Receive message(s) from a queue

This subcommand receives one or more messages from a queue. Three
different methods are supported, read message by message, read until a
given timout or read until a specified date and time. This subcommand
also supports the `--non-blocking` flag.

Cargo.lock

@@ -29,6 +29,19 @@ version = "1.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cf1de2fe8c75bc145a2f577add951f8134889b4795d47466a54a5c846d691693"
 
+[[package]]
+name = "chrono"
+version = "0.4.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "670ad68c9088c2a963aaa298cb369688cf3f9465ce5e2d4ca10e6e0098a1ce73"
+dependencies = [
+ "libc",
+ "num-integer",
+ "num-traits",
+ "time",
+ "winapi",
+]
+
 [[package]]
 name = "clap"
 version = "3.0.0-beta.2"
@@ -112,10 +125,30 @@ name = "mqrs"
 version = "0.1.0-dev"
 dependencies = [
  "anyhow",
+ "chrono",
  "clap",
  "posixmq",
 ]
 
+[[package]]
+name = "num-integer"
+version = "0.1.44"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d2cc698a63b549a70bc047073d2949cce27cd1c7b0a4a862d08a8031bc2801db"
+dependencies = [
+ "autocfg",
+ "num-traits",
+]
+
+[[package]]
+name = "num-traits"
+version = "0.2.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9a64b1ec5cda2586e284722486d802acf1f7dbdc623e2bfc57e65ca1cd099290"
+dependencies = [
+ "autocfg",
+]
+
 [[package]]
 name = "os_str_bytes"
 version = "2.4.0"
@@ -208,6 +241,17 @@ dependencies = [
  "unicode-width",
 ]
 
+[[package]]
+name = "time"
+version = "0.1.44"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6db9e6914ab8b1ae1c260a4ae7a49b6c5611b40328a735b21862567685e73255"
+dependencies = [
+ "libc",
+ "wasi",
+ "winapi",
+]
+
 [[package]]
 name = "unicode-segmentation"
 version = "1.7.1"
@@ -238,6 +282,12 @@ version = "0.9.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5fecdca9a5291cc2b8dcf7dc02453fee791a280f3743cb0905f8822ae463b3fe"
 
+[[package]]
+name = "wasi"
+version = "0.10.0+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1a143597ca7c7793eff794def352d41792a93c481eb1042423ff7ff72ba2c31f"
+
 [[package]]
 name = "winapi"
 version = "0.3.9"

Cargo.toml

@@ -11,3 +11,4 @@ description = "A CLI program for interacting Posix Message Queues"
 anyhow = "1.0"
 clap = "3.0.0-beta.2"
 posixmq = "1.0"
+chrono = "0.4"

src/cli.rs

@@ -1,4 +1,4 @@
-use crate::{create::Create, info::Info, send::Send, unlink::Unlink};
+use crate::{create::Create, info::Info, recv::Recv, send::Send, unlink::Unlink};
 use clap::{crate_authors, crate_version, AppSettings, Clap};
 
 #[derive(Clap, Debug)]
@@ -23,4 +23,5 @@ pub enum Command {
     Info(Info),
     Unlink(Unlink),
     Send(Send),
+    Recv(Recv),
 }

src/main.rs

@@ -4,6 +4,7 @@ use clap::Clap;
 mod cli;
 mod create;
 mod info;
+mod recv;
 mod send;
 mod unlink;
 
@@ -17,6 +18,7 @@ fn main() -> Result<()> {
         Command::Info(i) => i.run()?,
         Command::Unlink(u) => u.run(opts.verbose)?,
         Command::Send(s) => s.run(opts.verbose)?,
+        Command::Recv(r) => r.run(opts.verbose)?,
     }
 
     Ok(())

src/recv.rs

@@ -0,0 +1,92 @@
+use anyhow::Result;
+use chrono::{DateTime, Local};
+use clap::Clap;
+use posixmq::PosixMq;
+use std::{str, time::Duration};
+
+/// Receive and print a message from a message queue
+#[derive(Clap, Debug)]
+pub struct Recv {
+    /// Do not block
+    #[clap(short, long)]
+    pub non_blocking: bool,
+    /// Print messages as they are received
+    #[clap(short, long)]
+    pub follow: bool,
+    /// Print a timestamp before each message
+    #[clap(short, long)]
+    pub timestamp: bool,
+    /// Timeout in "<timeout>[s]" (default) or "<timeout>ms"
+    #[clap(short = 'o', long)]
+    pub timeout: Option<String>,
+    /// Deadline until messages are received (format: "%Y-%m-%d %H:%M:%S")
+    #[clap(short, long)]
+    pub deadline: Option<String>,
+    #[clap(value_name = "QNAME")]
+    pub queue: String,
+}
+
+fn print_message(verbose: bool, priority: u32, length: usize, timestamp: bool, msg: &str) {
+    if verbose {
+        println!("Priority: {}, length: {}", priority, length);
+    }
+
+    if timestamp {
+        println!("{}", Local::now());
+    }
+
+    println!("{}", msg);
+}
+
+impl Recv {
+    fn receive(&self, verbose: bool, mq: &PosixMq) -> Result<()> {
+        let mut buf = vec![0; mq.attributes()?.max_msg_len];
+
+        if let Some(timeout) = &self.timeout {
+            let timeout = if timeout.ends_with("ms") {
+                Duration::from_millis(timeout[0..timeout.len() - 2].parse::<u64>()?)
+            } else if timeout.ends_with("s") {
+                Duration::from_secs(timeout[0..timeout.len() - 1].parse::<u64>()?)
+            } else {
+                Duration::from_secs(timeout.parse::<u64>()?)
+            };
+
+            let (prio, len) = mq.recv_timeout(&mut buf, timeout)?;
+
+            print_message(verbose, prio, len, self.timestamp, str::from_utf8(&buf)?);
+        } else if let Some(deadline) = &self.deadline {
+            let (prio, len) = mq.recv_deadline(
+                &mut buf,
+                DateTime::parse_from_str(deadline, "%Y-%m-%d %H:%M:%S")?.into(),
+            )?;
+
+            print_message(verbose, prio, len, self.timestamp, str::from_utf8(&buf)?);
+        } else {
+            let (prio, len) = mq.recv(&mut buf)?;
+
+            print_message(verbose, prio, len, self.timestamp, str::from_utf8(&buf)?);
+        }
+
+        Ok(())
+    }
+
+    pub fn run(&self, verbose: bool) -> Result<()> {
+        let mq = &mut posixmq::OpenOptions::readonly();
+
+        if self.non_blocking {
+            mq.nonblocking();
+        }
+
+        let mq = mq.open(&self.queue)?;
+
+        if self.follow {
+            loop {
+                self.receive(verbose, &mq)?;
+            }
+        } else {
+            self.receive(verbose, &mq)?;
+        }
+
+        Ok(())
+    }
+}