8308753: Class-File API transition to Preview

Reviewed-by: ihse, mchung, vromero

src/java.base/share/classes/java/lang/classfile/components/CodeStackTracker.java

@@ -0,0 +1,90 @@
+/*
+ * Copyright (c) 2022, 2023, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package java.lang.classfile.components;
+
+import java.util.Collection;
+import java.util.Optional;
+import java.lang.classfile.CodeTransform;
+import java.lang.classfile.Label;
+import java.lang.classfile.TypeKind;
+import jdk.internal.classfile.impl.CodeStackTrackerImpl;
+import jdk.internal.javac.PreviewFeature;
+
+/**
+ * {@link CodeStackTracker} is a {@link CodeTransform} tracking stack content
+ * and calculating max stack size.
+ * <p>
+ * Sample use:
+ * <p>
+ * {@snippet lang=java :
+ *     var stackTracker = CodeStackTracker.of();
+ *     codeBuilder.transforming(stackTracker, trackedBuilder -> {
+ *         trackedBuilder.aload(0);
+ *         trackedBuilder.lconst_0();
+ *         trackedBuilder.ifThen(...);
+ *         ...
+ *         var stack = stackTracker.stack().get();
+ *         int maxStack = stackTracker.maxStackSize().get();
+ *     });
+ * }
+ *
+ * @since 22
+ */
+@PreviewFeature(feature = PreviewFeature.Feature.CLASSFILE_API)
+public sealed interface CodeStackTracker extends CodeTransform permits CodeStackTrackerImpl {
+
+    /**
+     * Creates new instance of {@link CodeStackTracker} initialized with provided stack items.
+     * @param initialStack initial stack content
+     * @return new instance of {@link CodeStackTracker}
+     */
+    static CodeStackTracker of(TypeKind... initialStack) {
+        return new CodeStackTrackerImpl(initialStack);
+    }
+
+    /**
+      * Returns {@linkplain Collection} of {@linkplain TypeKind} representing current stack.
+      * Returns an empty {@linkplain Optional} when the Stack content is unknown
+      * (right after {@code xRETURN, ATHROW, GOTO, GOTO_W, LOOKUPSWITCH, TABLESWITCH} instructions).
+      * <p>
+      * Temporary unknown stack content can be recovered by binding of a {@linkplain Label} used as
+      * target of a branch instruction from existing code with known stack (forward branch target),
+      * or by binding of a {@linkplain Label} defining an exception handler (exception handler code start).
+      *
+      * @return actual stack content, or an empty {@linkplain Optional} if unknown
+      */
+    Optional<Collection<TypeKind>> stack();
+
+    /**
+      * Returns tracked max stack size.
+      * Returns an empty {@linkplain Optional} when max stack size tracking has been lost.
+      * <p>
+      * Max stack size tracking is permanently lost when a stack instruction appears
+      * and the actual stack content is unknown.
+      *
+      * @return tracked max stack size, or an empty {@linkplain Optional} if tracking has been lost
+      */
+    Optional<Integer> maxStackSize();
+}