Pointer aritmetics?

>>++ptr;

Instead of the above, do the following:
ptr =  (Header*) ( ( (char*) ptr) + 1);

FYI:

I recommend not using void, and instead use the correct type.
I also recommend not using malloc, and instead use new

I just notice ptr is not a pointer, and instead is an integer.
The code I posted would be appropriate if ptr was a pointer of type Header.

In any case, if you want to increment a struct pointer by single byte, you still need to cast it to a single byte type, as in the example I posted.

btw, this :

        header_ptr = static_cast<Header*>(HeaderBuffer) + ptr;
        ++ptr;

is the same as :

        ++header_ptr;

No need to make things more complicated than they are :)

For the answer to your question, ignore this post and check Axter's posts.

char* tmp_ptr = static_cast<char*>(HeaderBuffer) + ptr;
header_ptr = static_cast<Header*>(tmp_ptr);

[C++ Error] filehandler.cpp(35): E2031 Cannot cast from 'char *' to 'Header *'????

But if use the c standard

header_ptr = (Header*) tmp_ptr;

I get it to work, why? Should I leave it or is there a way to use the C++ standard?

>> I would like the header_ptr to be incremented by on byte.

>>I would prefer to keep the header_ptr to be a Header* pointer since then i can use the struct to check the values,
the values vary from 16 to 32 bit.

This two lines are contardictory, cause if you want the header pointer by one byte keeping it as Header* you will certainly not get the appropiate or correct value for the field you are going to use as the pointer increament by one byte and will load data after that byte which will definitly give you improper values in their fields.

let me give you a simple example to clarify:

struct TEMP
            {
                  char a,b,c;
            }ttr[10];

//somewhere in the code you initialize the buffer
char a='a';

for(int i=0; i < 10; i++)
      {
            ttr[i].a=a++;
            ttr[i].b=a++;
            ttr[i].c=a++;
      }

TEMP* st=ttr;
for(i=0; i < 10; i++)
      {
                 printf("%c %c %c\n",st->a,st->b,st->c);
            st=(TEMP*)(((char*)st)+1);
      }

just see the values it prints. cause its not what you are expecting

even if u still want to traverse the struct by one byte you can do the following

header_ptr=(Header*)(((char*)header_ptr)+1);

this will increament header_ptr by one byte

Hope this helps

Nafis

Hi nafis_devlpr thanks for the answer.
 
This is the struct that i am using
typedef struct{
        //--------HEADERS-------
        unsigned __int16 STX;
      unsigned __int16 CRC;
        unsigned __int16 MachID;
        unsigned __int16 ClinicalSWID;
        unsigned __int32 MsgCounter;
        unsigned __int32 CmdCode;
        unsigned __int32 MsgInfo;
        unsigned __int32 Flags;
        unsigned __int32 PatId1;
        unsigned __int32 PatId2;
        unsigned __int32 PatId3;
        unsigned __int32 SWRevision;
        unsigned __int32 Time;
        unsigned __int32 MBL;
        //----------------------
}Header;

when i find the 0x0002 i have to check the rest of the variabels.

iStream.read(static_cast<char*>(HeaderBuffer),6400);
Header* header_ptr = static_cast<Header*>(HeaderBuffer);
int ptr = 1;
while(header_ptr->STX != 0x0002 && ptr <= 6400) {
         char* tmp_ptr = static_cast<char*>(HeaderBuffer) + ptr;
         header_ptr = (Header*) tmp_ptr;
         ++ptr;
}
...
.....
memcpy(HeaderBuffer, header_ptr, static_cast<unsigned int>(32000-ptr));
header = static_cast<Header*>(HeaderBuffer);
..
....
//Checking the other variabels..
...
.

So I think I got it. But i will change it in the while loop to what Infinity08 has writen.
Thanks.