X-Git-Url: https://git.ralfj.de/rust-101.git/blobdiff_plain/bae9e47884fdc3fc1a81fb4844572a832fcfb2ce..c2e9145b487a8bd3d31c5a6f318c86aaf3f9d17d:/workspace/src/part13.rs diff --git a/workspace/src/part13.rs b/workspace/src/part13.rs index 3ef7785..ae12cd1 100644 --- a/workspace/src/part13.rs +++ b/workspace/src/part13.rs @@ -1,96 +1,128 @@ -// Rust-101, Part 13: Slices, Arrays, External Dependencies -// ================= - - -// ## Slices -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. - unimplemented!() - } - - // 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!() +// 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::*; -// **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! - -// Now, we can sort, e.g., an vector of numbers. -fn sort_nums(data: &mut Vec) { - sort(&mut data[..]); +pub struct Options { + pub files: Vec, + pub pattern: String, + pub output_mode: OutputMode, } -// ## Arrays -fn sort_array() { - let mut data: [f64; 5] = [1.0, 3.4, 12.7, -9.12, 0.1]; - sort(&mut data); -} -// ## 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 following 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); +// 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(); } + } + // When we drop the `out_channel`, it will be closed, which the other end can notice. +} - // We need to make the strings owned to construct the `Options` instance. - Options { - files: files.iter().map(|file| file.to_string()).collect(), - pattern: pattern.to_string(), - output_mode: if count { OutputMode::Count } else if sort { OutputMode::SortAndPrint } else { OutputMode::Print }, +// 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!() } } +} - // 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() { - run(get_options()); +// 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!() + } } } -// **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. +// 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(); +} + +// 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 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. + +