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89 lines
3.6 KiB
Java
89 lines
3.6 KiB
Java
/*
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* Copyright (c) 2022, 2024, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation. Oracle designates this
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* particular file as subject to the "Classpath" exception as provided
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* by Oracle in the LICENSE file that accompanied this code.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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package java.lang.classfile.components;
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import java.lang.classfile.CodeTransform;
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import java.lang.classfile.Label;
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import java.lang.classfile.TypeKind;
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import java.util.Collection;
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import java.util.Optional;
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import jdk.internal.classfile.impl.CodeStackTrackerImpl;
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/**
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* {@link CodeStackTracker} is a {@link CodeTransform} tracking stack content
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* and calculating max stack size.
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* <p>
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* Sample use:
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*
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* {@snippet lang=java :
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* var stackTracker = CodeStackTracker.of();
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* codeBuilder.transforming(stackTracker, trackedBuilder -> {
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* trackedBuilder.aload(0);
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* trackedBuilder.lconst_0();
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* trackedBuilder.ifThen(...);
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* ...
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* var stack = stackTracker.stack().get();
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* int maxStack = stackTracker.maxStackSize().get();
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* });
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* }
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*
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* @since 24
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*/
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public sealed interface CodeStackTracker extends CodeTransform permits CodeStackTrackerImpl {
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/**
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* Creates new instance of {@link CodeStackTracker} initialized with provided stack items.
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* @param initialStack initial stack content
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* @return new instance of {@link CodeStackTracker}
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*/
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static CodeStackTracker of(TypeKind... initialStack) {
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return new CodeStackTrackerImpl(initialStack);
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}
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/**
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* Returns {@linkplain Collection} of {@linkplain TypeKind} representing current stack.
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* Returns an empty {@linkplain Optional} when the Stack content is unknown
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* (right after {@code xRETURN, ATHROW, GOTO, GOTO_W, LOOKUPSWITCH, TABLESWITCH} instructions).
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* <p>
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* Temporary unknown stack content can be recovered by binding of a {@linkplain Label} used as
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* target of a branch instruction from existing code with known stack (forward branch target),
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* or by binding of a {@linkplain Label} defining an exception handler (exception handler code start).
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*
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* @return actual stack content, or an empty {@linkplain Optional} if unknown
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*/
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Optional<Collection<TypeKind>> stack();
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/**
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* Returns tracked max stack size.
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* Returns an empty {@linkplain Optional} when max stack size tracking has been lost.
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* <p>
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* Max stack size tracking is permanently lost when a stack instruction appears
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* and the actual stack content is unknown.
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*
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* @return tracked max stack size, or an empty {@linkplain Optional} if tracking has been lost
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*/
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Optional<Integer> maxStackSize();
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}
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