cursive/examples/logs.rs

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Rust
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extern crate cursive;
use std::sync::mpsc;
use std::thread;
use cursive::Cursive;
use cursive::printer::Printer;
use cursive::view::{View,FullView};
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' as i32, |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.
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// (We use FullView to force fullscreen because
// we have no min_size for the BufferView).
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siv.add_layer(FullView::new(BufferView::new(200, rx)));
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;
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// The send will fail when the other side is dropped.
// (When the application ends).
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match tx.send(line) {
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Err(_) => return,
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Ok(_) => (),
}
thread::sleep_ms(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;
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i = (i+1) % self.buffer.len();
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}
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self.pos = i;
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}
// Chain together the two parts of the buffer to appear as a circular one.
// The signature is quite ugly, but basically we return an iterator:
// a Chain of two slice iterators.
fn ring<'a>(&'a self) -> std::iter::Chain<std::slice::Iter<'a,String>, std::slice::Iter<'a,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 draw(&mut self, printer: &Printer, _: bool) {
// Before drawing, we'll want to update the buffer
self.update();
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// If the buffer is large enough, 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)
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} else {
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(0, printer.size.y - self.buffer.len() as u32)
};
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for (i, line) in self.ring().skip(discard).enumerate() {
printer.print((0,offset + i as u32), line);
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}
}
}