sysvmq: Implement send and recv and refactor

Implement sending to and receiving from SysV IPC message queues. While
at it refactor the whole library. Write documentation for the sysvmq
library.

CHANGELOG.md

@@ -8,8 +8,37 @@ adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [Unreleased]
 
+### Added
+
+- Basic tests to create, send, receive and delete a message queue as
+  well as changing the mode of a queue.
+- The functions `SysvMq::stat()`, `SysvMq::info()`,
+  `SysvMq::msg_stat()` and `SysvMq::msg_info()` are added to receive
+  parameters of a queue.
+- The function `new()` passes now a key which is used for the new
+  message queue.
+- A basic test to test the happy path of a queue.
+- The function `get()` to gather facts from a message queue.
+- The function `set()` to set facts of a message queue.
+- The function `create()` to create a message queue.
+- The functions `send()` and `SysvMq::send()` to send messages to a
+  queue.
+- The functions `recv()` and `SysvMq::recv()` to receive messages from
+  a queue.
+- The function `SysvMq::delete()` to delete a queue.
+
 ### Changed
 
+- The function `SysvMq::mode()` now also updates the message queue
+  accordingly.
+- Remove `PhantomData` from the `SysvMq` struct.
+- The function `SysvMq::create()` is replaced by `SysvMq::new()`.
+- Remove generic type for `SysvMq`.
+- Rename `unlink_id()` to `delete()`.
 - Update to the latest verscion of `nix`.
 - Fix several clippy findings in preperation to enable several lint
   groups.
+
+### Removed
+
+- The function `id_from_key()` was removed.

src/lib.rs

@@ -1,24 +1,216 @@
+#![allow(clippy::doc_markdown)]
+//! This library provides a convenient API to SysV IPC message queues.
+//!
+//! # Example
+//!
+//! ```rust
+//! use sysvmq::{SysvMq, SysvMqError};
+//!
+//! fn example() -> Result<(), SysvMqError> {
+//!     let mut mq = SysvMq::new(0)?;
+//!     let mut buf = [0u8; 11];
+//!
+//!     mq.send(b"hello queue")?;
+//!     mq.recv(&mut buf)?;
+//!     mq.delete()?;
+//!
+//!     Ok(())
+//! }
+//! ```
+
 use libc::{
-    msgctl, msgget, msqid_ds, IPC_CREAT, IPC_INFO, IPC_NOWAIT, IPC_RMID, MSG_INFO, MSG_STAT,
+    c_void, msgctl, msgget, msgrcv, msgsnd, msqid_ds, IPC_CREAT, IPC_NOWAIT, IPC_RMID, IPC_SET,
 };
+pub use libc::{IPC_INFO, IPC_STAT, MSG_INFO, MSG_STAT};
 use nix::errno::{errno, Errno};
-use std::{marker::PhantomData, mem::MaybeUninit, ptr};
+use std::{convert::TryFrom, mem::MaybeUninit, ptr};
 use thiserror::Error;
 
 #[derive(Debug, Error)]
+/// An enum containing all errors
 pub enum SysvMqError {
     #[error("SysV message queue: {0}")]
     ErrnoError(&'static str),
+    #[error("Cannot convert integer")]
+    From(#[from] std::num::TryFromIntError),
 }
 
-#[allow(clippy::doc_markdown)]
+/// Low level function to create a new SysV IPC message queue.
-/// Unlink (delete) an existing SysV IPC message queue.
+///
+/// # Example
+///
+/// ```rust
+/// # use sysvmq::delete;
+/// use sysvmq::{create, SysvMqError};
+///
+/// fn main() -> Result<(), SysvMqError> {
+///     let mq_id = create(0, 0o644)?;
+///     println!("new queue: {mq_id}");
+/// #   delete(mq_id)?;
+///
+///     Ok(())
+/// }
+/// ```
 ///
 /// # Errors
 ///
-/// Return an `SysvMqError` when no queue with the given key can be
+/// Return `SysvMqError` when the queue cannot be created.
+pub fn create(key: i32, mode: i32) -> Result<i32, SysvMqError> {
+    let mq = unsafe { msgget(key, IPC_CREAT | mode) };
+
+    match mq {
+        -1 => Err(SysvMqError::ErrnoError(Errno::from_i32(errno()).desc())),
+        id => Ok(id),
+    }
+}
+
+/// Low level function to send a message to a SysV IPC message queue.
+///
+/// # Example
+///
+/// ```rust
+/// # use sysvmq::{delete};
+/// use sysvmq::{create, send, SysvMqError};
+///
+/// fn main() -> Result<(), SysvMqError> {
+///     let mq_id = create(0, 0o644)?;
+///     let msg = b"hello queue";
+///     send(mq_id, msg, 0)?;
+/// #   delete(mq_id)?;
+///
+///     Ok(())
+/// }
+/// ```
+///
+/// # Errors
+///
+/// Return `SysvMqError` when the message cannot be sent to the queue.
+pub fn send(id: i32, msg: &[u8], mask: i32) -> Result<(), SysvMqError> {
+    match unsafe { msgsnd(id, msg.as_ptr().cast::<c_void>(), msg.len(), mask) } {
+        -1 => Err(SysvMqError::ErrnoError(Errno::from_i32(errno()).desc())),
+        _ => Ok(()),
+    }
+}
+
+/// Low level function to receive a message from a SysV IPC message
+/// queue.
+///
+/// # Example
+///
+/// ```rust
+/// # use sysvmq::{delete, send};
+/// use sysvmq::{create, recv, SysvMqError};
+///
+/// fn main() -> Result<(), SysvMqError> {
+///     let mq_mask = 0o644;
+///     let mq_id = create(0, mq_mask)?;
+///     let mut buf = [0u8; 32];
+/// #   let msg = b"hello queue";
+/// #   send(mq_id, msg, 0)?;
+///     recv(mq_id, &mut buf, mq_mask)?;
+///     println!("received message: {:?}", buf);
+/// #   delete(mq_id)?;
+///
+///     Ok(())
+/// }
+/// ```
+///
+/// # Errors
+///
+/// Return `SysvMqError` when the message cannot be received from the
+/// queue.
+pub fn recv(id: i32, msg: &mut [u8], mask: i32) -> Result<(), SysvMqError> {
+    match unsafe { msgrcv(id, msg.as_mut_ptr().cast::<c_void>(), msg.len(), 0, mask) } {
+        -1 => Err(SysvMqError::ErrnoError(Errno::from_i32(errno()).desc())),
+        _ => Ok(()),
+    }
+}
+
+/// Low level function to get parameters of a SysV IPC message queue.
+///
+/// # Example
+///
+/// ```rust
+/// # use sysvmq::{delete};
+/// use sysvmq::{create, get, IPC_STAT, SysvMqError};
+///
+/// fn main() -> Result<(), SysvMqError> {
+///     let mq_id = create(0, 0o644)?;
+///     let mq_stat = get(mq_id, IPC_STAT)?;
+///     println!("received message: {:?}", mq_stat);
+/// #   delete(mq_id)?;
+///
+///     Ok(())
+/// }
+/// ```
+///
+/// # Errors
+///
+/// Return `SysvMqError` when the parameters cannot be gathered.
+pub fn get(id: i32, cmd: i32) -> Result<msqid_ds, SysvMqError> {
+    let mut ipc_info = MaybeUninit::<msqid_ds>::uninit();
+    let ret;
+
+    let ipc_info = unsafe {
+        ret = msgctl(id, cmd, ipc_info.as_mut_ptr());
+        ipc_info.assume_init()
+    };
+
+    match ret {
+        0 => Ok(ipc_info),
+        _ => Err(SysvMqError::ErrnoError(Errno::from_i32(errno()).desc())),
+    }
+}
+
+/// Low level function to set parameters of a SysV IPC message queue.
+///
+/// # Example
+///
+/// ```rust
+/// # use sysvmq::{delete};
+/// use sysvmq::{create, get, IPC_STAT, set, SysvMqError};
+///
+/// fn main() -> Result<(), SysvMqError> {
+///     let mq_id = create(0, 0o644)?;
+///     let mut mq_stat = get(mq_id, IPC_STAT)?;
+///     mq_stat.msg_perm.mode = 0o666;
+///     set(mq_id, &mut mq_stat)?;
+/// #   delete(mq_id)?;
+///
+///     Ok(())
+/// }
+/// ```
+///
+/// # Errors
+///
+/// Return `SysvMqError` when the parameters cannot be set.
+pub fn set(id: i32, data: &mut msqid_ds) -> Result<(), SysvMqError> {
+    match unsafe { msgctl(id, IPC_SET, data) } {
+        0 => Ok(()),
+        _ => Err(SysvMqError::ErrnoError(Errno::from_i32(errno()).desc())),
+    }
+}
+
+/// Low level function to delete a SysV IPC message queue.
+///
+/// # Example
+///
+/// ```rust
+/// use sysvmq::{create, delete, SysvMqError};
+///
+/// fn main() -> Result<(), SysvMqError> {
+///     let mq_id = create(0, 0o644)?;
+///     delete(mq_id)?;
+///
+///     Ok(())
+/// }
+/// ```
+///
+/// # Errors
+///
+/// Return `SysvMqError` when no queue with the given key can be
 /// found.
-pub fn unlink_id(id: i32) -> Result<(), SysvMqError> {
+pub fn delete(id: i32) -> Result<(), SysvMqError> {
     let res = unsafe { msgctl(id, IPC_RMID, ptr::null::<msqid_ds>().cast_mut()) };
 
     match res {
@@ -27,127 +219,137 @@ pub fn unlink_id(id: i32) -> Result<(), SysvMqError> {
     }
 }
 
-#[allow(clippy::doc_markdown)]
+#[derive(Clone, Debug)]
-/// Get the id of an existing SysV IPC message queue by passing its
+/// Struct representation of a Message Queue
+pub struct SysvMq {
+    pub key: i32,
+    pub id: i32,
+    pub mask: i32,
+    pub mode: i32,
+}
+
+impl Default for SysvMq {
+    fn default() -> Self {
+        Self {
+            key: 0,
+            id: -1,
+            mask: 0,
+            mode: 0o644,
+        }
+    }
+}
+
+impl SysvMq {
+    /// Create a new message SysV IPC message queue with the given
     /// key.
     ///
     /// # Errors
     ///
-/// Return an `SysvMqError` when no queue with the given key can be
+    /// Return `SysvMqError` when the queue cannot be created.
-/// found.
+    pub fn new(key: i32) -> Result<Self, SysvMqError> {
-pub fn id_from_key(key: i32) -> Result<i32, SysvMqError> {
+        let mut mq = Self::default();
-    let id = unsafe { msgget(key, 0) };
+        mq.key = key;
-
+        mq.id = create(mq.key, mq.mode)?;
-    match id {
+        Ok(mq)
-        -1 => Err(SysvMqError::ErrnoError(Errno::from_i32(errno()).desc())),
-        id => Ok(id),
-    }
     }
 
-#[allow(clippy::doc_markdown)]
+    /// Open an existing SysV IPC message queye with the given key.
-/// Get the info about an existing SysV IPC message queue.
-pub fn ipc_info(id: i32) {
-    let mut ipc_info = MaybeUninit::<msqid_ds>::uninit();
-
-    let ipc_info = unsafe {
-        msgctl(id, IPC_INFO, ipc_info.as_mut_ptr());
-        ipc_info.assume_init()
-    };
-
-    println!("info: {ipc_info:?}");
-}
-
-#[allow(clippy::doc_markdown)]
-/// Get the stats about an existing SysV IPC message queue.
-pub fn stat_info(id: i32) {
-    let mut stat_info = MaybeUninit::<msqid_ds>::uninit();
-
-    let stat_info = unsafe {
-        msgctl(id, MSG_STAT, stat_info.as_mut_ptr());
-        stat_info.assume_init()
-    };
-
-    println!("info: {stat_info:?}");
-}
-
-#[allow(clippy::doc_markdown)]
-/// Get the message info about an existing SysV IPC message queue.
-pub fn msg_info(id: i32) {
-    let mut msg_info = MaybeUninit::<msqid_ds>::uninit();
-
-    let msg_info = unsafe {
-        msgctl(id, MSG_INFO, msg_info.as_mut_ptr());
-        msg_info.assume_init()
-    };
-
-    println!("info: {msg_info:?}");
-}
-
-pub struct SysvMq<T> {
-    pub id: i32,
-    pub key: i32,
-    message_mask: i32,
-    mode: i32,
-    types: PhantomData<T>,
-}
-
-impl<T> SysvMq<T> {
-    /// Create a new message queye with the given key.
     ///
     /// # Errors
     ///
-    /// Return an `SysvMqError` when no queue with the given key can be
+    /// Return `SysvMqError` when the queue cannot be opened.
-    /// created.
+    pub fn open(key: i32, id: i32) -> Result<Self, SysvMqError> {
-    pub fn create(&mut self, key: i32) -> Result<&Self, SysvMqError> {
+        let mut mq = Self::default();
-        self.key = key;
+        mq.key = key;
-        self.id = unsafe { msgget(self.key, IPC_CREAT | self.mode) };
+        mq.id = id;
-
+        mq.mode = i32::from(get(mq.id, IPC_STAT)?.msg_perm.mode);
-        match self.id {
+        Ok(mq)
-            -1 => Err(SysvMqError::ErrnoError(Errno::from_i32(errno()).desc())),
-            _ => Ok(self),
-        }
     }
 
-    /// Open an existing message queye with the given key.
+    /// Set the mode of a SysV IPC message queue.
     ///
     /// # Errors
     ///
-    /// Return an `SysvMqError` when no queue with the given key can be
+    /// Return `SysvMqError` when the mode of the queue cannot be set.
-    /// found.
+    pub fn mode(&mut self, mode: i32) -> Result<(), SysvMqError> {
-    pub fn open(mut self, key: i32) -> Result<Self, SysvMqError> {
-        self.key = key;
-        self.id = unsafe { msgget(self.key, self.mode) };
-
-        match self.id {
-            -1 => Err(SysvMqError::ErrnoError(Errno::from_i32(errno()).desc())),
-            _ => Ok(self),
-        }
-    }
-
-    pub fn mode(&mut self, mode: i32) -> &Self {
         self.mode = mode;
-        self
+        let mut stats = get(self.id, IPC_STAT)?;
+        stats.msg_perm.mode = u16::try_from(self.mode)?;
+        set(self.id, &mut stats)
     }
 
-    pub fn nonblocking(&mut self) -> &Self {
+    /// Set the mask of a SysV IPC message queue to nonblocking
-        self.message_mask |= IPC_NOWAIT;
+    /// (`IPC_NOWAIT`).
-        self
+    pub fn nonblocking(&mut self) {
+        self.mask |= IPC_NOWAIT;
     }
 
-    #[must_use]
+    /// Send a message to a SysV IPC message queue.
-    pub const fn new() -> Self {
+    ///
-        Self {
+    /// # Errors
-            id: -1,
+    ///
-            key: 0,
+    /// Return `SysvMqError` when the message cannot be sent to the queue.
-            message_mask: 0,
+    pub fn send(&mut self, msg: &[u8]) -> Result<(), SysvMqError> {
-            mode: 0o644,
+        send(self.id, msg, self.mask)
-            types: PhantomData,
-        }
-    }
     }
 
-impl<T> Default for SysvMq<T> {
+    /// Receive a message from a SysV IPC message queue.
-    fn default() -> Self {
+    ///
-        Self::new()
+    /// # Errors
+    ///
+    /// Return `SysvMqError` when the message cannot be received from the
+    /// queue.
+    pub fn recv(&mut self, msg: &mut [u8]) -> Result<(), SysvMqError> {
+        recv(self.id, msg, self.mask)
+    }
+
+    /// Receive stats from a SysV IPC message queue.
+    ///
+    /// # Errors
+    ///
+    /// Return `SysvMqError` when the stats cannot be gathered from
+    /// the queue.
+    pub fn stat(&self) -> Result<msqid_ds, SysvMqError> {
+        get(self.id, IPC_STAT)
+    }
+
+    /// Receive info from a SysV IPC message queue.
+    ///
+    /// # Errors
+    ///
+    /// Return `SysvMqError` when the info cannot be gathered from the
+    /// queue.
+    pub fn info(&self) -> Result<msqid_ds, SysvMqError> {
+        get(self.id, IPC_INFO)
+    }
+
+    /// Receive message stats from a SysV IPC message queue.
+    ///
+    /// # Errors
+    ///
+    /// Return `SysvMqError` when the message stats cannot be gathered
+    /// from the queue.
+    pub fn msg_stat(&self) -> Result<msqid_ds, SysvMqError> {
+        get(self.id, MSG_STAT)
+    }
+
+    /// Receive message info from a SysV IPC message queue.
+    ///
+    /// # Errors
+    ///
+    /// Return `SysvMqError` when the message info cannot be gathered
+    /// from the queue.
+    pub fn msg_info(&self) -> Result<msqid_ds, SysvMqError> {
+        get(self.id, MSG_INFO)
+    }
+
+    /// Delete an existing SysV IPC message queue.
+    ///
+    /// # Errors
+    ///
+    /// Return an `SysvMqError` when no queue with the given key can be
+    /// found.
+    pub fn delete(&mut self) -> Result<(), SysvMqError> {
+        delete(self.id)
     }
 }

tests/main.rs

@@ -0,0 +1,68 @@
+use sysvmq::SysvMq;
+
+#[test]
+fn new_send_recv_delete() {
+    let mut mq = SysvMq::new(0).expect("could not create SysV message queue with key 0");
+    let msg = b"this is a test";
+    let mut buf = [0u8; 14];
+    mq.send(msg)
+        .expect("could not send message to SysV message queue");
+    mq.recv(&mut buf)
+        .expect("could not receive message from SysV message queue");
+    mq.delete().expect("could not destroy SysV message queue");
+    assert_eq!(msg, &buf);
+}
+
+#[test]
+fn separate_send_recv_clone() {
+    let mut sender = SysvMq::new(0).expect("could not create SysV message queue with key 0");
+    let mut receiver = sender.clone();
+    let msg = b"this is another test";
+    let mut buf = [0u8; 20];
+    sender
+        .send(msg)
+        .expect("could not send message to SysV message queue");
+    receiver
+        .recv(&mut buf)
+        .expect("could not receive message from SysV message queue");
+    sender
+        .delete()
+        .expect("could not destroy SysV message queue");
+    assert_eq!(msg, &buf);
+}
+
+#[test]
+fn separate_send_recv_open() {
+    let mut sender = SysvMq::new(0).expect("could not create SysV message queue with key 0");
+    let mut receiver = SysvMq::open(sender.key, sender.id)
+        .expect("could not create second handle to SysV message queue");
+    let msg = b"this is another test";
+    let mut buf = [0u8; 20];
+    sender
+        .send(msg)
+        .expect("could not send message to SysV message queue");
+    receiver
+        .recv(&mut buf)
+        .expect("could not receive message from SysV message queue");
+    sender
+        .delete()
+        .expect("could not destroy SysV message queue");
+    assert_eq!(msg, &buf);
+}
+
+#[test]
+fn change_mode() {
+    let mut mq = SysvMq::new(0).expect("could not create SysV message queue with key 0");
+    let init_stats = mq
+        .stat()
+        .expect("could not get stats from SysV message queue");
+    mq.mode(0o666)
+        .expect("could not set mode of SysV message queue");
+    let new_stats = mq
+        .stat()
+        .expect("could not get stats from SysV message queue");
+    mq.delete().expect("could not destroy SysV message queue");
+
+    assert_eq!(0o644, init_stats.msg_perm.mode);
+    assert_eq!(0o666, new_stats.msg_perm.mode);
+}