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.Objects;
29 import java.util.function.BiFunction;
30
31 /**
32 * An operation transformer.
33 */
34 @FunctionalInterface
35 public interface OpTransformer extends BiFunction<Block.Builder, Op, Block.Builder> {
36 /**
37 * A copying transformer that applies the operation to the block builder, and returning the block builder.
38 */
39 OpTransformer COPYING_TRANSFORMER = (block, op) -> {
40 block.op(op);
41 return block;
42 };
43
44 /**
45 * A transformer that performs no action on the block builder.
46 */
47 OpTransformer NOOP_TRANSFORMER = (block, op) -> block;
48
49 /**
50 * A transformer that drops location information from operations.
51 */
52 OpTransformer DROP_LOCATION_TRANSFORMER = (block, op) -> {
53 Op.Result r = block.op(op);
54 r.op().setLocation(Location.NO_LOCATION);
55 return block;
56 };
57
58 /**
59 * A transformer that lowers operations that are {@link Op.Lowerable lowerable},
60 * and copies other operations.
61 */
62 OpTransformer LOWERING_TRANSFORMER = (block, op) -> {
63 if (op instanceof Op.Lowerable lop) {
64 return lop.lower(block);
65 } else {
66 block.op(op);
67 return block;
68 }
69 };
70
71 /**
72 * Transforms a given operation to zero or more other operations appended to the
73 * given block builder. Returns a block builder to be used for appending further operations, such
74 * as subsequent operations from the same block as the given operation.
75 *
76 * @param block the block builder.
77 * @param op the operation to transform.
78 * @return the block builder to append to for subsequent operations to transform that have same parent block.
79 */
80 Block.Builder apply(Block.Builder block, Op op);
81
82 /**
83 * Transforms a given block to zero or more operations appended to the given block builder.
84 *
85 * @implSpec
86 * The default implementation iterates through each operation of the block to transform
87 * and {@link #apply(Block.Builder, Op) applies} a block builder and the operation to this
88 * transformer.
89 * On first iteration the block builder that is applied is block builder passed as an argument
90 * to this method.
91 * On second and subsequent iterations the block builder that is applied is the resulting
92 * block builder of the prior iteration.
93 *
94 * @param block the block builder
95 * @param b the block to transform
96 * @throws NullPointerException if a resulting block builder is null
97 */
98 default void apply(Block.Builder block, Block b) {
99 for (Op op : b.ops()) {
100 block = apply(block, op);
101 // @@@ See andThen composition
102 Objects.requireNonNull(block);
103 }
104 }
105
106 default OpTransformer compose(OpTransformer before) {
107 return before.andThen(this);
108 }
109
110 default OpTransformer andThen(OpTransformer after) {
111 if (after == NOOP_TRANSFORMER) {
112 return this;
113 } else if (this == NOOP_TRANSFORMER) {
114 return after;
115 } else {
116 return (bb, o) -> {
117 Block.Builder nbb = apply(bb, o);
118 if (nbb != null) {
119 return after.apply(nbb, o);
120 } else {
121 // @@@ This does not currently occur
122 return null;
123 }
124 };
125 }
126 }
127 }