X-Git-Url: https://git.ralfj.de/rust-101.git/blobdiff_plain/0223210576f27d0743c2d12b890d30f5c2ef6b2d..2d40516a8393db1f27bb822ff95c71a1a9c82537:/workspace/src/part13.rs
diff --git a/workspace/src/part13.rs b/workspace/src/part13.rs
index 88d1ea6..ae12cd1 100644
--- a/workspace/src/part13.rs
+++ b/workspace/src/part13.rs
@@ -1,107 +1,128 @@
-// Rust-101, Part 13: Slices, Arrays, External Dependencies
-// ========================================================
-
+// Rust-101, Part 13: Concurrency, Arc, Send
+// =========================================
+
+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.
+#[derive(Clone,Copy)]
+pub enum OutputMode {
+ Print,
+ SortAndPrint,
+ Count,
+}
+use self::OutputMode::*;
-// ## Slices
+pub struct Options {
+ pub files: Vec,
+ pub pattern: String,
+ pub output_mode: OutputMode,
+}
-pub fn sort(data: &mut [T]) {
- if data.len() < 2 { return; }
- // We decide that the element at 0 is our pivot, and then we move our cursors through the rest of the slice,
- // making sure that everything on the left is no larger than the pivot, and everything on the right is no smaller.
- let mut lpos = 1;
- let mut rpos = data.len();
- /* Invariant: pivot is data[0]; everything with index (0,lpos) is <= pivot;
- [rpos,len) is >= pivot; lpos < rpos */
- loop {
- // **Exercise 13.1**: Complete this Quicksort loop. You can use `swap` on slices to swap two elements. Write a
- // test function for `sort`.
- unimplemented!()
+// The first function reads the files, and sends every line over the `out_channel`.
+fn read_files(options: Arc, out_channel: SyncSender) {
+ 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();
+ }
}
-
- // Once our cursors met, we need to put the pivot in the right place.
- data.swap(0, lpos-1);
-
- // Finally, we split our slice to sort the two halves. The nice part about slices is that splitting them is cheap:
- let (part1, part2) = data.split_at_mut(lpos);
- unimplemented!()
+ // When we drop the `out_channel`, it will be closed, which the other end can notice.
}
-// **Exercise 13.2**: Since `String` implements `PartialEq`, you can now change the function `output_lines` in the previous part
-// to call the sort function above. If you did exercise 12.1, you will have slightly more work. Make sure you sort by the matched line
-// only, not by filename or line number!
+// 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,
+ in_channel: Receiver,
+ out_channel: SyncSender) {
+ // 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. This is another example of Rust using traits as substitute for overloading.
+ if line.contains(&options.pattern) {
+ unimplemented!()
+ }
+ }
+}
-// Now, we can sort, e.g., an vector of numbers.
-fn sort_nums(data: &mut Vec) {
- sort(&mut data[..]);
+// The third function performs the output operations, receiving the relevant lines on its `in_channel`.
+fn output_lines(options: Arc, in_channel: Receiver) {
+ 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 mut data: Vec = in_channel.iter().collect();
+ // ...and implement the actual sorting later.
+ unimplemented!()
+ }
+ }
}
-// ## Arrays
-fn sort_array() {
- let mut array_of_data: [f64; 5] = [1.0, 3.4, 12.7, -9.12, 0.1];
- sort(&mut array_of_data);
+// With the operations of the three threads defined, we can now implement a function that performs grepping according
+// to some given options.
+pub fn run(options: Options) {
+ // We move the `options` into an `Arc`, as that's what the thread workers expect.
+ let options = Arc::new(options);
+
+ // This sets up the channels. We use a `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();
}
-// ## External Dependencies
-
-
-// I disabled the following module (using a rather bad hack), because it only compiles if `docopt` is linked. However, before enabling it,
-// you still have get the external library into the global namespace. This is done with `extern crate docopt`, and that statement *has* to be
-// in `main.rs`. So please go there, and enable this commented-out line. Then remove the attribute of the `rgrep` module.
-#[cfg(feature = "disabled")]
-pub mod rgrep {
- // Now that `docopt` is linked and declared in `main.rs`, we can import it with `use`. We also import some other pieces that we will need.
- use docopt::Docopt;
- use part12::{run, Options, OutputMode};
- use std::process;
-
- // The `USAGE` string documents how the program is to be called. It's written in a format that `docopt` can parse.
- static USAGE: &'static str = "
-Usage: rgrep [-c] [-s] ...
-
-Options:
- -c, --count Count number of matching lines (rather than printing them).
- -s, --sort Sort the lines before printing.
-";
-
- // This function extracts the rgrep options from the command-line arguments.
- fn get_options() -> Options {
- // Parse `argv` and exit the program with an error message if it fails. This is taken from the [`docopt` documentation](http://burntsushi.net/rustdoc/docopt/).
- let args = Docopt::new(USAGE).and_then(|d| d.parse()).unwrap_or_else(|e| e.exit());
- // Now we can get all the values out.
- let count = args.get_bool("-c");
- let sort = args.get_bool("-s");
- let pattern = args.get_str("");
- let files = args.get_vec("");
- if count && sort {
- println!("Setting both '-c' and '-s' at the same time does not make any sense.");
- process::exit(1);
- }
+// 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);
+}
- // We need to make the strings owned to construct the `Options` instance.
- let mode = if count {
- OutputMode::Count
- } else if sort {
- OutputMode::SortAndPrint
- } else {
- OutputMode::Print
- };
- Options {
- files: files.iter().map(|file| file.to_string()).collect(),
- pattern: pattern.to_string(),
- output_mode: mode,
- }
- }
+// **Exercise 13.1**: Change rgrep such that it prints not 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.
- // Finally, we can call the `run` function from the previous part on the options extracted using `get_options`. Edit `main.rs` to call this function.
- // You can now use `cargo run -- ` to call your program, and see the argument parser and the threads we wrote previously in action!
- pub fn main() {
- unimplemented!()
- }
-}
-// **Exercise 13.3**: Wouldn't it be nice if rgrep supported regular expressions? There's already a crate that does all the parsing and matching on regular
-// expression, it's called [regex](https://crates.io/crates/regex). Add this crate to the dependencies of your workspace, add an option ("-r") to switch
-// the pattern to regular-expression mode, and change `filter_lines` to honor this option. The documentation of regex is available from its crates.io site.
-// (You won't be able to use the `regex!` macro if you are on the stable or beta channel of Rust. But it wouldn't help for our use-case anyway.)