1 /*
2 * Copyright (c) 2024, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26 package java.lang.reflect.code;
27
28 import java.util.List;
29 import java.util.function.BiFunction;
30 import java.util.function.Predicate;
31 import java.util.stream.Stream;
32
33 /**
34 * A code element, one of {@link Body body}, {@link Block block}, or {@link Op operation}.
35 * <p>
36 * A code element may have child code elements, and so on, to form a tree. A (root) code element and all its descendants
37 * can be traversed.
38 *
39 * @param <E> the code element type
40 * @param <C> the child code element type.
41 * @sealedGraph
42 */
43 // @@@ E may not be needed
44 public sealed interface CodeElement<
45 E extends CodeElement<E, C>,
46 C extends CodeElement<C, ?>>
47 extends CodeItem
48 permits Body, Block, Op {
49
50 /**
51 * {@return a stream of code elements sorted topologically in pre-order traversal.}
52 */
53 // Code copied into the compiler cannot depend on new gatherer API
54 default Stream<CodeElement<?, ?>> elements() {
55 /*__throw new UnsupportedOperationException();__*/ return Stream.of(Void.class).gather(() -> (_, _, downstream) -> traversePreOrder(downstream::push));
56 }
57
58 // private boolean traversePreOrder(Gatherer.Downstream<? super CodeElement<?, ?>> v) {
59 private boolean traversePreOrder(Predicate<? super CodeElement<?, ?>> v) {
60 if (!v.test(this)) {
61 return false;
62 }
63 for (C c : children()) {
64 if (!((CodeElement<?, ?>) c).traversePreOrder(v)) {
65 return false;
66 }
67 }
68 return true;
69 }
70
71 /**
72 * Traverses this code element and any descendant code elements.
73 * <p>
74 * Traversal is performed in pre-order, reporting each code element to the visitor.
75 *
76 * @param t the traversing accumulator
77 * @param v the code element visitor
78 * @param <T> accumulator type
79 * @return the traversing accumulator
80 */
81 default <T> T traverse(T t, BiFunction<T, CodeElement<?, ?>, T> v) {
82 t = v.apply(t, this);
83 for (C r : children()) {
84 t = r.traverse(t, v);
85 }
86
87 return t;
88 }
89
90 /**
91 * Creates a visiting function for bodies.
92 *
93 * @param v the body visitor
94 * @param <T> accumulator type
95 * @return the visiting function for bodies
96 */
97 static <T> BiFunction<T, CodeElement<?, ?>, T> bodyVisitor(BiFunction<T, Body, T> v) {
98 return (t, e) -> e instanceof Body f
99 ? v.apply(t, f)
100 : t;
101 }
102
103 /**
104 * Creates a visiting function for blocks.
105 *
106 * @param v the block visitor
107 * @param <T> accumulator type
108 * @return the visiting function for blocks
109 */
110 static <T> BiFunction<T, CodeElement<?, ?>, T> blockVisitor(BiFunction<T, Block, T> v) {
111 return (t, e) -> e instanceof Block f
112 ? v.apply(t, f)
113 : t;
114 }
115
116 /**
117 * Creates a visiting function for operations.
118 *
119 * @param v the operation visitor
120 * @param <T> accumulator type
121 * @return the visiting function for operations
122 */
123 static <T> BiFunction<T, CodeElement<?, ?>, T> opVisitor(BiFunction<T, Op, T> v) {
124 return (t, e) -> e instanceof Op f
125 ? v.apply(t, f)
126 : t;
127 }
128
129 /**
130 * Returns the parent code element.
131 * <p>
132 * If this element is an instance of {@code Op} then the parent may be {@code null}
133 * if operation is not assigned to a block.
134 *
135 * @return the parent code element
136 */
137 CodeElement<?, E> parent();
138
139 /**
140 * Returns the child code elements, as an unmodifiable list.
141 *
142 * @return the child code elements
143 */
144 List<C> children();
145 }