Help for multiple class involved definition

[fl]

Hi,
I am new to C++. I do not understand why the following definition of
"request_in_port" is a pointer:
..............................
typedef tlm::tlm_generic_payload *gp_ptr; // generic payload
.. . . . .

sc_core::sc_port<sc_core::sc_fifo_in_if <gp_ptr> >
request_in_port;
.............................
because I find that "request_in_port->read()" is used in this way:

.............................
tlm::tlm_generic_payload *transaction_ptr; // transaction pointer
.. . . . . .
transaction_ptr = request_in_port->read(); // get request from
input fifo
.............................

I know that "gp_ptr" is a pointer, but what type does
"sc_core::sc_fifo_in_if <gp_ptr>" return?

"<sc_core::sc_fifo_in_if <gp_ptr> >" should be a class type?



"sc_fifo_in_if<T>" is given below:
.............................
//
----------------------------------------------------------------------------
// CLASS : sc_fifo_in_if<T>
//
// The sc_fifo<T> input interface class.
//
----------------------------------------------------------------------------

template <class T>
class sc_fifo_in_if
: public sc_fifo_nonblocking_in_if<T>,
public sc_fifo_blocking_in_if<T>
{
public:

// get the number of available samples
virtual int num_available() const = 0;

protected:
}
.........................
I am puzzled on why "request_in_port" is a pointer. Could you help me?
Thanks.



BTW, the fifo read() is as below.

.............................
// blocking read

template <class T>
inline
void
sc_fifo<T>::read( T& val_ )
{
while( num_available() == 0 ) {
sc_core::wait( m_data_written_event );
}
m_num_read ++;
buf_read( val_ );
request_update();
}

template <class T>
inline
T
sc_fifo<T>::read()
{
T tmp;
read( tmp );
return tmp;
}
.................................

 

[fl]

Hi,
I am new to C++. I do not understand why the following definition of
"request_in_port" is a pointer:
.............................
  typedef tlm::tlm_generic_payload  *gp_ptr;        // generic payload
. . . . .

    sc_core::sc_port<sc_core::sc_fifo_in_if  <gp_ptr> >
request_in_port;
............................
because I find that "request_in_port->read()" is used in this way:

............................
  tlm::tlm_generic_payload *transaction_ptr;    // transaction pointer
. . . . . .
    transaction_ptr = request_in_port->read();  // get request from
input fifo
............................

I know that "gp_ptr" is a pointer, but what type does
"sc_core::sc_fifo_in_if  <gp_ptr>" return?

"<sc_core::sc_fifo_in_if  <gp_ptr> >" should be a class type?

"sc_fifo_in_if<T>" is given below:
............................
//
---------------------------------------------------------------------------­-
//  CLASS : sc_fifo_in_if<T>
//
//  The sc_fifo<T> input interface class.
//
---------------------------------------------------------------------------­-

template <class T>
class sc_fifo_in_if
: public sc_fifo_nonblocking_in_if<T>,
  public sc_fifo_blocking_in_if<T>
{
public:

    // get the number of available samples
    virtual int num_available() const = 0;

protected:}

........................
I am puzzled on why "request_in_port" is a pointer. Could you help me?
Thanks.

BTW, the fifo read() is as below.

............................
// blocking read

template <class T>
inline
void
sc_fifo<T>::read( T& val_ )
{
    while( num_available() == 0 ) {
        sc_core::wait( m_data_written_event );
    }
    m_num_read ++;
    buf_read( val_ );
    request_update();

}

template <class T>
inline
T
sc_fifo<T>::read()
{
    T tmp;
    read( tmp );
    return tmp;}

................................

Hi,
I just find that there is a redefinenition of -> for:
"
sc_core::sc_port
"
See below please. So, the '->" in my original post does not mean
"request_in_port" is a pointer?
"->" has been redefined as a method indicator? Is it so used? Am I
right now? Thanks.






...................................

//
----------------------------------------------------------------------------
// CLASS : sc_port_b
//
// Abstract base class for class sc_port.
//
----------------------------------------------------------------------------

// allow to call methods provided by the first interface

template <class IF>
inline
IF*
sc_port_b<IF>:perator -> ()
{
if( m_interface == 0 ) {
report_error( SC_ID_GET_IF_, "port is not bound" );
}
return m_interface;
}
.....................................................................

 

[Nick Keighley]

I am new to C++. I do not understand why the following definition of
"request_in_port" is a pointer:
.............................
  typedef tlm::tlm_generic_payload  *gp_ptr;        // generic payload
. . . . .

    sc_core::sc_port<sc_core::sc_fifo_in_if  <gp_ptr> >
request_in_port;
............................
because I find that "request_in_port->read()" is used in this way:

............................
  tlm::tlm_generic_payload *transaction_ptr;    // transaction pointer
. . . . . .
    transaction_ptr = request_in_port->read();  // get request from
input fifo
............................

I know that "gp_ptr" is a pointer, but what type does
"sc_core::sc_fifo_in_if  <gp_ptr>" return?

it doesn't return anything. It's a template type not a function.

"<sc_core::sc_fifo_in_if  <gp_ptr> >" should be a class type?

well a type anyway

 

[Nick Keighley]

I just find that there is a redefinenition of -> for:
"
    sc_core::sc_port
"
See below please. So, the '->" in my original post does not mean
"request_in_port" is a pointer?

not necessarily, though it ought to have "pointer like" semantics
(that is is it should act like a pointer)

"->" has been redefined as a method indicator? Is it so used? Am I
right now? Thanks.

well, the -> operator has been redefined for this class. It's better
to think of all classes having a default operator->() (IMO)

//
---------------------------------------------------------------------------­-
//  CLASS : sc_port_b
//
//  Abstract base class for class sc_port.
//
---------------------------------------------------------------------------­-

// allow to call methods provided by the first interface

template <class IF>
inline
IF*
sc_port_b<IF>:perator -> ()
{
    if( m_interface == 0 ) {
        report_error( SC_ID_GET_IF_, "port is not bound" );
    }
    return m_interface;}

this is probably what C++ calls a "smart pointer". Your C++ reference
should be able to answer basic questions about templates and smart
pointers