-
-
Notifications
You must be signed in to change notification settings - Fork 26
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
This is not, in the scheme of things, probably a very important or even noticeable contributor to overall performance but it's aesthetically satisfying.
- Loading branch information
Showing
6 changed files
with
124 additions
and
66 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,98 @@ | ||
| // Copyright 2021-2023 Martin Pool | ||
|
|
||
| //! Tail a log file: watch for new writes and return the last line. | ||
| use std::fs::File; | ||
| use std::io::Read; | ||
| use std::path::Path; | ||
|
|
||
| use anyhow::Context; | ||
|
|
||
| use crate::Result; | ||
|
|
||
| #[derive(Debug)] | ||
| pub struct TailFile { | ||
| file: File, | ||
| last_line_seen: String, | ||
| read_buf: Vec<u8>, | ||
| } | ||
|
|
||
| impl TailFile { | ||
| /// Watch the given path. | ||
| pub fn new<P: AsRef<Path>>(path: P) -> Result<Self> { | ||
| let file = File::open(path.as_ref()).context("Open log file")?; | ||
| Ok(TailFile { | ||
| file, | ||
| last_line_seen: String::new(), | ||
| read_buf: Vec::new(), | ||
| }) | ||
| } | ||
|
|
||
| /// Return the last non-empty, non-whitespace line from this file, or an empty string | ||
| /// if none have been seen yet. | ||
| /// | ||
| /// Non-UTF8 content is lost. | ||
| pub fn last_line(&mut self) -> Result<&str> { | ||
| // This assumes that the file always sees writes of whole lines, which seems | ||
| // pretty likely: we don't attempt to stitch up writes of partial lines with | ||
| // later writes, although we could... | ||
| self.read_buf.clear(); | ||
| let n_read = self | ||
| .file | ||
| .read_to_end(&mut self.read_buf) | ||
| .context("Read from log file")?; | ||
| if n_read > 0 { | ||
| if let Some(new_last) = String::from_utf8_lossy(&self.read_buf) | ||
| .lines() | ||
| .filter(|l| !l.trim().is_empty()) | ||
| .last() | ||
| { | ||
| self.last_line_seen = new_last.to_owned(); | ||
| } | ||
| } | ||
| Ok(self.last_line_seen.as_str()) | ||
| } | ||
| } | ||
|
|
||
| #[cfg(test)] | ||
| mod test { | ||
| use camino::Utf8PathBuf; | ||
|
|
||
| use std::io::Write; | ||
|
|
||
| use super::*; | ||
|
|
||
| #[test] | ||
| fn last_line_of_file() { | ||
| let mut tempfile = tempfile::NamedTempFile::new().unwrap(); | ||
| let path: Utf8PathBuf = tempfile.path().to_owned().try_into().unwrap(); | ||
| let mut tailer = TailFile::new(path).unwrap(); | ||
|
|
||
| assert_eq!( | ||
| tailer.last_line().unwrap(), | ||
| "", | ||
| "empty file has an empty last line" | ||
| ); | ||
|
|
||
| tempfile.write_all(b"hello").unwrap(); | ||
| assert_eq!( | ||
| tailer.last_line().unwrap(), | ||
| "hello", | ||
| "single line file with no terminator has that line as last line" | ||
| ); | ||
|
|
||
| tempfile.write_all(b"\n\n\n").unwrap(); | ||
| assert_eq!( | ||
| tailer.last_line().unwrap(), | ||
| "hello", | ||
| "trailing blank lines are ignored" | ||
| ); | ||
|
|
||
| tempfile.write_all(b"that's all folks!\n").unwrap(); | ||
| assert_eq!( | ||
| tailer.last_line().unwrap(), | ||
| "that's all folks!", | ||
| "newline terminated last line is returned" | ||
| ); | ||
| } | ||
| } |