Question

I have the following data i need to add in the void buffer:

MyStruct somedata; // some struct containing ints or floats etc.
string somestring;

How do i do this?

This is my buffer allocation:

void *buffer = (void *)malloc(datasize);

How do i add first the somedata into the buffer (, which takes lets say 20 bytes), and then after 20 bytes comes the string which is variable size. I was thinking to read the structs byte by byte and add to buffer, but that feels stupid, there must be some easier way…?

Edit: i want this to equal to: fwrite( struct1 ); fwrite( struct2 ); which are called sequentially, but instead of writing to file, i want to write to a void buffer.

Edit 2: Made it working, heres the code:

char *data = (char *)malloc(datasize);

unsigned int bufferoffset = 0;

for(...){
    MyStruct somedata; // some POD struct containing ints or floats etc.
    string somestring;

    ... stuff ...

    // add to buffer:
    memcpy(data+bufferoffset, &somedata, sizeof(MyStruct));
    bufferoffset += sizeof(MyStruct);
    memcpy(data+bufferoffset, somestring.c_str(), str_len); 
    bufferoffset += str_len;
}

Anything to fix?

Answer 1

memcpy(buffer, &somedata, sizeof(MyStruct));
strcpy(buffer + sizeof(MyStruct), somestring.c_str());

Which will copy the string as a c string.