ZacharyZhang-NY
b7fca0146d
ElyDoc, ElyTable, ElyShow (LibreOfficeKit), ElyPDF (MuPDF), ElyTree (Git), ElyMark (Milkdown and CodeMirror in CEF). ElyMail and ElyAgent follow.
99 lines
3.1 KiB
Rust
99 lines
3.1 KiB
Rust
use std::{
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fs::{self, File, OpenOptions},
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io::{self, Write},
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panic,
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path::{Path, PathBuf},
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sync::OnceLock,
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};
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use anyhow::{Context, Result};
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use env_logger::{Builder, Env, Target};
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use crate::{AppId, data_dir};
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static LOG_PATH: OnceLock<PathBuf> = OnceLock::new();
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struct Tee(File);
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impl Write for Tee {
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fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
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self.0.write_all(buf)?;
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io::stderr().write_all(buf)?;
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Ok(buf.len())
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}
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fn flush(&mut self) -> io::Result<()> {
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self.0.flush()?;
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io::stderr().flush()
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}
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}
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/// The file logging writes to; none until `init` succeeds.
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pub fn path() -> Option<&'static Path> {
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LOG_PATH.get().map(PathBuf::as_path)
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}
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/// Past this a log keeps only its newer half (§18.3).
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const LOG_CAP: u64 = 8 * 1024 * 1024;
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/// Keeps a long log's newer half, from a whole line.
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fn trimmed(path: &Path, cap: u64) -> std::io::Result<()> {
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let length = match fs::metadata(path) {
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Ok(meta) => meta.len(),
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Err(error) if error.kind() == std::io::ErrorKind::NotFound => return Ok(()),
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Err(error) => return Err(error),
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};
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if length <= cap {
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return Ok(());
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}
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let bytes = fs::read(path)?;
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let tail = &bytes[(length - cap / 2) as usize..];
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let whole = tail.iter().position(|b| *b == b'\n').map_or(tail.len(), |n| n + 1);
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fs::write(path, &tail[whole..])
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}
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/// Logs to stderr and a file. `ELY_LOG` sets level.
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pub fn init(app: AppId) -> Result<()> {
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init_in(app, &data_dir(app)?)
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}
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pub fn init_in(app: AppId, dir: &Path) -> Result<()> {
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fs::create_dir_all(dir).with_context(|| format!("cannot create {}", dir.display()))?;
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let path = dir.join("ely.log");
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trimmed(&path, LOG_CAP).with_context(|| format!("cannot trim {}", path.display()))?;
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let file = OpenOptions::new()
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.create(true)
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.append(true)
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.open(&path)
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.with_context(|| format!("cannot open {}", path.display()))?;
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Builder::from_env(Env::new().filter_or("ELY_LOG", "info"))
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.target(Target::Pipe(Box::new(Tee(file))))
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.try_init()
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.context("a logger is already set")?;
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LOG_PATH.set(path).expect("the logger was set once");
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let previous = panic::take_hook();
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panic::set_hook(Box::new(move |info| {
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log::error!("panic: {info}");
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previous(info);
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}));
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log::info!("{} {} started", app.name(), env!("CARGO_PKG_VERSION"));
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Ok(())
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}
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#[cfg(test)]
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mod trim_tests {
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#[test]
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fn a_long_log_keeps_its_newer_half_from_a_line() {
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let dir = tempfile::tempdir().unwrap();
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let path = dir.path().join("ely.log");
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let lines: String = (0..200).map(|n| format!("line {n:03}\n")).collect();
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std::fs::write(&path, &lines).unwrap();
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super::trimmed(&path, 1000).unwrap();
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let kept = std::fs::read_to_string(&path).unwrap();
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assert!(kept.len() <= 500 && kept.starts_with("line ") && kept.ends_with("line 199\n"), "{kept}");
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super::trimmed(&path, 1000).unwrap();
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assert_eq!(std::fs::read_to_string(&path).unwrap(), kept, "a short log stays");
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}
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}
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