Implement deletion of SysV IPC message queues

As usual also the readme and the man page are updated.

src/lib.rs

@@ -1,9 +1,9 @@
 use libc::{
-    msgget, IPC_CREAT, IPC_EXCL, IPC_INFO, IPC_NOWAIT, IPC_PRIVATE, IPC_RMID, IPC_SET, IPC_STAT,
+    msgctl, msgget, msqid_ds, IPC_CREAT, IPC_EXCL, IPC_INFO, IPC_NOWAIT, IPC_PRIVATE, IPC_RMID,
-    MSG_COPY, MSG_EXCEPT, MSG_INFO, MSG_NOERROR, MSG_STAT,
+    IPC_SET, IPC_STAT, MSG_COPY, MSG_EXCEPT, MSG_INFO, MSG_NOERROR, MSG_STAT,
 };
 use nix::errno::{errno, Errno};
-use std::{marker::PhantomData, num::ParseIntError};
+use std::{marker::PhantomData, num::ParseIntError, ptr};
 use thiserror::Error;
 
 #[derive(Debug, Error)]
@@ -54,6 +54,27 @@ pub enum ControlCommands {
     MsgInfo = MSG_INFO,
 }
 
+pub fn unlink_id(id: i32) -> Result<(), SysvMqError> {
+    let res = unsafe {
+        msgctl(
+            id,
+            ControlCommands::Remove as i32,
+            ptr::null::<msqid_ds>() as *mut msqid_ds,
+        )
+    };
+
+    match res {
+        -1 => Err(SysvMqError::ErrnoError(Errno::from_i32(errno()).desc())),
+        _ => Ok(()),
+    }
+}
+
+pub fn unlink_key(key: i32) -> Result<(), SysvMqError> {
+    let id = unsafe { msgget(key, 0) };
+
+    unlink_id(id)
+}
+
 pub struct SysvMq<T> {
     pub id: i32,
     pub key: i32,