ZIG-IPC

Zig code example to use shared memory among processes, only works on POSIX.

How it works?

1. Use shm_open and mmap to create a shared memory block.

2. Use atomic operations to manage a boolean value (busy).

   pub inline fn lock(self: *Self, comptime value: bool) void {
       while (true) {
           _ = @cmpxchgStrong(bool, &self.ptr.busy, !value, value, .SeqCst, .SeqCst) orelse break;
       }
   }
   

   Updates on the rest memory block requires busy to be false, and set to true before the update.

Run this example

Build and start the server. Press CTRL+C to exit.

zig build # compiles against v0.11.0
zig-out/bin/ipc-server

Start the client in another terminal.

zig-out/bin/ipc-client

Example output

Server process:

pseudoc $ zig-out/bin/ipc-server 
Sorting(3): { 6, 80, 68 }
Sorted(3): { 6, 68, 80 }
Sorting(4): { 6, 68, 80, 87 }
Sorted(4): { 6, 68, 80, 87 }
Sorting(5): { 6, 68, 80, 87, 63 }
Sorted(5): { 6, 63, 68, 80, 87 }
Sorting(6): { 6, 63, 68, 80, 87, 3 }
Sorted(6): { 3, 6, 63, 68, 80, 87 }
Sorting(7): { 3, 6, 63, 68, 80, 87, 86 }
Sorted(7): { 3, 6, 63, 68, 80, 86, 87 }
Sorting(8): { 3, 6, 63, 68, 80, 86, 87, 33 }
Sorted(8): { 3, 6, 33, 63, 68, 80, 86, 87 }
Sorting(9): { 3, 6, 33, 63, 68, 80, 86, 87, 0 }
Sorted(9): { 0, 3, 6, 33, 63, 68, 80, 86, 87 }
Sorting(10): { 0, 3, 6, 33, 63, 68, 80, 86, 87, 13 }
Sorted(10): { 0, 3, 6, 13, 33, 63, 68, 80, 86, 87 }
Sorting(11): { 0, 3, 6, 13, 33, 63, 68, 80, 86, 87, 11 }
Sorted(11): { 0, 3, 6, 11, 13, 33, 63, 68, 80, 86, 87 }
Sorting(12): { 0, 3, 6, 11, 13, 33, 63, 68, 80, 86, 87, 70 }
Sorted(12): { 0, 3, 6, 11, 13, 33, 63, 68, 70, 80, 86, 87 }
Sorting(13): { 0, 3, 6, 11, 13, 33, 63, 68, 70, 80, 86, 87, 25 }
Sorted(13): { 0, 3, 6, 11, 13, 25, 33, 63, 68, 70, 80, 86, 87 }

Client process:

pseudoc $ zig-out/bin/ipc-client 
Filled(3): { 6, 80, 68 }
Appended(1): 87
Appended(2): 63
Appended(3): 3
Appended(4): 86
Appended(5): 33
Appended(6): 0
Appended(7): 13
Appended(8): 11
Appended(9): 70
Appended(10): 25

References

Atomic Ordering

C POSIX IPC example