1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * http://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17 package org.apache.commons.jexl3.internal;
18
19 import java.util.ArrayDeque;
20 import java.util.Deque;
21
22 /**
23 * The set of valued symbols defined in a lexical frame.
24 * <p>The symbol identifiers are determined by the functional scope.
25 */
26 public class LexicalFrame extends LexicalScope {
27 /**
28 * The script frame.
29 */
30 private final Frame frame;
31 /**
32 * Previous frame.
33 */
34 protected final LexicalFrame previous;
35 /**
36 * The stack of values in the lexical frame.
37 */
38 private Deque<Object> stack;
39
40 /**
41 * Lexical frame ctor.
42 *
43 * @param scriptf the script frame
44 * @param outerf the previous lexical frame
45 */
46 public LexicalFrame(final Frame scriptf, final LexicalFrame outerf) {
47 this.previous = outerf;
48 this.frame = scriptf;
49 }
50
51 /**
52 * Copy ctor.
53 *
54 * @param src the frame to copy
55 */
56 public LexicalFrame(final LexicalFrame src) {
57 super(src);
58 frame = src.frame;
59 previous = src.previous;
60 stack = src.stack != null ? new ArrayDeque<>(src.stack) : null;
61 }
62
63 /**
64 * Define the arguments.
65 *
66 * @return this frame
67 */
68 public LexicalFrame defineArgs() {
69 if (frame != null) {
70 final int argc = frame.getScope().getArgCount();
71 for (int a = 0; a < argc; ++a) {
72 super.addSymbol(a);
73 }
74 }
75 return this;
76 }
77
78 /**
79 * Defines a symbol.
80 *
81 * @param symbol the symbol to define
82 * @param capture whether this redefines a captured symbol
83 * @return true if symbol is defined, false otherwise
84 */
85 public boolean defineSymbol(final int symbol, final boolean capture) {
86 final boolean declared = addSymbol(symbol);
87 if (declared && capture) {
88 if (stack == null) {
89 stack = new ArrayDeque<>();
90 }
91 stack.push(symbol);
92 Object value = frame.get(symbol);
93 if (value == null) {
94 value = this;
95 }
96 stack.push(value);
97 }
98 return declared;
99 }
100
101 /**
102 * Pops back values and lexical frame.
103 *
104 * @return the previous frame
105 */
106 public LexicalFrame pop() {
107 // undefine all symbols
108 clearSymbols(s -> frame.set(s, Scope.UNDEFINED) );
109 // restore values of captured symbols that were overwritten
110 if (stack != null) {
111 while (!stack.isEmpty()) {
112 Object value = stack.pop();
113 if (value == Scope.UNDECLARED) {
114 value = Scope.UNDEFINED;
115 } else if (value == this) {
116 value = null;
117 }
118 final int symbol = (Integer) stack.pop();
119 frame.set(symbol, value);
120 }
121 }
122 return previous;
123 }
124
125 }