infer.cxx

ecos实时嵌入式操作系统

                return result;
            }
        }
        if (CdlInfer::set_valuable_bool(transaction, valuable, true, level)) {
            result = true;
        }

    } else {
        // If the valuable should evaluate to false then it must be either
        // inactive or it must be disabled or have a zero value.
        if (!transaction->is_active(valuable)) {
            // The goal is already satisfied, no need to proceed
            result = true;
            CYG_REPORT_RETVAL(result);
            return result;
        }
        
        // There is a choice to be made so two sub-transactions are
        // needed. Disabling is generally preferred to making inactive.
        CdlTransaction value_transaction    = transaction->make(transaction->get_conflict());
        CdlTransaction inactive_transaction = 0;
        bool value_result = CdlInfer::set_valuable_bool(value_transaction, valuable, false, level);
        if (value_result && !value_transaction->user_confirmation_required()) {
            value_transaction->commit();
            delete value_transaction;
            value_transaction = 0;
            result = true;
            CYG_REPORT_RETVAL(result);
            return result;
        }

        inactive_transaction = transaction->make(transaction->get_conflict());
        bool inactive_result = CdlInfer::make_inactive(inactive_transaction, valuable, level);
        if (!inactive_result) {
            if (value_result) {
                // Changing the value is the only solution.
                inactive_transaction->cancel();
                value_transaction->commit();
                result = true;
            } else {
                inactive_transaction->cancel();
                value_transaction->cancel();
                result = false;
            }
        } else {
            if (!value_result) {
                // Making the valuable inactive is the only solution.
                value_transaction->cancel();
                inactive_transaction->commit();
                result = true;
            } else if (!inactive_transaction->user_confirmation_required()) {
                // Disabling the valuable would require user confirmation, making it inactive does not
                value_transaction->cancel();
                inactive_transaction->commit();
                result = true;
            } else {
                // Both approaches are valid but would require user confirmation.
                // Pick the preferred one.
                if (value_transaction->is_preferable_to(inactive_transaction)) {
                    inactive_transaction->cancel();
                    value_transaction->commit();
                    result = true;
                } else {
                    value_transaction->cancel();
                    inactive_transaction->commit();
                    result = true;
                }
            }
        }

        delete value_transaction;
        delete inactive_transaction;
        value_transaction = 0;
        inactive_transaction = 0;
    }
    
    CYG_REPORT_RETVAL(result);
    return result;
}

// ----------------------------------------------------------------------------
// Try to set a valuable to a particular value. Of course the reference
// may not be bound yet.
//
// First check whether or not the valuable is currently active. If it is
// inactive and the goal is 0 then we have succeeded. If it is active and
// the goal is 0 then we could try to make the valuable inactive, but
// this possibility is ignored for now in case it leads to unexpected
// behaviour. If it is active then we try to set the value, using
// CdlInfer::set_valuable_value().

static bool
infer_handle_reference_value(CdlTransaction transaction, CdlValuable valuable, CdlSimpleValue& goal, int level)
{
    CYG_REPORT_FUNCNAMETYPE("infer_handle_reference", "result %d");
    CYG_REPORT_FUNCARG3XV(transaction, valuable, level);

    bool result = false;

    if (0 == valuable) {
        if (goal == (cdl_int) 0) {
            result = true;
        }
    } else {
    
        bool active = transaction->is_active(valuable);
        if (!active) {
            if (goal == (cdl_int) 0) {
                result = true;
            }
        } else {
            result = CdlInfer::set_valuable_value(transaction, valuable, goal, level);
        }
    }
    
    CYG_REPORT_RETVAL(result);
    return result;
}

//}}}
//{{{  infer_handle_xxx_constant()              

// ----------------------------------------------------------------------------
// Somewhere in the expression processing we have encountered a string
// constant. The expression cannot be changed, so either the goal matches
// the constant or it does not.
static bool
infer_handle_string_constant_bool(CdlSimpleValue& constant, bool goal)
{
    CYG_REPORT_FUNCNAMETYPE("infer_handle_string_constant_bool", "result %d");
    bool result = false;

    if (goal) {
        if (("" != constant.get_value()) && ("0" != constant.get_value())) {
            result = true;
        }
    } else {
        if (("" == constant.get_value()) || ("0" == constant.get_value())) {
            result = true;
        }
    }

    CYG_REPORT_RETVAL(result);
    return result;
}

static bool
infer_handle_string_constant_value(CdlSimpleValue& constant, CdlSimpleValue& goal)
{
    CYG_REPORT_FUNCNAMETYPE("infer_handle_string_constant_value", "result %d");
    bool result = false;

    if (constant.get_value() == goal.get_value()) {
        result = true;
    }

    CYG_REPORT_RETVAL(result);
    return result;
}

// ----------------------------------------------------------------------------
// Integers are also fairly straightforward.
static bool
infer_handle_integer_constant_bool(CdlSimpleValue& constant, bool goal)
{
    CYG_REPORT_FUNCNAMETYPE("infer_handle_integer_constant_bool", "result %d");
    CYG_PRECONDITIONC(constant.has_integer_value());
    bool result = false;

    if (goal) {
        if (0 != constant.get_integer_value()) {
            result = true;
        }
    } else {
        if (0 == constant.get_integer_value()) {
            result = true;
        }
    }
    
    CYG_REPORT_RETVAL(result);
    return result;
}

static bool
infer_handle_integer_constant_value(CdlSimpleValue& constant, CdlSimpleValue& goal)
{
    CYG_REPORT_FUNCNAMETYPE("infer_handle_integer_constant_value", "result %d");
    CYG_PRECONDITIONC(constant.has_integer_value());
    bool result = false;

    if (goal.has_integer_value() && (constant.get_integer_value() == goal.get_integer_value())) {
        result = true;
    }

    CYG_REPORT_RETVAL(result);
    return result;
}

// ----------------------------------------------------------------------------
// Doubles are also straightforward, except than an exact comparision may
// be too strict. There is not a lot that can be done about this right now.
// Future enhancements to CDL may support tolerances.
static bool
infer_handle_double_constant_bool(CdlSimpleValue& constant, bool goal)
{
    CYG_REPORT_FUNCNAMETYPE("infer_handle_double_constant_bool", "result %d");
    CYG_PRECONDITIONC(constant.has_double_value());
    bool result = false;

    if (goal) {
        if (0.0 != constant.get_double_value()) {
            result = true;
        }
    } else {
        if (0.0 == constant.get_double_value()) {
            result = true;
        }
    }

    CYG_REPORT_RETVAL(result);
    return result;
}

static bool
infer_handle_double_constant_value(CdlSimpleValue& constant, CdlSimpleValue& goal)
{
    CYG_REPORT_FUNCNAMETYPE("infer_handle_double_constant_value", "result %d");
    CYG_PRECONDITIONC(constant.has_double_value());
    bool result = false;

    if (goal.has_double_value() && (constant.get_double_value() == goal.get_double_value())) {
        result = true;
    }

    CYG_REPORT_RETVAL(result);
    return result;
}

//}}}
//{{{  infer_handle_logical_xxx()               

// ----------------------------------------------------------------------------
// Logical not simply involves inverting the goal and then trying to infer
// the rest of the sub-expression. There is little point in touching
// the other arguments.
static bool
infer_handle_logical_NOT_bool(CdlTransaction transaction, CdlExpression expr, unsigned int index, bool goal, int level)
{
    CYG_REPORT_FUNCNAMETYPE("infer_handle_logical_NOT_bool", "result %d");

    bool result = CdlInfer::subexpr_bool(transaction, expr, index, !goal, level);
    CYG_REPORT_RETVAL(result);
    return result;
}

// ----------------------------------------------------------------------------
// Depending on the goal, we want either both sides of the AND to evaluate to
// true, or we want one of the sides to evaluate to false.
static bool
infer_handle_AND_bool(CdlTransaction transaction, CdlExpression expr, unsigned int lhs, unsigned int rhs,
                      bool goal, int level)
{
    CYG_REPORT_FUNCNAMETYPE("infer_handle_AND_bool", "result %d");
    CYG_REPORT_FUNCARG4XV(transaction, expr, lhs, rhs);
    CYG_PRECONDITION_CLASSC(transaction);
    CYG_PRECONDITION_CLASSC(expr);
    CYG_PRECONDITIONC(lhs != rhs);

    bool result = false;
    
    if (goal) {
        // Both sides must be true in the same transaction, in case
        // the solutions overlap in conflicting ways. A sub-transaction
        // is still used to avoid polluting current values if the lhs
        // can be inferred but not the rhs.
        CdlTransaction sub_transaction = transaction->make(transaction->get_conflict());
        if (CdlInfer::subexpr_bool(sub_transaction, expr, lhs, true, level) &&
            CdlInfer::subexpr_bool(sub_transaction, expr, rhs, true, level)) {
            sub_transaction->commit();
            result = true;
        } else {
            sub_transaction->cancel();
        }
        delete sub_transaction;
    } else {
        // We need to try out both sides of the OR and see which one is preferable.
        // An optimization would be to only try the LHS, but trying both allows
        // for a more informed choice.
        CdlTransaction lhs_transaction = transaction->make(transaction->get_conflict());
        CdlTransaction rhs_transaction = transaction->make(transaction->get_conflict());
        bool lhs_result = CdlInfer::subexpr_bool(lhs_transaction, expr, lhs, false, level);
        bool rhs_result = CdlInfer::subexpr_bool(rhs_transaction, expr, rhs, false, level);

        result = infer_choose2(lhs_transaction, lhs_result, rhs_transaction, rhs_result);
    }

    CYG_REPORT_RETVAL(result);
    return result;
}

// ----------------------------------------------------------------------------
// The support for the other logical operations involves basically minor
// variants of the above.

static bool
infer_handle_OR_bool(CdlTransaction transaction, CdlExpression expr, unsigned int lhs, unsigned int rhs,
                     bool goal, int level)
{
    CYG_REPORT_FUNCNAMETYPE("infer_handle_OR_bool", "result %d");
    CYG_REPORT_FUNCARG4XV(transaction, expr, lhs, rhs);
    CYG_PRECONDITION_CLASSC(transaction);
    CYG_PRECONDITION_CLASSC(expr);
    CYG_PRECONDITIONC(lhs != rhs);


    bool result = false;
    
    if (goal) {
        // We need to try out both sides of the OR and see which one is preferable.
        // An optimization would be to only try the LHS, but trying both allows
        // for a more informed choice.
        CdlTransaction lhs_transaction = transaction->make(transaction->get_conflict());
        CdlTransaction rhs_transaction = transaction->make(transaction->get_conflict());
        bool lhs_result = CdlInfer::subexpr_bool(lhs_transaction, expr, lhs, true, level);
        bool rhs_result = CdlInfer::subexpr_bool(rhs_transaction, expr, rhs, true, level);

        result = infer_choose2(lhs_transaction, lhs_result, rhs_transaction, rhs_result);
    } else {
        
        // !(A || B) -> !A && !B
        CdlTransaction sub_transaction = transaction->make(transaction->get_conflict());