Initial commit

.gitignore

@@ -0,0 +1 @@
+target

Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "turnout-for-what"
+version = "0.1.0"
+authors = ["John Wrenn <[email protected]>"]
+
+[[bin]]
+name = "tfw"

README.rst

@@ -0,0 +1,46 @@
+================
+turnout-for-what
+================
+.. image:: https://upload.wikimedia.org/wikipedia/commons/a/a2/V%C3%BDm%C4%9Bna_hrotit%C3%A1.jpg
+
+Usage
+-----
+::
+
+    tfw SWITCH FILES...
+
+``SWITCH``
+    A file descriptor yielding a stream of line-separated numbers. For every byte received from stdin, the last number received from SWITCH indicates the index of the FILE that the byte should be redirected to.
+
+``FILES``
+    One or more file paths.
+
+Example
+-------
+A load-balancer for the natural numbers::
+
+  #!/usr/bin/env bash
+  i=0;
+  echo "$i" > nat
+  trap "rm nat *.txt" EXIT
+
+  while true; do
+    wc -l *.txt
+    sleep 0.2
+    clear
+  done &
+
+  while true; do
+    sleep 0.2;
+    i=$(expr $i + 1);
+    echo "$i";
+  done \
+    | tee -a nat \
+    | cargo run -- \
+      <(while true; do
+          echo $(expr "$(tail -n 1 nat)" % 5)
+        done) \
+      0.txt 1.txt 2.txt 3.txt 4.txt
+
+This script will create five text files, balance the natural numbers 
+between them, and continuously print their line counts.

src/main.rs

@@ -0,0 +1,58 @@
+use std::io;
+use std::env;
+use std::thread;
+use std::fs::File;
+use std::io::Write;
+use std::sync::Arc;
+use std::io::BufRead;
+use std::io::BufReader;
+use std::fs::OpenOptions;
+use std::sync::atomic::Ordering;
+use std::sync::atomic::AtomicUsize;
+
+fn main() {
+
+  let files = env::args().
+    skip(2).
+    map(|path|
+      OpenOptions::new().
+        read(false).
+        write(true).
+        create(true).
+        open(path)).
+    map(Result::unwrap).
+    collect::<Vec<File>>();
+
+  let target = Arc::new(AtomicUsize::new(0));
+  let target_writer = target.clone();
+
+  thread::spawn(move || {
+    for line in BufReader::new(
+        env::args().nth(1).
+        map(|path|
+          OpenOptions::new().
+            read(true).
+            write(false).
+            create(false).
+            open(path)).
+        unwrap().unwrap()).
+        lines() {
+      target_writer.store(
+        line.unwrap().parse::<usize>().unwrap_or(
+          target_writer.load(Ordering::Relaxed)),
+        Ordering::Relaxed);
+    }
+  });
+
+  let stdin = io::stdin();
+  let mut buffer = stdin.lock();
+
+  loop {
+    let consumed = buffer.fill_buf().
+      map(|bytes| 
+        files.get(target.load(Ordering::Relaxed)).
+      map(|mut file| file.write(bytes))).
+      unwrap().unwrap().unwrap();
+    buffer.consume(consumed);
+  }
+}