init

2024-11-30 19:03:49 +08:00
commit 1e6763c160
3806 changed files with 737676 additions and 0 deletions
--- a/java/org/apache/tomcat/util/bcel/classfile/Constant.java
+++ b/java/org/apache/tomcat/util/bcel/classfile/Constant.java
@@ -0,0 +1,108 @@
+/*
+ *  Licensed to the Apache Software Foundation (ASF) under one or more
+ *  contributor license agreements.  See the NOTICE file distributed with
+ *  this work for additional information regarding copyright ownership.
+ *  The ASF licenses this file to You under the Apache License, Version 2.0
+ *  (the "License"); you may not use this file except in compliance with
+ *  the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ */
+package org.apache.tomcat.util.bcel.classfile;
+
+import java.io.DataInput;
+import java.io.IOException;
+
+import org.apache.tomcat.util.bcel.Const;
+
+/**
+ * Abstract superclass for classes to represent the different constant types
+ * in the constant pool of a class file. The classes keep closely to
+ * the JVM specification.
+ *
+ * @author  <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
+ */
+public abstract class Constant {
+
+    /* In fact this tag is redundant since we can distinguish different
+     * `Constant' objects by their type, i.e., via `instanceof'. In some
+     * places we will use the tag for switch()es anyway.
+     *
+     * First, we want match the specification as closely as possible. Second we
+     * need the tag as an index to select the corresponding class name from the
+     * `CONSTANT_NAMES' array.
+     */
+    protected final byte tag;
+
+    Constant(final byte tag) {
+        this.tag = tag;
+    }
+
+    /**
+     * @return Tag of constant, i.e., its type. No setTag() method to avoid
+     * confusion.
+     */
+    public final byte getTag() {
+        return tag;
+    }
+
+    /**
+     * Read one constant from the given input, the type depends on a tag byte.
+     *
+     * @param dataInput Input stream
+     * @return Constant object
+     * @throws IOException if an I/O error occurs reading from the given {@code dataInput}.
+     * @throws ClassFormatException if the next byte is not recognized
+     */
+    static Constant readConstant(final DataInput dataInput) throws IOException, ClassFormatException {
+        final byte b = dataInput.readByte(); // Read tag byte
+        int skipSize;
+        switch (b) {
+            case Const.CONSTANT_Class:
+                return new ConstantClass(dataInput);
+            case Const.CONSTANT_Integer:
+                return new ConstantInteger(dataInput);
+            case Const.CONSTANT_Float:
+                return new ConstantFloat(dataInput);
+            case Const.CONSTANT_Long:
+                return new ConstantLong(dataInput);
+            case Const.CONSTANT_Double:
+                return new ConstantDouble(dataInput);
+            case Const.CONSTANT_Utf8:
+                return ConstantUtf8.getInstance(dataInput);
+            case Const.CONSTANT_String:
+            case Const.CONSTANT_MethodType:
+            case Const.CONSTANT_Module:
+            case Const.CONSTANT_Package:
+                skipSize = 2; // unsigned short
+                break;
+            case Const.CONSTANT_MethodHandle:
+                skipSize = 3; // unsigned byte, unsigned short
+                break;
+            case Const.CONSTANT_Fieldref:
+            case Const.CONSTANT_Methodref:
+            case Const.CONSTANT_InterfaceMethodref:
+            case Const.CONSTANT_NameAndType:
+            case Const.CONSTANT_Dynamic:
+            case Const.CONSTANT_InvokeDynamic:
+                skipSize = 4; // unsigned short, unsigned short
+                break;
+            default:
+                throw new ClassFormatException("Invalid byte tag in constant pool: " + b);
+        }
+        Utility.skipFully(dataInput, skipSize);
+        return null;
+    }
+
+    @Override
+    public String toString() {
+        return "[" + tag + "]";
+    }
+}