--- /dev/null
+// Rust-101, Part 12: Concurrency (WIP)
+// =================
+
+use std::io::prelude::*;
+use std::{io, fs, thread};
+use std::sync::mpsc::{sync_channel, SyncSender, Receiver};
+use std::sync::Arc;
+
+
+// Before we come to the actual code, we define a data-structure `Options` to store all the information we need
+// to complete the job: Which files to work on, which pattern to look for, and how to output. <br/>
+// Besides just printing all the matching lines, we will also offer to count them, or alternatively to sort them.
+#[derive(Clone,Copy)]
+enum OutputMode {
+ Print,
+ SortAndPrint,
+ Count,
+}
+use self::OutputMode::*;
+
+struct Options {
+ files: Vec<String>,
+ pattern: String,
+ output_mode: OutputMode,
+}
+
+
+// The first functions reads the files, and sends every line over the `out_channel`.
+fn read_files(options: Arc<Options>, out_channel: SyncSender<String>) {
+ for file in options.files.iter() {
+ // First, we open the file, ignoring any errors.
+ let file = fs::File::open(file).unwrap();
+ // Then we obtain a `BufReader` for it, which provides the `lines` function.
+ let file = io::BufReader::new(file);
+ for line in file.lines() {
+ let line = line.unwrap();
+ // Now we send the line over the channel, ignoring the possibility of `send` failing.
+ out_channel.send(line).unwrap();
+ }
+ }
+ // When we drop the `out_channel`, it will be closed, which the other end can notice.
+}
+
+// The second function filters the lines it receives through `in_channel` with the pattern, and sends
+// matches via `out_channel`.
+fn filter_lines(options: Arc<Options>, in_channel: Receiver<String>, out_channel: SyncSender<String>) {
+ // We can simply iterate over the channel, which will stop when the channel is closed.
+ for line in in_channel.iter() {
+ // `contains` works on lots of types of patterns, but in particular, we can use it to test whether
+ // one string is contained in another.
+ if line.contains(&options.pattern) {
+ unimplemented!()
+ }
+ }
+}
+
+// The third function performs the output operations, receiving the relevant lines on its `in_channel`.
+fn output_lines(options: Arc<Options>, in_channel: Receiver<String>) {
+ match options.output_mode {
+ Print => {
+ // Here, we just print every line we see.
+ for line in in_channel.iter() {
+ unimplemented!()
+ }
+ },
+ Count => {
+ // We are supposed to count the number of matching lines. There's a convenient iterator adapter that
+ // we can use for this job.
+ unimplemented!()
+ },
+ SortAndPrint => {
+ // We are asked to sort the matching lines before printing. So let's collect them all in a local vector...
+ let data: Vec<String> = in_channel.iter().collect();
+ // ...and implement the actual sorting later.
+ unimplemented!()
+ }
+ }
+}
+
+// With the operations of the three threads defined, we can now implement a function that performs grepping according
+// to some given options.
+fn run(options: Options) {
+ // We move the `options` into an `Arc`, as that's what the thread workers expect.
+ let options = Arc::new(options);
+
+ // Set up the channels. Use `sync_channel` with buffer-size of 16 to avoid needlessly filling RAM.
+ let (line_sender, line_receiver) = sync_channel(16);
+ let (filtered_sender, filtered_receiver) = sync_channel(16);
+
+ // Spawn the read thread: `thread::spawn` takes a closure that is run in a new thread.
+ let options1 = options.clone();
+ let handle1 = thread::spawn(move || read_files(options1, line_sender));
+
+ // Same with the filter thread.
+ let options2 = options.clone();
+ let handle2 = thread::spawn(move || filter_lines(options2, line_receiver, filtered_sender));
+
+ // And the output thread.
+ let options3 = options.clone();
+ let handle3 = thread::spawn(move || output_lines(options3, filtered_receiver));
+
+ // Finally, wait until all three threads did their job.
+ handle1.join().unwrap();
+ handle2.join().unwrap();
+ handle3.join().unwrap();
+}
+
+// Now we have all the pieces together for testing our `rgrep` with some hard-coded options.
+pub fn main() {
+ let options = Options {
+ files: vec!["src/part10.rs".to_string(), "src/part11.rs".to_string(), "src/part12.rs".to_string()],
+ pattern: "let".to_string(),
+ output_mode: Print
+ };
+ run(options);
+}
+
+// **Exercise 12.1**: Change `rgrep` such that it prints now only the matching lines, but also the name of the file
+// and the number of the line in the file. You will have to change the type of the channels from `String` to something
+// that records this extra information.
+
+
+
projects / rust-101.git / blobdiff