Package org.objectweb.asm.tree.analysis

Class Interpreter<V extends Value>

java.lang.Object
org.objectweb.asm.tree.analysis.Interpreter<V>
Type Parameters:
V - type of the Value used for the analysis.
Direct Known Subclasses:
BasicInterpreter, SourceInterpreter
public abstract class Interpreter<V extends Value> extends Object
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 Analyzer to work with various semantic interpreters, without needing to duplicate the code to simulate the transfer of values.

  • Field Details

    • api

      protected final int api
      The ASM API version supported by this interpreter. The value of this field must be one of the ASMx values in Opcodes.

  • Constructor Details

    • Interpreter

      protected Interpreter(int api)
      Constructs a new Interpreter.
      Parameters:
      api - the ASM API version supported by this interpreter. Must be one of the ASMx values in Opcodes.

  • Method Details

    • newValue

      public abstract V newValue(Type type)
      Creates a new value that represents the given type.

      Called for method parameters (including this), exception handler variable and with null type for variables reserved by long and double types.

      An interpreter may choose to implement one or more of newReturnTypeValue(Type), newParameterValue(boolean, int, Type), newEmptyValue(int), newExceptionValue(TryCatchBlockNode, Frame, Type) to distinguish different types of new value.

      Parameters:
      type - a primitive or reference type, or null to represent an uninitialized value.
      Returns:
      a value that represents the given type. The size of the returned value must be equal to the size of the given type.

    • newParameterValue

      public V newParameterValue(boolean isInstanceMethod, int local, 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.

      By default, calls newValue(type).

      Parameters:
      isInstanceMethod - true if the method is non-static.
      local - the local variable index.
      type - a primitive or reference type.
      Returns:
      a value that represents the given type. The size of the returned value must be equal to the size of the given type.

    • newReturnTypeValue

      public V newReturnTypeValue(Type type)
      Creates a new value that represents the given return type. This method is called to initialize the return type value of a frame.

      By default, calls newValue(type).

      Parameters:
      type - a primitive or reference type.
      Returns:
      a value that represents the given type. The size of the returned value must be equal to the size of the given type.

    • newEmptyValue

      public V newEmptyValue(int local)
      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.

      By default, calls newValue(null).

      Parameters:
      local - the local variable index.
      Returns:
      a value representing an uninitialized value. The size of the returned value must be equal to 1.

    • newExceptionValue

      public V newExceptionValue(TryCatchBlockNode tryCatchBlockNode, Frame<V> handlerFrame, Type exceptionType)
      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.

      By default, calls newValue(exceptionType).

      Parameters:
      tryCatchBlockNode - the exception handler.
      handlerFrame - the exception handler frame.
      exceptionType - the exception type handled by this handler.
      Returns:
      a value that represents the given exceptionType. The size of the returned value must be equal to 1.

    • newOperation

      public abstract V newOperation(AbstractInsnNode insn) throws AnalyzerException
      Interprets a bytecode instruction without arguments. This method is called for the following opcodes:

      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

      Parameters:
      insn - the bytecode instruction to be interpreted.
      Returns:
      the result of the interpretation of the given instruction.
      Throws:
      AnalyzerException - if an error occurred during the interpretation.

    • copyOperation

      public abstract V copyOperation(AbstractInsnNode insn, V value) 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:

      ILOAD, LLOAD, FLOAD, DLOAD, ALOAD, ISTORE, LSTORE, FSTORE, DSTORE, ASTORE, DUP, DUP_X1, DUP_X2, DUP2, DUP2_X1, DUP2_X2, SWAP

      Parameters:
      insn - the bytecode instruction to be interpreted.
      value - the value that must be moved by the instruction.
      Returns:
      the result of the interpretation of the given instruction. The returned value must be equal to the given value.
      Throws:
      AnalyzerException - if an error occurred during the interpretation.

    • unaryOperation

      public abstract V unaryOperation(AbstractInsnNode insn, V value) throws AnalyzerException
      Interprets a bytecode instruction with a single argument. This method is called for the following opcodes:

      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

      Parameters:
      insn - the bytecode instruction to be interpreted.
      value - the argument of the instruction to be interpreted.
      Returns:
      the result of the interpretation of the given instruction.
      Throws:
      AnalyzerException - if an error occurred during the interpretation.

    • binaryOperation

      public abstract V binaryOperation(AbstractInsnNode insn, V value1, V value2) throws AnalyzerException
      Interprets a bytecode instruction with two arguments. This method is called for the following opcodes:

      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

      Parameters:
      insn - the bytecode instruction to be interpreted.
      value1 - the first argument of the instruction to be interpreted.
      value2 - the second argument of the instruction to be interpreted.
      Returns:
      the result of the interpretation of the given instruction.
      Throws:
      AnalyzerException - if an error occurred during the interpretation.

    • ternaryOperation

      public abstract V ternaryOperation(AbstractInsnNode insn, V value1, V value2, V value3) throws AnalyzerException
      Interprets a bytecode instruction with three arguments. This method is called for the following opcodes:

      IASTORE, LASTORE, FASTORE, DASTORE, AASTORE, BASTORE, CASTORE, SASTORE

      Parameters:
      insn - the bytecode instruction to be interpreted.
      value1 - the first argument of the instruction to be interpreted.
      value2 - the second argument of the instruction to be interpreted.
      value3 - the third argument of the instruction to be interpreted.
      Returns:
      the result of the interpretation of the given instruction.
      Throws:
      AnalyzerException - if an error occurred during the interpretation.

    • naryOperation

      public abstract V naryOperation(AbstractInsnNode insn, List<? extends V> values) throws AnalyzerException
      Interprets a bytecode instruction with a variable number of arguments. This method is called for the following opcodes:

      INVOKEVIRTUAL, INVOKESPECIAL, INVOKESTATIC, INVOKEINTERFACE, MULTIANEWARRAY and INVOKEDYNAMIC

      Parameters:
      insn - the bytecode instruction to be interpreted.
      values - the arguments of the instruction to be interpreted.
      Returns:
      the result of the interpretation of the given instruction.
      Throws:
      AnalyzerException - if an error occurred during the interpretation.

    • returnOperation

      public abstract void returnOperation(AbstractInsnNode insn, V value, V expected) throws AnalyzerException
      Interprets a bytecode return instruction. This method is called for the following opcodes:

      IRETURN, LRETURN, FRETURN, DRETURN, ARETURN

      Parameters:
      insn - the bytecode instruction to be interpreted.
      value - the argument of the instruction to be interpreted.
      expected - the expected return type of the analyzed method.
      Throws:
      AnalyzerException - if an error occurred during the interpretation.

    • merge

      public abstract V merge(V value1, V value2)
      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).
      Parameters:
      value1 - a value.
      value2 - another value.
      Returns:
      the merged value. If the merged value is equal to value1, this method must return value1.