8308753: Class-File API transition to Preview

Reviewed-by: ihse, mchung, vromero

src/java.base/share/classes/java/lang/classfile/attribute/SignatureAttribute.java

@@ -0,0 +1,122 @@
+/*
+ * Copyright (c) 2022, 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.attribute;
+
+import java.lang.classfile.Attribute;
+import java.lang.classfile.ClassElement;
+import java.lang.classfile.ClassSignature;
+import java.lang.classfile.FieldElement;
+import java.lang.classfile.MethodElement;
+import java.lang.classfile.constantpool.Utf8Entry;
+import jdk.internal.classfile.impl.BoundAttribute;
+import java.lang.classfile.MethodSignature;
+import java.lang.classfile.Signature;
+import jdk.internal.classfile.impl.TemporaryConstantPool;
+import jdk.internal.classfile.impl.UnboundAttribute;
+import jdk.internal.javac.PreviewFeature;
+
+/**
+ * Models the {@code Signature} attribute {@jvms 4.7.9}, which
+ * can appear on classes, methods, or fields. Delivered as a
+ * {@link java.lang.classfile.ClassElement}, {@link java.lang.classfile.FieldElement}, or
+ * {@link java.lang.classfile.MethodElement} when traversing
+ * the corresponding model type.
+ * <p>
+ * The attribute does not permit multiple instances in a given location.
+ * Subsequent occurrence of the attribute takes precedence during the attributed
+ * element build or transformation.
+ * <p>
+ * The attribute was introduced in the Java SE Platform version 5.0.
+ *
+ * @since 22
+ */
+@PreviewFeature(feature = PreviewFeature.Feature.CLASSFILE_API)
+public sealed interface SignatureAttribute
+        extends Attribute<SignatureAttribute>,
+                ClassElement, MethodElement, FieldElement
+        permits BoundAttribute.BoundSignatureAttribute, UnboundAttribute.UnboundSignatureAttribute {
+
+    /**
+     * {@return the signature for the class, method, or field}
+     */
+    Utf8Entry signature();
+
+    /**
+     * Parse the signature as a class signature.
+     * @return the class signature
+     */
+    default ClassSignature asClassSignature() {
+        return ClassSignature.parseFrom(signature().stringValue());
+    }
+
+    /**
+     * Parse the signature as a method signature.
+     * @return the method signature
+     */
+    default MethodSignature asMethodSignature() {
+        return MethodSignature.parseFrom(signature().stringValue());
+    }
+
+    /**
+     * Parse the signature as a type signature.
+     * @return the type signature
+     */
+    default Signature asTypeSignature() {
+        return Signature.parseFrom(signature().stringValue());
+    }
+
+    /**
+     * {@return a {@code Signature} attribute for a class}
+     * @param classSignature the signature
+     */
+    static SignatureAttribute of(ClassSignature classSignature) {
+        return of(TemporaryConstantPool.INSTANCE.utf8Entry(classSignature.signatureString()));
+    }
+
+    /**
+     * {@return a {@code Signature} attribute for a method}
+     * @param methodSignature the signature
+     */
+    static SignatureAttribute of(MethodSignature methodSignature) {
+        return of(TemporaryConstantPool.INSTANCE.utf8Entry(methodSignature.signatureString()));
+    }
+
+    /**
+     * {@return a {@code Signature} attribute}
+     * @param signature the signature
+     */
+    static SignatureAttribute of(Signature signature) {
+        return of(TemporaryConstantPool.INSTANCE.utf8Entry(signature.signatureString()));
+    }
+
+    /**
+     * {@return a {@code Signature} attribute}
+     * @param signature the signature
+     */
+    static SignatureAttribute of(Utf8Entry signature) {
+        return new UnboundAttribute.UnboundSignatureAttribute(signature);
+    }
+}