org.objectweb.asm.tree.analysis
Interface Interpreter

All Known Implementing Classes:
BasicInterpreter, BasicVerifier, SimpleVerifier, SourceInterpreter

public interface Interpreter

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.

Author:
Eric Bruneton

Method Summary
 Value binaryOperation(AbstractInsnNode insn, Value value1, Value value2)
          Interprets a bytecode instruction with two arguments.
 Value copyOperation(AbstractInsnNode insn, Value value)
          Interprets a bytecode instruction that moves a value on the stack or to or from local variables.
 Value merge(Value v, Value w)
          Merges two values.
 Value naryOperation(AbstractInsnNode insn, List values)
          Interprets a bytecode instruction with a variable number of arguments.
 Value newOperation(AbstractInsnNode insn)
          Interprets a bytecode instruction without arguments.
 Value newValue(Type type)
          Creates a new value that represents the given type.
 Value ternaryOperation(AbstractInsnNode insn, Value value1, Value value2, Value value3)
          Interprets a bytecode instruction with three arguments.
 Value unaryOperation(AbstractInsnNode insn, Value value)
          Interprets a bytecode instruction with a single argument.
 

Method Detail

newValue

Value 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.

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.

newOperation

Value 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 occured during the interpretation.

copyOperation

Value copyOperation(AbstractInsnNode insn,
                    Value 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 occured during the interpretation.

unaryOperation

Value unaryOperation(AbstractInsnNode insn,
                     Value 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 occured during the interpretation.

binaryOperation

Value binaryOperation(AbstractInsnNode insn,
                      Value value1,
                      Value 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 occured during the interpretation.

ternaryOperation

Value ternaryOperation(AbstractInsnNode insn,
                       Value value1,
                       Value value2,
                       Value 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 occured during the interpretation.

naryOperation

Value naryOperation(AbstractInsnNode insn,
                    List 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

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 occured during the interpretation.

merge

Value merge(Value v,
            Value w)
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:
v - a value.
w - another value.
Returns:
the merged value. If the merged value is equal to v, this method must return v.