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.Arrays;
20
21 /**
22 * A call frame, created from a scope, stores the arguments and local variables in a "stack frame" (sic).
23 * @since 3.0
24 */
25 public final class Frame {
26 /** The scope. */
27 private final Scope scope;
28 /** The actual stack frame. */
29 private final Object[] stack;
30 /** Number of curried parameters. */
31 private final int curried;
32
33 /**
34 * Creates a new frame.
35 * @param s the scope
36 * @param r the stack frame
37 * @param c the number of curried parameters
38 */
39 Frame(final Scope s, final Object[] r, final int c) {
40 scope = s;
41 stack = r;
42 curried = c;
43 }
44
45 /**
46 * Assign values to this frame.
47 * @param values the values
48 * @return this frame
49 */
50 Frame assign(final Object... values) {
51 if (stack != null) {
52 final int nparm = scope.getArgCount();
53 final Object[] copy = stack.clone();
54 int ncopy = 0;
55 if (values != null && values.length > 0) {
56 ncopy = Math.min(nparm - curried, Math.min(nparm, values.length));
57 System.arraycopy(values, 0, copy, curried, ncopy);
58 }
59 // unbound parameters are defined as null
60 Arrays.fill(copy, curried + ncopy, nparm, null);
61 return new Frame(scope, copy, curried + ncopy);
62 }
63 return this;
64 }
65
66 /**
67 * Gets a value.
68 * @param s the offset in this frame
69 * @return the stacked value
70 */
71 Object get(final int s) {
72 return stack[s];
73 }
74
75 /**
76 * Gets the scope.
77 * @return this frame scope
78 */
79 public Scope getScope() {
80 return scope;
81 }
82
83 /**
84 * Gets this script unbound parameters, i.e. parameters not bound through curry().
85 * @return the parameter names
86 */
87 public String[] getUnboundParameters() {
88 return scope.getParameters(curried);
89 }
90
91 /**
92 * Whether this frame defines a symbol, ie declared it and assigned it a value.
93 * @param s the offset in this frame
94 * @return true if this symbol has been assigned a value, false otherwise
95 */
96 boolean has(final int s) {
97 return s >= 0 && s < stack.length && stack[s] != Scope.UNDECLARED;
98 }
99
100 /**
101 * Replace any instance of a closure in this stack by its (fuzzy encoded) offset in it.
102 * <p>This is to avoid the cyclic dependency between the closure and its frame stack that
103 * may point back to it that occur with recursive function definitions.</p>
104 * @param closure the owning closure
105 * @return the cleaned-up stack or the stack itself (most of the time)
106 */
107 Object[] nocycleStack(final Closure closure) {
108 Object[] ns = stack;
109 for(int i = 0; i < stack.length; ++i) {
110 if (stack[i] == closure) {
111 if (ns == stack) {
112 ns = stack.clone();
113 }
114 // fuzz it a little
115 ns[i] = Closure.class.hashCode() + i;
116 }
117 }
118 return ns;
119 }
120
121 /**
122 * Sets a value.
123 * @param r the offset in this frame
124 * @param value the value to set in this frame
125 */
126 void set(final int r, final Object value) {
127 stack[r] = value;
128 }
129
130 }