Question

I can’t find anything on the net that tells how to put a data type into a pre-allocated block of memory. I hate doing memory management myself, but in this case I must.

I have a block of memory that is 10 bytes long. (My app is 64bit using Visual C.) What I want to be able to do is put 1 unsigned int into bytes 0-3, a char into [4] and char into [5], and another unsigned int into [6-9].

I tried ssprintf already.

So I’m trying to figure out a way to 1) store it into this block of memory and 2) retrieve it.

Answer 1

IMO, a good way to accomplish that is by defining a struct containing the data you described:

#pragma pack(1)
struct complex {
    uint32_t a; // 4 bytes
    char b[2]; // 2 bytes (without paddding)
    uint32_t c; // 4 bytes
};

Then you can simply fill in your data:

struct complex var;
var.a = 10;
var.b[0] = 'x';
var.b[1] = 'y';
var.c = 20;

Note the #pragma pack(1) directive tells the compiler to use a 1-byte alignment. If you don’t know what it means, you can read about data structure alignment.