Re: Returning pointers which point to an array of structures

Hello,

Its a C question ! I need alot of advice on this one and therefore I am
thanking all in advance for any help that you can provide.

When my main program calls TCP_LOAD_MCB_X function (shown below) it passes
an integer variable called "j". Depending on the value of "j" I would like to
create an array of structures of either type MCB1, MCB2 or MCB3.

So if j = 0 when passed into TCP_LOAD_MCB_X function, then "j" further
passed to SizeMCB_X function which returns a pointer to MCB1 structure and
then I assign all 12 items based on this pointer.

But what happens when "j" = equal to 1? Will SizeMCB_X function still return
a pointer to MCB1 structure or will it return a pointer to MCB2 structure? My
guess is it will return it to MCB2 structure. And now here start the problems!

When "j" is returned from SizeMCB_X function, I need it to be able to be
used with the 12 strucuture items accroding to the strucuture being pointed
to like this:

//When j = 0:
pMCB1[i].ENDOFCHAR = MCB_FLASH_BUFFER[k];k++;
....

//When j = 1:
pMCB2[i].ENDOFCHAR = MCB_FLASH_BUFFER[k];k++;
....

//When j = 2:
pMCB3[i].ENDOFCHAR = MCB_FLASH_BUFFER[k];k++;
....

In other words I would require that the pointer returned be pointing to the
right strucuture so I can then use it. I know there are different ways of
structuring this program so that this can be acheived. But I must keep the
same structre as shown here, meaning that the three structures declared for
global scope in header file, the TCP_LOAD_MCB_X function calls the SizeMCB_X
function where the arrays of structures are created and returns its
respective pointer to one of the arrays of structures. And then the
assignment of the structure items are done in TCP_LOAD_MCB_X.

I am sorry for asking advice on this but I don't know what esle to try, I
have tried to declare all the MCB's strucutures in SizeMCB_X, but then all
the other functions in the C file don't have access to the items anymore...
so that was no good!

I tried assigning the pointer returned to another integer pointer declared
in TCP_LOAD_MCB_X function but that didn't work because it is expecting a
struct type pointer and I don't know how I can create a struct type pointer
for just general use.

I am confused on this one. As I go on my application constantly demands more
flexibility and I don't know all the possibilities that can be done with
structures. Perhaps an array of pointers which contain the locations of
MCB1,MCB2 and MCB3 and pass this to SizeMCB_X, could be a solution. I don't
know!

Can someone please guide on what would be the best way to acheive this. Here
is the code below which can give you a better idea of what I am trying to
accomplish:

//Declaring three structures and a pointer type for each structure
=====================================Header
struct MCB1{
int a; int b; };
struct MCB1* pMCB1;

struct MCB2{
int a; int b; };
struct MCB2* pMCB2;

struct MCB3{
int a; int b; };
struct MCB3* pMCB3;

//GRAPHICS MASTER INFORMATIONS FOR CURRENT FONT
struct GMI{
int MSG; //MESSAGE NUMBER
int msgA0; //LSB MESSAGE ADDERSS START
int msgA1; //MIDSB MESSAGE ADDERSS START
int msgA2; //MSB MESSAGE ADDERSS START
int CHARHIEGHT; //HIEGHT OF CHARACTERS
int CHARWIDTH; //CHARACTER WIDTH
int CHARSINMSG; //NUMBER OF CHARACTERS IN THIS MESSAGE
}aGMI[3];

===============================================Function
void TCP_LOAD_MCB_X(int j)
{
int i,k;
struct MCB1 *pMCB1;
....
....
pMCB1 = SizeMCB_X(j); //Size & create array of MCB structure
                           
for(i=0;i<20;i++)
{
k=0;
pMCB1[i].ENDOFCHAR = MCB_FLASH_BUFFER[k];k++;
pMCB1[i].A2 = MCB_FLASH_BUFFER[k];k++;
pMCB1[i].A1 = MCB_FLASH_BUFFER[k];k++;
pMCB1[i].A0 = MCB_FLASH_BUFFER[k];k++;
pMCB1[i].LEADING_PIX = MCB_FLASH_BUFFER[k];k++;
pMCB1[i].TRAILING_PIX = MCB_FLASH_BUFFER[k];k++;
pMCB1[i].CHARSPACING = MCB_FLASH_BUFFER[k];k++;
pMCB1[i].CHAR_TRSP = MCB_FLASH_BUFFER[k];k++;
pMCB1[i].mCHAR_BCOLOR = MCB_FLASH_BUFFER[k];k++;
pMCB1[i].lCHAR_BCOLOR = MCB_FLASH_BUFFER[k];k++;
pMCB1[i].mTEXT_COLOR = MCB_FLASH_BUFFER[k];k++;
pMCB1[i].lTEXT_COLOR = MCB_FLASH_BUFFER[k];k++;
}
.....
============================================
struct MCB1 *SizeMCB_X(int j)
{
//The next line simply defines the __CTNRSIZE (Container size) label based on
//the CHARSINMSG item of another structure. The next line is really not
relevant
//to the current question!!!!!!!!!!!!!!!!
#define __CTNRSIZE_X ((aGMI[m].CHARSINMSG)*16)

switch (j)
   {
      case 0:
         //Assign the address of an array of n structres created in heap to
a pointer !
         return (malloc(__CTNRSIZE_X*(sizeof(struct MCB1))));
         break;
      case 1:
         //Assign the address of an array of n structres created in heap to
a pointer !
         return (malloc(__CTNRSIZE_X*(sizeof(struct MCB2))));
         break;
      case 2:
         //Assign the address of an array of n structres created in heap to
a pointer !
         return (malloc(__CTNRSIZE_X*(sizeof(struct MCB3))));
         break;
      default:
         break;
   }
}

I appolagize for the lenghty post! Happy holidays everyone!