //~ Static fields/initializers -----------------------------------------------------------------
39
40 /** The logger */
41 private static final Logger log = LoggerFactory.getLogger( AbstractGrammar.class );
42
43 /** A speedup for logs */
44 private static boolean DEBUG;
45
46 //~ Instance fields ----------------------------------------------------------------------------
47
48 /** Table of transitions. It's a two dimension array, the first dimension
49 * indice the states, the second dimension indices the Tag value, so it is 256 wide. */
50 protected GrammarTransition[][] transitions;
51
52 /** The grammar name */
53 protected String name;
54
55 /** The grammar's states */
56 protected IStates statesEnum;
57
58 public AbstractGrammar()
59 {
60 DEBUG = log.isDebugEnabled();
61 }
62
63 //~ Methods ------------------------------------------------------------------------------------
64
65 /**
66 * Return the grammar's name
67 * @return The grammar name
68 */
69 public String getName()
70 {
71 return name;
72 }
73
74 /**
75 * Set the grammar's name
76 * @param name DOCUMENT ME!
77 */
78 public void setName( String name )
79 {
80 this.name = name;
81 }
82
83 /**
84 * Checks the Length. If the current TLV length is above the expected length of the
85 * PDU, an exception is thrown.
86 *
87 * The current Object contains the sum of all included Objects and element, which is
88 * compared with the PDU's expected length (the Length part of the PDU containing the Object).
89 *
90 * @param object The Object that is being decoded.
91 * @param tlv The current TLV
92 * @throws DecoderException Thrown if the expected length is lower than the sum
93 * of all the included elements.
94 */
95 protected void checkLength( Asn1Object object, TLV tlv ) throws DecoderException
96 {
97
98 // Create a new expected Length
99 int expectedLength = tlv.getLength().getLength();
100
101 int tlvLength = tlv.getSize();
102
103 if ( DEBUG )
104 {
105 log.debug(
106 "Expected Length = " + ( ( Asn1Object ) object ).getExpectedLength() +
107 ", current length = " + ( ( Asn1Object ) object ).getCurrentLength() +
108 ", added length = " + expectedLength +
109 ", tlv length = " + tlvLength );
110 }
111
112 // We already are at the top level.
113 // An exception will be thrown if the current length exceed the expected length
114 ( ( Asn1Object ) object ).addLength( tlvLength );
115 }
116
117 /**
118 * Get the transition associated with the state and tag
119 * @param state The current state
120 * @param tag The current tag
121 * @return A valid transition if any, or null.
122 */
123 public GrammarTransition getTransition( int state, int tag )
124 {
125 return transitions[state][tag & IStates.STATES_SWITCH_MASK];
126 }
127
128 /**
129 * The main function. This is where an action is executed. If the
130 * action is null, nothing is done.
131 *
132 * @param container The Asn1Container
133 *
134 * @throws DecoderException Thrown if anything went wrong
135 */
136 public void executeAction( IAsn1Container container ) throws DecoderException
137 {
138
139 int currentState = container.getTransition();
140 IGrammar currentGrammar = container.getGrammar();
141
142 // We have to deal with the special case of a GRAMMAR_END state
143 if ( currentState == IStates.END_STATE )
144 {
145 currentState = container.restoreGrammar();
146
147 if ( currentState == IStates.END_STATE )
148 {
149 return;
150 }
151 }
152
153 Tag tag = container.getCurrentTLV().getTag();
154 byte tagByte = tag.getTagByte();
155
156 // We will loop until no more actions are to be executed
157 while ( true )
158 {
159
160 GrammarTransition transition = ( ( AbstractGrammar ) container.getGrammar() )
161 .getTransition( currentState, tagByte & IStates.STATES_SWITCH_MASK );
162
163 if ( transition == null )
164 {
165
166 if ( container.getCurrentGrammar() == 0 )
167 {
168 String errorMessage = "Bad transition from state " +
169 currentGrammar.getStatesEnum().getState( container.getCurrentGrammarType(),
170 currentState ) + ", tag " + StringUtils.dumpByte( tag.getTagByte() );
171
172 log.error( errorMessage );
173
174 // If we have no more grammar on the stack, then this is an error
175 throw new DecoderException( "Bad transition !" );
176 }
177 else
178 {
179
180 // We have finished with the current grammar, so we have to continue with the
181 // previous one.
182 currentState = container.restoreGrammar();
183 continue;
184 }
185 }
186
187 if ( DEBUG )
188 {
189 log.debug( transition.toString( container.getCurrentGrammarType(),
190 currentGrammar.getStatesEnum() ) );
191 }
192
193 int nextState = transition.getNextState();
194
195 if ( ( ( nextState & IStates.GRAMMAR_SWITCH_MASK ) != 0 ) &&
196 ( nextState != IStates.END_STATE ) )
197 {
198
199 if ( DEBUG )
200 {
201 log.debug(
202 "Switching from grammar " +
203 container.getStates().getGrammarName( currentGrammar ) +
204 " to grammar " + container.getStates().getGrammarName( ( nextState >> 8 ) - 1 ) );
205 }
206
207 // We have a grammar switch, so we change the current state to the initial
208 // state in the new grammar and loop.
209 container.switchGrammar( currentState, nextState & IStates.GRAMMAR_SWITCH_MASK );
210 currentState = IStates.INIT_GRAMMAR_STATE;
211 }
212 else
213 {
214
215 // This is not a grammar switch, so we execute the
216 // action if we have one, and we quit the loop.
217 container.setTransition( nextState );
218
219 if ( transition.hasAction() )
220 {
221 transition.getAction().action( container );
222 }
223
224 break;
225 }
226 }
227 }
228
229 /**
230 * Get the states of the current grammar
231 *
232 * @return Returns the statesEnum.
233 */
234 public IStates getStatesEnum()
235 {
236 return statesEnum;
237 }
238
239 /**
240 * Set the states for this grammar
241 *
242 * @param statesEnum The statesEnum to set.
243 */
244 public void setStatesEnum( IStates statesEnum )
245 {
246 this.statesEnum = statesEnum;
247 }
248 }