Shared Memory

Shared memory is a memory area that is shared between two or more processes. It is a way to communicate between processes without the need for IPC. This is achieved by using a shared allocated memory area that is accessible by all the processes. The shared memory area is created using the shm_open function.

The shm_open is a system call that is used to create a shared memory area. A rust like implementation of this function can be made using the libc crate.:w

use libc;

fn shm_open(name: &str, oflag: i32, mode: i32) -> i32 {
    unsafe {
        libc::shm_open(name.as_ptr(), oflag, mode)
    }
}

In the scope of SWHKD, a shared memory area can be used to communicate between the parent process running in sudo and the child process running in the user space. We can allocate a simple data storage structure like a Vec<String> or a ring buffer to the shared memory area, that can then be written to by the parent process and read by the child process.

This should ideally be done using the mmap function. The mmap or the memory map function is a system call that is used to map a file into memory.

However, before I start to actually implement this and write the code, I wanted to make sure that this indeed is the rust-y way of doing things.

In the official rust documentation, I found a quote borrowed from the Go programming language documentation:

Do not communicate by sharing memory; instead, share memory by communicating.

This quote stuck out quite a bit to me. What this essentially means is that the ideal approach to communicating memory is not sharing the memory itself, but rather sharing the data that is stored in the memory. This statement is essentially a corollary pointing to the use of channels.

This quote does make a lot of sense. Would you rather pass a roti from the bowl or the whole bowl to a person? (Well ig you can do either, but think the bowl is heavy for something).

So in this regard, I think the ITC way to doing things seems a lot more natural. However, I am a bit interested in shm so, let’s assume that this is the way to go for a while and see how it goes.

So, I will be doing a lot of reading on this topic and see how it goes.