branchtargetfinder.java

来自「proguard 一个java的混淆器」· Java 代码 · 共 689 行 · 第 1/2 页

        // Initialize the stack of 'new' instruction offsets if this method is
        // an instance initializer.
        if (method.getName(clazz).equals(ClassConstants.INTERNAL_METHOD_NAME_INIT))
        {
            recentCreationOffsets[recentCreationOffsetIndex++] = AT_METHOD_ENTRY;
        }

        // The end of the code is a branch target sentinel.
        instructionMarks[codeLength] = BRANCH_TARGET;

        // Mark branch targets by going over all instructions.
        codeAttribute.instructionsAccept(clazz, method, this);

        // Mark branch targets in the exception table.
        codeAttribute.exceptionsAccept(clazz, method, this);

        // Fill out any gaps in the subroutine starts and the subroutine ends
        // and subroutine returning flags, working backward.

        // We're not starting in a subroutine.
        int     subroutineStart     = NONE;
        int     subroutineEnd       = codeLength;
        boolean subroutineReturning = false;

        for (int index = codeLength - 1; index >= 0; index--)
        {
            if (isInstruction(index))
            {
                // Are we inside a previously marked subroutine?
                if (subroutineStarts[index] != NONE)
                {
                    // Update the current subroutine start.
                    subroutineStart = subroutineStarts[index];
                }
                else if (subroutineStart != NONE)
                {
                    // Mark the subroutine start.
                    subroutineStarts[index] = subroutineStart;
                }

                // Did we reach the start of the subroutine.
                if (isSubroutineStart(index))
                {
                    // Stop marking it.
                    subroutineStart = NONE;
                }

                // Are we inside a subroutine?
                if (isSubroutine(index))
                {
                    // Mark the subroutine end.
                    subroutineEnds[index] = subroutineEnd;

                    // Update or mark the subroutine returning flag.
                    if (isSubroutineReturning(index))
                    {
                        subroutineReturning = true;
                    }
                    else if (subroutineReturning)
                    {
                        instructionMarks[index] |= SUBROUTINE_RETURNING;
                    }
                }
                else
                {
                    // Update the subroutine end and returning flag.
                    subroutineEnd       = index;
                    subroutineReturning = false;
                }
            }
        }

        if (DEBUG)
        {
            System.out.println();
            System.out.println("Branch targets: "+clazz.getName()+"."+method.getName(clazz)+method.getDescriptor(clazz));

            for (int index = 0; index < codeLength; index++)
            {
                if (isInstruction(index))
                {
                    System.out.println("" +
                                       (isBranchOrigin(index)         ? 'B' : '-') +
                                       (isBranchTarget(index)         ? 'T' : '-') +
                                       (isExceptionStart(index)       ? 'E' : '-') +
                                       (isExceptionEnd(index)         ? 'E' : '-') +
                                       (isExceptionHandler(index)     ? 'H' : '-') +
                                       (isSubroutineInvocation(index) ? 'J' : '-') +
                                       (isSubroutineStart(index)      ? 'S' : '-') +
                                       (isSubroutineReturning(index)  ? 'r' : '-') +
                                       (isSubroutine(index)           ? " ["+subroutineStart(index)+" -> "+subroutineEnd(index)+"] " : " ") +
                                       InstructionFactory.create(codeAttribute.code, index).toString(index));
                }
            }
        }
    }


    // Implementations for InstructionVisitor.

    public void visitSimpleInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, SimpleInstruction simpleInstruction)
    {
        // Mark the instruction.
        instructionMarks[offset] |= INSTRUCTION;

        // Check if this is the first instruction of a subroutine.
        checkSubroutine(offset);

        byte opcode = simpleInstruction.opcode;
        if (opcode == InstructionConstants.OP_IRETURN ||
            opcode == InstructionConstants.OP_LRETURN ||
            opcode == InstructionConstants.OP_FRETURN ||
            opcode == InstructionConstants.OP_DRETURN ||
            opcode == InstructionConstants.OP_ARETURN ||
            opcode == InstructionConstants.OP_ATHROW)
        {
            // Mark the branch origin.
            markBranchOrigin(offset);

            // Mark the next instruction.
            markAfterBranchOrigin(offset + simpleInstruction.length(offset));
        }
    }


    public void visitConstantInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, ConstantInstruction constantInstruction)
    {
        // Mark the instruction.
        instructionMarks[offset] |= INSTRUCTION;

        // Check if this is the first instruction of a subroutine.
        checkSubroutine(offset);

        // Check if the instruction is a 'new' instruction.
        if (constantInstruction.opcode == InstructionConstants.OP_NEW)
        {
            // Push the 'new' instruction offset on the stack.
            recentCreationOffsets[recentCreationOffsetIndex++] = offset;
        }
        else
        {
            // Check if the instruction is an initializer invocation.
            isInitializer = false;
            clazz.constantPoolEntryAccept(constantInstruction.constantIndex, this);
            if (isInitializer)
            {
                // Pop the 'new' instruction offset from the stack.
                int recentCreationOffset = recentCreationOffsets[--recentCreationOffsetIndex];

                // Fill it out in the creation offsets.
                creationOffsets[offset] = recentCreationOffset;

                // Fill out the initialization offsets.
                if (recentCreationOffset == AT_METHOD_ENTRY)
                {
                    superInitializationOffset = offset;
                }
                else
                {
                    initializationOffsets[recentCreationOffset] = offset;
                }
            }
        }
    }


    public void visitVariableInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, VariableInstruction variableInstruction)
    {
        // Mark the instruction.
        instructionMarks[offset] |= INSTRUCTION;

        // Check if this is the first instruction of a subroutine.
        checkSubroutine(offset);

        if (variableInstruction.opcode == InstructionConstants.OP_RET)
        {
            // Mark the branch origin.
            markBranchOrigin(offset);

            // Mark the regular subroutine return.
            instructionMarks[offset] |= SUBROUTINE_RETURNING;

            // Mark the next instruction.
            markAfterBranchOrigin(offset + variableInstruction.length(offset));
        }
    }


    public void visitBranchInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, BranchInstruction branchInstruction)
    {
        // Mark the branch origin.
        markBranchOrigin(offset);

        // Check if this is the first instruction of a subroutine.
        checkSubroutine(offset);

        // Mark the branch target.
        markBranchTarget(offset, branchInstruction.branchOffset);

        byte opcode = branchInstruction.opcode;
        if (opcode == InstructionConstants.OP_JSR ||
            opcode == InstructionConstants.OP_JSR_W)
        {
            // Mark the subroutine invocation.
            instructionMarks[offset] |= SUBROUTINE_INVOCATION;

            // Mark the subroutine start.
            int targetOffset = offset + branchInstruction.branchOffset;
            subroutineStarts[targetOffset] = targetOffset;
        }
        else if (opcode == InstructionConstants.OP_GOTO ||
                 opcode == InstructionConstants.OP_GOTO_W)
        {
            // Mark the next instruction.
            markAfterBranchOrigin(offset + branchInstruction.length(offset));
        }
    }


    public void visitAnySwitchInstruction(Clazz clazz, Method method, CodeAttribute codeAttribute, int offset, SwitchInstruction switchInstruction)
    {
        // Mark the branch origin.
        markBranchOrigin(offset);

        // Check if this is the first instruction of a subroutine.
        checkSubroutine(offset);

        // Mark the branch targets of the default jump offset.
        markBranchTarget(offset, switchInstruction.defaultOffset);

        // Mark the branch targets of the jump offsets.
        markBranchTargets(offset,
                          switchInstruction.jumpOffsets);

        // Mark the next instruction.
        markAfterBranchOrigin(offset + switchInstruction.length(offset));
    }


    // Implementations for ConstantVisitor.

    public void visitAnyConstant(Clazz clazz, Constant constant) {}


    public void visitMethodrefConstant(Clazz clazz, MethodrefConstant methodrefConstant)
    {
        isInitializer = methodrefConstant.getName(clazz).equals(ClassConstants.INTERNAL_METHOD_NAME_INIT);
    }


    // Implementations for ExceptionInfoVisitor.

    public void visitExceptionInfo(Clazz clazz, Method method, CodeAttribute codeAttribute, ExceptionInfo exceptionInfo)
    {
        // Mark the exception offsets.
        instructionMarks[exceptionInfo.u2startPC]   |= EXCEPTION_START;
        instructionMarks[exceptionInfo.u2endPC]     |= EXCEPTION_END;
        instructionMarks[exceptionInfo.u2handlerPC] |= EXCEPTION_HANDLER;
    }


    // Small utility methods.

    /**
     * Marks the branch targets of the given jump offsets for the instruction
     * at the given offset.
     */
    private void markBranchTargets(int offset, int[] jumpOffsets)
    {
        for (int index = 0; index < jumpOffsets.length; index++)
        {
            markBranchTarget(offset, jumpOffsets[index]);
        }
    }


    /**
     * Marks the branch origin at the given offset.
     */
    private void markBranchOrigin(int offset)
    {
        instructionMarks[offset] |= INSTRUCTION | BRANCH_ORIGIN;
    }


    /**
     * Marks the branch target at the given offset.
     */
    private void markBranchTarget(int offset, int jumpOffset)
    {
        int targetOffset = offset + jumpOffset;

        instructionMarks[targetOffset] |= BRANCH_TARGET;

        // Are we inside a previously marked subroutine?
        if (isSubroutine(offset))
        {
            // Mark the subroutine start of the target.
            subroutineStarts[targetOffset] = currentSubroutineStart;

            // Update the current subroutine end.
            if (currentSubroutineEnd < targetOffset)
            {
                currentSubroutineEnd = targetOffset;
            }
        }
    }


    /**
     * Marks the instruction at the given offset, after a branch.
     */
    private void markAfterBranchOrigin(int nextOffset)
    {
        instructionMarks[nextOffset] |= AFTER_BRANCH;

        // Are we at the end of the current subroutine?
        if (currentSubroutineEnd <= nextOffset)
        {
            // Reset the subroutine start.
            currentSubroutineStart = NONE;
        }
    }


    /**
     * Checks if the specified instruction is inside a subroutine.
     */
    private void checkSubroutine(int offset)
    {
        // Are we inside a previously marked subroutine?
        if (isSubroutine(offset))
        {
            // Update the current subroutine start.
            currentSubroutineStart = subroutineStarts[offset];
        }
        else
        {
            // Mark the subroutine start (or NONE).
            subroutineStarts[offset] = currentSubroutineStart;
        }
    }
}