Refactor AuthFileReader to use iterator pattern for reading lines

Author: FastAlien

src/auth_file_reader.rs

@@ -4,15 +4,13 @@ use std::io::{BufRead, BufReader, Seek, SeekFrom};
 
 pub struct AuthFileReader {
     reader: BufReader<File>,
-    file_content_buffer: String,
 }
 
 impl AuthFileReader {
-    pub fn new(filepath: &str, buffer_size: usize) -> Result<AuthFileReader, Box<dyn Error>> {
+    pub fn new(filepath: &str) -> Result<AuthFileReader, Box<dyn Error>> {
         let file = File::open(filepath)?;
         return Ok(AuthFileReader {
             reader: BufReader::new(file),
-            file_content_buffer: String::with_capacity(buffer_size),
         });
     }
 
@@ -21,31 +19,24 @@ impl AuthFileReader {
         return Ok(());
     }
 
-    pub fn read_new_lines(&mut self, mut parse_line: impl FnMut(&String)) {
-        loop {
-            self.file_content_buffer.clear();
-            let bytes_read = self
-                .reader
-                .read_line(&mut self.file_content_buffer)
-                .unwrap_or_else(|error| {
-                    eprintln!("Error reading file: {}", error);
-                    return 0;
-                });
-            if bytes_read > 0 {
-                parse_line(&self.file_content_buffer);
-                continue;
-            }
-            if !self.is_file_has_been_truncated() {
-                break;
-            }
+    pub fn next_line(&mut self) -> Option<String> {
+        let mut line = String::new();
+        let _ = self.reader.read_line(&mut line).unwrap_or_else(|error| {
+            eprintln!("Error reading file: {}", error);
+            return 0;
+        });
+        if !line.is_empty() {
+            return Some(line);
+        }
+        if self.is_file_has_been_truncated() {
             match self.reader.seek(SeekFrom::Start(0)) {
                 Ok(position) => println!("Resetting position in file to {}", position),
                 Err(error) => {
                     eprintln!("Error resetting position in file: {}", error);
-                    break;
                 }
             }
         }
+        return None;
     }
 
     fn is_file_has_been_truncated(&self) -> bool {

src/auth_file_watcher.rs

@@ -8,7 +8,6 @@ use crate::file_event_filter::{FileAction, FileEventFilter};
 use crate::file_path::FilePath;
 
 const EVENT_BUFFER_SIZE: usize = 1024;
-const READER_BUFFER_SIZE: usize = 1024;
 
 pub struct AuthFileWatcher {
     filepath: String,
@@ -48,7 +47,7 @@ impl AuthFileWatcher {
     }
 
     fn open_file(&mut self) {
-        let reader = match AuthFileReader::new(&self.filepath, READER_BUFFER_SIZE) {
+        let reader = match AuthFileReader::new(&self.filepath) {
             Ok(reader) => reader,
             Err(error) => {
                 eprintln!("Unable to open monitored file: {}", error);
@@ -70,7 +69,10 @@ impl AuthFileWatcher {
         self.reader = Some(reader);
     }
 
-    pub fn update(&mut self, parse_line: impl FnMut(&String)) {
+    pub fn update<F>(&mut self, mut parse_line: F)
+    where
+        F: FnMut(&String),
+    {
         let events = match self.inotify.read_events(&mut self.event_buffer) {
             Ok(events) => events,
             Err(error) => {
@@ -111,7 +113,9 @@ impl AuthFileWatcher {
         }
 
         if let Some(reader) = &mut self.reader {
-            reader.read_new_lines(parse_line);
+            while let Some(line) = reader.next_line() {
+                parse_line(&line);
+            }
         };
     }