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.tree.analysis; import java.util.List; import org.objectweb.asm.Type; import org.objectweb.asm.tree.AbstractInsnNode; import org.objectweb.asm.tree.TryCatchBlockNode; /** * A semantic bytecode interpreter. More precisely, this interpreter only manages the computation of * values from other values: it does not manage the transfer of values to or from the stack, and to * or from the local variables. This separation allows a generic bytecode {@link Analyzer} to work * with various semantic interpreters, without needing to duplicate the code to simulate the * transfer of values. * * @param <V> type of the Value used for the analysis. * @author Eric Bruneton */ public abstract class Interpreter<V extends Value> { /** * The ASM API version supported by this interpreter. The value of this field must be one of * {@link org.objectweb.asm.Opcodes#ASM4}, {@link org.objectweb.asm.Opcodes#ASM5}, {@link * org.objectweb.asm.Opcodes#ASM6} or {@link org.objectweb.asm.Opcodes#ASM7}. */ protected final int api; /** * Constructs a new {@link Interpreter}. * * @param api the ASM API version supported by this interpreter. Must be one of {@link * org.objectweb.asm.Opcodes#ASM4}, {@link org.objectweb.asm.Opcodes#ASM5}, {@link * org.objectweb.asm.Opcodes#ASM6} or {@link org.objectweb.asm.Opcodes#ASM7}. */ protected Interpreter(final int api) { this.api = api; } /** * Creates a new value that represents the given type. * * <p>Called for method parameters (including <code>this</code>), exception handler variable and * with <code>null</code> type for variables reserved by long and double types. * * <p>An interpreter may choose to implement one or more of {@link * Interpreter#newReturnTypeValue(Type)}, {@link Interpreter#newParameterValue(boolean, int, * Type)}, {@link Interpreter#newEmptyValue(int)}, {@link * Interpreter#newExceptionValue(TryCatchBlockNode, Frame, Type)} to distinguish different types * of new value. * * @param type a primitive or reference type, or {@literal null} to represent an uninitialized * value. * @return a value that represents the given type. The size of the returned value must be equal to * the size of the given type. */ public abstract V newValue(Type type); /** * Creates a new value that represents the given parameter type. This method is called to * initialize the value of a local corresponding to a method parameter in a frame. * * <p>By default, calls <code>newValue(type)</code>. * * @param isInstanceMethod {@literal true} if the method is non-static. * @param local the local variable index. * @param type a primitive or reference type. * @return a value that represents the given type. The size of the returned value must be equal to * the size of the given type. */ public V newParameterValue(final boolean isInstanceMethod, final int local, final Type type) { return newValue(type); } /** * Creates a new value that represents the given return type. This method is called to initialize * the return type value of a frame. * * <p>By default, calls <code>newValue(type)</code>. * * @param type a primitive or reference type. * @return a value that represents the given type. The size of the returned value must be equal to * the size of the given type. */ public V newReturnTypeValue(final Type type) { return newValue(type); } /** * Creates a new uninitialized value for a local variable. This method is called to initialize the * value of a local that does not correspond to a method parameter, and to reset one half of a * size-2 value when the other half is assigned a size-1 value. * * <p>By default, calls <code>newValue(null)</code>. * * @param local the local variable index. * @return a value representing an uninitialized value. The size of the returned value must be * equal to 1. */ public V newEmptyValue(final int local) { return newValue(null); } /** * Creates a new value that represents the given exception type. This method is called to * initialize the exception value on the call stack at the entry of an exception handler. * * <p>By default, calls <code>newValue(exceptionType)</code>. * * @param tryCatchBlockNode the exception handler. * @param handlerFrame the exception handler frame. * @param exceptionType the exception type handled by this handler. * @return a value that represents the given {@code exceptionType}. The size of the returned value * must be equal to 1. */ public V newExceptionValue(final TryCatchBlockNode tryCatchBlockNode, final Frame<V> handlerFrame, final Type exceptionType) { return newValue(exceptionType); } /** * Interprets a bytecode instruction without arguments. This method is called for the following * opcodes: * * <p>ACONST_NULL, ICONST_M1, ICONST_0, ICONST_1, ICONST_2, ICONST_3, ICONST_4, ICONST_5, * LCONST_0, LCONST_1, FCONST_0, FCONST_1, FCONST_2, DCONST_0, DCONST_1, BIPUSH, SIPUSH, LDC, JSR, * GETSTATIC, NEW * * @param insn the bytecode instruction to be interpreted. * @return the result of the interpretation of the given instruction. * @throws AnalyzerException if an error occurred during the interpretation. */ public abstract V newOperation(AbstractInsnNode insn) throws AnalyzerException; /** * Interprets a bytecode instruction that moves a value on the stack or to or from local * variables. This method is called for the following opcodes: * * <p>ILOAD, LLOAD, FLOAD, DLOAD, ALOAD, ISTORE, LSTORE, FSTORE, DSTORE, ASTORE, DUP, DUP_X1, * DUP_X2, DUP2, DUP2_X1, DUP2_X2, SWAP * * @param insn the bytecode instruction to be interpreted. * @param value the value that must be moved by the instruction. * @return the result of the interpretation of the given instruction. The returned value must be * {@code equal} to the given value. * @throws AnalyzerException if an error occurred during the interpretation. */ public abstract V copyOperation(AbstractInsnNode insn, V value) throws AnalyzerException; /** * Interprets a bytecode instruction with a single argument. This method is called for the * following opcodes: * * <p>INEG, LNEG, FNEG, DNEG, IINC, I2L, I2F, I2D, L2I, L2F, L2D, F2I, F2L, F2D, D2I, D2L, D2F, * I2B, I2C, I2S, IFEQ, IFNE, IFLT, IFGE, IFGT, IFLE, TABLESWITCH, LOOKUPSWITCH, IRETURN, LRETURN, * FRETURN, DRETURN, ARETURN, PUTSTATIC, GETFIELD, NEWARRAY, ANEWARRAY, ARRAYLENGTH, ATHROW, * CHECKCAST, INSTANCEOF, MONITORENTER, MONITOREXIT, IFNULL, IFNONNULL * * @param insn the bytecode instruction to be interpreted. * @param value the argument of the instruction to be interpreted. * @return the result of the interpretation of the given instruction. * @throws AnalyzerException if an error occurred during the interpretation. */ public abstract V unaryOperation(AbstractInsnNode insn, V value) throws AnalyzerException; /** * Interprets a bytecode instruction with two arguments. This method is called for the following * opcodes: * * <p>IALOAD, LALOAD, FALOAD, DALOAD, AALOAD, BALOAD, CALOAD, SALOAD, IADD, LADD, FADD, DADD, * ISUB, LSUB, FSUB, DSUB, IMUL, LMUL, FMUL, DMUL, IDIV, LDIV, FDIV, DDIV, IREM, LREM, FREM, DREM, * ISHL, LSHL, ISHR, LSHR, IUSHR, LUSHR, IAND, LAND, IOR, LOR, IXOR, LXOR, LCMP, FCMPL, FCMPG, * DCMPL, DCMPG, IF_ICMPEQ, IF_ICMPNE, IF_ICMPLT, IF_ICMPGE, IF_ICMPGT, IF_ICMPLE, IF_ACMPEQ, * IF_ACMPNE, PUTFIELD * * @param insn the bytecode instruction to be interpreted. * @param value1 the first argument of the instruction to be interpreted. * @param value2 the second argument of the instruction to be interpreted. * @return the result of the interpretation of the given instruction. * @throws AnalyzerException if an error occurred during the interpretation. */ public abstract V binaryOperation(AbstractInsnNode insn, V value1, V value2) throws AnalyzerException; /** * Interprets a bytecode instruction with three arguments. This method is called for the following * opcodes: * * <p>IASTORE, LASTORE, FASTORE, DASTORE, AASTORE, BASTORE, CASTORE, SASTORE * * @param insn the bytecode instruction to be interpreted. * @param value1 the first argument of the instruction to be interpreted. * @param value2 the second argument of the instruction to be interpreted. * @param value3 the third argument of the instruction to be interpreted. * @return the result of the interpretation of the given instruction. * @throws AnalyzerException if an error occurred during the interpretation. */ public abstract V ternaryOperation(AbstractInsnNode insn, V value1, V value2, V value3) throws AnalyzerException; /** * Interprets a bytecode instruction with a variable number of arguments. This method is called * for the following opcodes: * * <p>INVOKEVIRTUAL, INVOKESPECIAL, INVOKESTATIC, INVOKEINTERFACE, MULTIANEWARRAY and * INVOKEDYNAMIC * * @param insn the bytecode instruction to be interpreted. * @param values the arguments of the instruction to be interpreted. * @return the result of the interpretation of the given instruction. * @throws AnalyzerException if an error occurred during the interpretation. */ public abstract V naryOperation(AbstractInsnNode insn, List<? extends V> values) throws AnalyzerException; /** * Interprets a bytecode return instruction. This method is called for the following opcodes: * * <p>IRETURN, LRETURN, FRETURN, DRETURN, ARETURN * * @param insn the bytecode instruction to be interpreted. * @param value the argument of the instruction to be interpreted. * @param expected the expected return type of the analyzed method. * @throws AnalyzerException if an error occurred during the interpretation. */ public abstract void returnOperation(AbstractInsnNode insn, V value, V expected) throws AnalyzerException; /** * Merges two values. The merge operation must return a value that represents both values (for * instance, if the two values are two types, the merged value must be a common super type of the * two types. If the two values are integer intervals, the merged value must be an interval that * contains the previous ones. Likewise for other types of values). * * @param value1 a value. * @param value2 another value. * @return the merged value. If the merged value is equal to {@code value1}, this method * <i>must</i> return {@code value1}. */ public abstract V merge(V value1, V value2); }