"forums_mp" <forums__mp@bellsouth.net> wrote in message
news:c9d2134e.0310051450.15173b15@posting.google.c om...[color=blue]
> I've got an STL class (see below) with two functions to store and
> retrieve data - msg structs.
>
> The "Store" function when called will copy the received message
> (depending on which message) into the appropriate array. For instance
> if I receive a RCVD_MSG1, I'll copy into msg1 [ 0 ]. Upon receipt of
> the next RCVD_MSG1. I'll copy into msg1 [ 1 ].
> The Retrieve function when called should retrieve the latest copy.
> ie. msg1 [ 0 ] or msg1 [ 1 ].
>
> I've made it this far and am unsure how best to implement this.
> One other thing. I suspect maps (not too familiar with maps but I
> vaguely recall seeing something similiar in a newsgroup recently .. )
> would be provide an more elegant approach but i'm unsure how to modify
> code to do this.
>
> Thanks
>
> ------------------
>
> #include <iostream.h>
>
> const Max = 20;
> const True = 1;
> const False = 0;
>
> struct {
> unsigned rcvd_item1 : 16;
> unsigned rcvd_item2 : 13;
> unsigned rcvd_item3 : 10;
> unsigned spare : 9;
> } RCVD_MSG1;
>
> struct {
> unsigned rcvd_item1 : 11;
> unsigned rcvd_item2 : 10;
> unsigned spare : 11;
> } RCVD_MSG2;
>
> RCVD_MSG2 msg2 [ 2 ];
> RCVD_MSG1 msg1 [ 2 ];
>
>
> template<class T> class Vector
> {
> struct
> {
> T Data; //field Data is type T ..
> // May need to make this T Data [ 2 ];
>
> int Defined; //field Defined is type int
> } Elements[Max]; //array of Max items
>
> public:
> Vector::Vector()
> //Creates an empty abstract array.
> {
> int Index;
>
> for (Index = 0; Index < Max; ++Index)
> Elements[Index].Defined = False;
> }
>
> void Vector::Init(T X)
> //Initialize all elements to X
> //Pre : Vector created and X defined.
> //Post: All elements set to X and marked as defined.
> {
> int Index;
>
> for (Index = 0; Index < Max; ++Index)
> {
> Elements[Index].Data = X;
> Elements[Index].Defined = True;
> }
> }
>
> void Vector::Store (T X, int I)
> //Stores X at position I in abstract array.
> //Pre : Vector created; X and I are defined.
> //Post: Elements[Index].Data is X and position I is defined.
> //Need to implement ping/pong approach of the stored sturcts.
> // i.e. first call to Store a RCVD_MSG1 would store at msg1 [ 0 ]
> // Next call would store at msg1 [ 1 ]
> {
> Elements[i].Data = X;
> Elements[i].Defined = True;
> }
>
> void Vector::Retrieve(T &X, int I, int &Success)
> //Copies the value stored at vector position I to X.
> //
> //Post: Returns value stored at position I through X and
> // set Success to True, if position defined; otherwise
> // Success set to False.
> // Retrieve the LATEST at all times .. msg1 [ 0 ] or msg1 [ 1 ];
>
> {
> Success = Elements[i].Defined;
> if (Success)
> X = Elements[i].Data;
> }
>
> };[/color]
I don't see how a map would help. I think you could do everything you need
with std::vector:
#include <vector>
#include <exception>
template <typename RCVD_MSG>
class messages
{
private:
std::vector<RCVD_MSG> m_vec;
public:
void store(RCVD_MSG msg)
{
m_vvec.push_back(msg);
}
RCVD_MSG retrieve()
{
if (m_vec.size() == 0)
throw std::exception("oops");
return m_vec.back();
}
int size() const // check this before calling retrieve to avoid
exceptions
{
return m_vec.size();
}
};
messages<RCVD_MSG1> m1;
messages<RCVD_MSG2> m2;
<untested code>
--
Cy
http://home.rochester.rr.com/cyhome/ 
STL Help with Store/Retrieve .. Maps 
