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extern crate cursive;
use cursive::{Cursive, Printer};
use cursive::vec::Vec2;
use cursive::traits::*;
use std::sync::mpsc;
use std::thread;
use std::time::Duration;
use std::iter::Chain;
use std::slice::Iter;
fn main() {
// As usual, create the Cursive root
let mut siv = Cursive::new();
// We want to refresh the page even when no input is given.
siv.set_fps(10);
siv.add_global_callback('q', |s| s.quit());
// A channel will communicate data from our running task to the UI.
let (tx, rx) = mpsc::channel();
// Generate data in a separate thread.
thread::spawn(|| {
generate_logs(tx);
});
// And sets the view to read from the other end of the channel.
siv.add_layer(BufferView::new(200, rx).full_screen());
siv.run();
}
// We will only simulate log generation here.
// In real life, this may come from a running task, a separate process, ...
fn generate_logs(tx: mpsc::Sender<String>) {
let mut i = 1;
loop {
let line = format!("Interesting log line {}", i);
i += 1;
// The send will fail when the other side is dropped.
// (When the application ends).
if tx.send(line).is_err() {
return;
}
thread::sleep(Duration::from_millis(30));
}
}
// Let's define a buffer view, that shows the last lines from a stream.
struct BufferView {
// We will emulate a ring buffer
buffer: Vec<String>,
// Current position in the buffer
pos: usize,
// Receiving end of the stream
rx: mpsc::Receiver<String>,
}
impl BufferView {
// Creates a new view with the given buffer size
fn new(size: usize, rx: mpsc::Receiver<String>) -> Self {
BufferView {
rx: rx,
buffer: (0..size).map(|_| String::new()).collect(),
pos: 0,
}
}
// Reads available data from the stream into the buffer
fn update(&mut self) {
let mut i = self.pos;
while let Ok(line) = self.rx.try_recv() {
self.buffer[i] = line;
i = (i + 1) % self.buffer.len();
}
self.pos = i;
}
// Chain together the two parts of the buffer to appear as a circular one.
// TODO: Use `-> impl Iterator<Item=String>`...
fn ring(&self) -> Chain<Iter<String>, Iter<String>> {
// The main buffer is "circular" starting at self.pos
// So we chain the two parts as one
self.buffer[self.pos..].iter().chain(self.buffer[..self.pos].iter())
}
}
impl View for BufferView {
fn layout(&mut self, _: Vec2) {
// Before drawing, we'll want to update the buffer
self.update();
}
fn draw(&self, printer: &Printer) {
// If the buffer is large, we'll discard the beginning and keep the end.
// If the buffer is too small, only print a part of it with an offset.
let (discard, offset) = if self.buffer.len() >
printer.size.y as usize {
(self.buffer.len() - printer.size.y as usize, 0)
} else {
(0, printer.size.y - self.buffer.len())
};
for (i, line) in self.ring().skip(discard).enumerate() {
printer.print((0, offset + i), line);
}
}
}