Question

I’m trying to create an array of structs as a sort of rudimentary cache.

Given a void* pointer to a mmap, does mmap provide any affordances for indexing into it? I think conceptually a mmap is simply providing a block of memory, but then I’m a bit confused as to what I can do with it. Can I just think of it as a malloc?

void * mptr = mmap(NULL, 1024*1024, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0);

Thanks for any clarification here.

Answer 1

Yes, you can think of it as a malloc, but you must deallocate it with munmap(mptr,1024*1024) rather than free(mptr).

If you want to index into it, cast it to another type, for example char:

char *cptr = (char*) mptr; 

Then you can index into it using cptr[10], for example.