Java tutorial
// ASM: a very small and fast Java bytecode manipulation framework // Copyright (c) 2000-2011 INRIA, France Telecom // All rights reserved. // // Redistribution and use in source and binary forms, with or without // modification, are permitted provided that the following conditions // are met: // 1. Redistributions of source code must retain the above copyright // notice, this list of conditions and the following disclaimer. // 2. Redistributions in binary form must reproduce the above copyright // notice, this list of conditions and the following disclaimer in the // documentation and/or other materials provided with the distribution. // 3. Neither the name of the copyright holders nor the names of its // contributors may be used to endorse or promote products derived from // this software without specific prior written permission. // // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" // AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE // IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE // ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE // LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR // CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF // SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS // INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN // CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) // ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF // THE POSSIBILITY OF SUCH DAMAGE. package org.objectweb.asm; /** * An entry of the constant pool, of the BootstrapMethods attribute, or of the (ASM specific) type * table of a class. * * @see <a href="https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.4">JVMS * 4.4</a> * @see <a href="https://docs.oracle.com/javase/specs/jvms/se9/html/jvms-4.html#jvms-4.7.23">JVMS * 4.7.23</a> * @author Eric Bruneton */ abstract class Symbol { // Tag values for the constant pool entries (using the same order as in the JVMS). /** The tag value of CONSTANT_Class_info JVMS structures. */ static final int CONSTANT_CLASS_TAG = 7; /** The tag value of CONSTANT_Fieldref_info JVMS structures. */ static final int CONSTANT_FIELDREF_TAG = 9; /** The tag value of CONSTANT_Methodref_info JVMS structures. */ static final int CONSTANT_METHODREF_TAG = 10; /** The tag value of CONSTANT_InterfaceMethodref_info JVMS structures. */ static final int CONSTANT_INTERFACE_METHODREF_TAG = 11; /** The tag value of CONSTANT_String_info JVMS structures. */ static final int CONSTANT_STRING_TAG = 8; /** The tag value of CONSTANT_Integer_info JVMS structures. */ static final int CONSTANT_INTEGER_TAG = 3; /** The tag value of CONSTANT_Float_info JVMS structures. */ static final int CONSTANT_FLOAT_TAG = 4; /** The tag value of CONSTANT_Long_info JVMS structures. */ static final int CONSTANT_LONG_TAG = 5; /** The tag value of CONSTANT_Double_info JVMS structures. */ static final int CONSTANT_DOUBLE_TAG = 6; /** The tag value of CONSTANT_NameAndType_info JVMS structures. */ static final int CONSTANT_NAME_AND_TYPE_TAG = 12; /** The tag value of CONSTANT_Utf8_info JVMS structures. */ static final int CONSTANT_UTF8_TAG = 1; /** The tag value of CONSTANT_MethodHandle_info JVMS structures. */ static final int CONSTANT_METHOD_HANDLE_TAG = 15; /** The tag value of CONSTANT_MethodType_info JVMS structures. */ static final int CONSTANT_METHOD_TYPE_TAG = 16; /** The tag value of CONSTANT_Dynamic_info JVMS structures. */ static final int CONSTANT_DYNAMIC_TAG = 17; /** The tag value of CONSTANT_InvokeDynamic_info JVMS structures. */ static final int CONSTANT_INVOKE_DYNAMIC_TAG = 18; /** The tag value of CONSTANT_Module_info JVMS structures. */ static final int CONSTANT_MODULE_TAG = 19; /** The tag value of CONSTANT_Package_info JVMS structures. */ static final int CONSTANT_PACKAGE_TAG = 20; // Tag values for the BootstrapMethods attribute entries (ASM specific tag). /** The tag value of the BootstrapMethods attribute entries. */ static final int BOOTSTRAP_METHOD_TAG = 64; // Tag values for the type table entries (ASM specific tags). /** The tag value of a normal type entry in the (ASM specific) type table of a class. */ static final int TYPE_TAG = 128; /** * The tag value of an {@link Frame#ITEM_UNINITIALIZED} type entry in the type table of a class. */ static final int UNINITIALIZED_TYPE_TAG = 129; /** The tag value of a merged type entry in the (ASM specific) type table of a class. */ static final int MERGED_TYPE_TAG = 130; // Instance fields. /** * The index of this symbol in the constant pool, in the BootstrapMethods attribute, or in the * (ASM specific) type table of a class (depending on the {@link #tag} value). */ final int index; /** * A tag indicating the type of this symbol. Must be one of the static tag values defined in this * class. */ final int tag; /** * The internal name of the owner class of this symbol. Only used for {@link * #CONSTANT_FIELDREF_TAG}, {@link #CONSTANT_METHODREF_TAG}, {@link * #CONSTANT_INTERFACE_METHODREF_TAG}, and {@link #CONSTANT_METHOD_HANDLE_TAG} symbols. */ final String owner; /** * The name of the class field or method corresponding to this symbol. Only used for {@link * #CONSTANT_FIELDREF_TAG}, {@link #CONSTANT_METHODREF_TAG}, {@link * #CONSTANT_INTERFACE_METHODREF_TAG}, {@link #CONSTANT_NAME_AND_TYPE_TAG}, {@link * #CONSTANT_METHOD_HANDLE_TAG}, {@link #CONSTANT_DYNAMIC_TAG} and {@link * #CONSTANT_INVOKE_DYNAMIC_TAG} symbols. */ final String name; /** * The string value of this symbol. This is: * * <ul> * <li>a field or method descriptor for {@link #CONSTANT_FIELDREF_TAG}, {@link * #CONSTANT_METHODREF_TAG}, {@link #CONSTANT_INTERFACE_METHODREF_TAG}, {@link * #CONSTANT_NAME_AND_TYPE_TAG}, {@link #CONSTANT_METHOD_HANDLE_TAG}, {@link * #CONSTANT_METHOD_TYPE_TAG}, {@link #CONSTANT_DYNAMIC_TAG} and {@link * #CONSTANT_INVOKE_DYNAMIC_TAG} symbols, * <li>an arbitrary string for {@link #CONSTANT_UTF8_TAG} and {@link #CONSTANT_STRING_TAG} * symbols, * <li>an internal class name for {@link #CONSTANT_CLASS_TAG}, {@link #TYPE_TAG} and {@link * #UNINITIALIZED_TYPE_TAG} symbols, * <li>{@literal null} for the other types of symbol. * </ul> */ final String value; /** * The numeric value of this symbol. This is: * * <ul> * <li>the symbol's value for {@link #CONSTANT_INTEGER_TAG},{@link #CONSTANT_FLOAT_TAG}, {@link * #CONSTANT_LONG_TAG}, {@link #CONSTANT_DOUBLE_TAG}, * <li>the CONSTANT_MethodHandle_info reference_kind field value for {@link * #CONSTANT_METHOD_HANDLE_TAG} symbols, * <li>the CONSTANT_InvokeDynamic_info bootstrap_method_attr_index field value for {@link * #CONSTANT_INVOKE_DYNAMIC_TAG} symbols, * <li>the offset of a bootstrap method in the BootstrapMethods boostrap_methods array, for * {@link #CONSTANT_DYNAMIC_TAG} or {@link #BOOTSTRAP_METHOD_TAG} symbols, * <li>the bytecode offset of the NEW instruction that created an {@link * Frame#ITEM_UNINITIALIZED} type for {@link #UNINITIALIZED_TYPE_TAG} symbols, * <li>the indices (in the class' type table) of two {@link #TYPE_TAG} source types for {@link * #MERGED_TYPE_TAG} symbols, * <li>0 for the other types of symbol. * </ul> */ final long data; /** * Additional information about this symbol, generally computed lazily. <i>Warning: the value of * this field is ignored when comparing Symbol instances</i> (to avoid duplicate entries in a * SymbolTable). Therefore, this field should only contain data that can be computed from the * other fields of this class. It contains: * * <ul> * <li>the {@link Type#getArgumentsAndReturnSizes} of the symbol's method descriptor for {@link * #CONSTANT_METHODREF_TAG}, {@link #CONSTANT_INTERFACE_METHODREF_TAG} and {@link * #CONSTANT_INVOKE_DYNAMIC_TAG} symbols, * <li>the index in the InnerClasses_attribute 'classes' array (plus one) corresponding to this * class, for {@link #CONSTANT_CLASS_TAG} symbols, * <li>the index (in the class' type table) of the merged type of the two source types for * {@link #MERGED_TYPE_TAG} symbols, * <li>0 for the other types of symbol, or if this field has not been computed yet. * </ul> */ int info; /** * Constructs a new Symbol. This constructor can't be used directly because the Symbol class is * abstract. Instead, use the factory methods of the {@link SymbolTable} class. * * @param index the symbol index in the constant pool, in the BootstrapMethods attribute, or in * the (ASM specific) type table of a class (depending on 'tag'). * @param tag the symbol type. Must be one of the static tag values defined in this class. * @param owner The internal name of the symbol's owner class. Maybe {@literal null}. * @param name The name of the symbol's corresponding class field or method. Maybe {@literal * null}. * @param value The string value of this symbol. Maybe {@literal null}. * @param data The numeric value of this symbol. */ Symbol(final int index, final int tag, final String owner, final String name, final String value, final long data) { this.index = index; this.tag = tag; this.owner = owner; this.name = name; this.value = value; this.data = data; } /** * Returns the result {@link Type#getArgumentsAndReturnSizes} on {@link #value}. * * @return the result {@link Type#getArgumentsAndReturnSizes} on {@link #value} (memoized in * {@link #info} for efficiency). This should only be used for {@link * #CONSTANT_METHODREF_TAG}, {@link #CONSTANT_INTERFACE_METHODREF_TAG} and {@link * #CONSTANT_INVOKE_DYNAMIC_TAG} symbols. */ int getArgumentsAndReturnSizes() { if (info == 0) { info = Type.getArgumentsAndReturnSizes(value); } return info; } }