Class BasicBlocker

java.lang.Object
com.android.dx.cf.code.BasicBlocker
All Implemented Interfaces:
BytecodeArray.Visitor
public final class BasicBlocker extends Object implements BytecodeArray.Visitor
Utility that identifies basic blocks in bytecode.

  • Method Summary

    Modifier and Type
    Method
    Description
    int
    getPreviousOffset()
    Get previous bytecode offset
    static ByteBlockList
    identifyBlocks(ConcreteMethod method)
    Identifies and enumerates the basic blocks in the given method, returning a list of them.
    void
    setPreviousOffset(int offset)
    Set previous bytecode offset
    void
    visitBranch(int opcode, int offset, int length, int target)
    Visits an instruction which has a branch target argument.
    void
    visitConstant(int opcode, int offset, int length, Constant cst, int value)
    Visits an instruction which has a (possibly synthetic) constant argument, and possibly also an additional literal integer argument.
    void
    visitInvalid(int opcode, int offset, int length)
    Visits an invalid instruction.
    void
    visitLocal(int opcode, int offset, int length, int idx, Type type, int value)
    Visits an instruction which has a local variable index argument.
    void
    visitNewarray(int offset, int length, CstType type, ArrayList<Constant> intVals)
    Visits a newarray instruction.
    void
    visitNoArgs(int opcode, int offset, int length, Type type)
    Visits an instruction which has no inline arguments (implicit or explicit).
    void
    visitSwitch(int opcode, int offset, int length, SwitchList cases, int padding)
    Visits a switch instruction.

    Methods inherited from class Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Method Details

    • identifyBlocks

      public static ByteBlockList identifyBlocks(ConcreteMethod method)
      Identifies and enumerates the basic blocks in the given method, returning a list of them. The returned list notably omits any definitely-dead code that is identified in the process.
      Parameters:
      method - non-null; method to convert
      Returns:
      non-null; list of basic blocks

    • visitInvalid

      public void visitInvalid(int opcode, int offset, int length)
      Visits an invalid instruction.
      Specified by:
      visitInvalid in interface BytecodeArray.Visitor
      Parameters:
      opcode - the opcode
      offset - offset to the instruction
      length - length of the instruction, in bytes

    • visitNoArgs

      public void visitNoArgs(int opcode, int offset, int length, Type type)
      Visits an instruction which has no inline arguments (implicit or explicit).
      Specified by:
      visitNoArgs in interface BytecodeArray.Visitor
      Parameters:
      opcode - the opcode
      offset - offset to the instruction
      length - length of the instruction, in bytes
      type - non-null; type the instruction operates on

    • visitLocal

      public void visitLocal(int opcode, int offset, int length, int idx, Type type, int value)
      Visits an instruction which has a local variable index argument.
      Specified by:
      visitLocal in interface BytecodeArray.Visitor
      Parameters:
      opcode - the opcode
      offset - offset to the instruction
      length - length of the instruction, in bytes
      idx - the local variable index
      type - non-null; the type of the accessed value
      value - additional literal integer argument, if salient (i.e., for iinc)

    • visitConstant

      public void visitConstant(int opcode, int offset, int length, Constant cst, int value)
      Visits an instruction which has a (possibly synthetic) constant argument, and possibly also an additional literal integer argument. In the case of multianewarray, the argument is the count of dimensions. In the case of invokeinterface, the argument is the parameter count or'ed with the should-be-zero value left-shifted by 8. In the case of entries of type int, the value field always holds the raw value (for convenience of clients).

      Note: In order to avoid giving it a barely-useful visitor all its own, newarray also uses this form, passing value as the array type code and cst as a CstType instance corresponding to the array type.

      Specified by:
      visitConstant in interface BytecodeArray.Visitor
      Parameters:
      opcode - the opcode
      offset - offset to the instruction
      length - length of the instruction, in bytes
      cst - non-null; the constant
      value - additional literal integer argument, if salient (ignore if not)

    • visitBranch

      public void visitBranch(int opcode, int offset, int length, int target)
      Visits an instruction which has a branch target argument.
      Specified by:
      visitBranch in interface BytecodeArray.Visitor
      Parameters:
      opcode - the opcode
      offset - offset to the instruction
      length - length of the instruction, in bytes
      target - the absolute (not relative) branch target

    • visitSwitch

      public void visitSwitch(int opcode, int offset, int length, SwitchList cases, int padding)
      Visits a switch instruction.
      Specified by:
      visitSwitch in interface BytecodeArray.Visitor
      Parameters:
      opcode - the opcode
      offset - offset to the instruction
      length - length of the instruction, in bytes
      cases - non-null; list of (value, target) pairs, plus the default target
      padding - the bytes found in the padding area (if any), packed

    • visitNewarray

      public void visitNewarray(int offset, int length, CstType type, ArrayList<Constant> intVals)
      Visits a newarray instruction.
      Specified by:
      visitNewarray in interface BytecodeArray.Visitor
      Parameters:
      offset - offset to the instruction
      length - length of the instruction, in bytes
      type - non-null; the type of the array
      intVals - non-null; list of bytecode offsets for init values

    • setPreviousOffset

      public void setPreviousOffset(int offset)
      Set previous bytecode offset
      Specified by:
      setPreviousOffset in interface BytecodeArray.Visitor
      Parameters:
      offset - offset of the previous fully parsed bytecode

    • getPreviousOffset

      public int getPreviousOffset()
      Get previous bytecode offset
      Specified by:
      getPreviousOffset in interface BytecodeArray.Visitor
      Returns:
      return the recored offset of the previous bytecode