Move to the new std::io APIs for parsing proc files

The implementation is certainly not cleaner to look at.  For whatever
reason, the noticeable delay that was present on startup previously
is now gone, so some performance issue must have been resolved with
this change as well.

pstree.rs

@@ -27,14 +27,15 @@
 // of different items, notably the process name and its parent process id (ppid).
 // And with that information, we can build the process tree.
 
-#![feature(old_io)]
-#![feature(old_path)]
 #![feature(std_misc)] // hash_map::Entry
+#![feature(path)]
+#![feature(fs)]
+#![feature(io)]
 
-use std::old_io::fs::PathExtensions;
-use std::old_io::fs;
-use std::old_io::File;
-use std::old_io::BufferedReader;
+use std::path::Path;
+use std::fs;
+use std::io::prelude::*;
+use std::fs::File;
 use std::collections::hash_map::Entry::{Occupied, Vacant};
 use std::collections::HashMap;
 
@@ -71,10 +72,15 @@ fn get_process_record(status_path: &Path) -> Option<ProcessRecord> {
     let mut ppid : Option<i32> = None;
     let mut name : Option<String> = None;
 
-    let mut status_file = BufferedReader::new(File::open(status_path));
-    for line in status_file.lines() {
-        let unwrapped = line.unwrap(); // need a new lifeline
-        let parts : Vec<&str> = unwrapped[..].splitn(2, ':').collect();
+    let mut reader = std::io::BufReader::new(File::open(status_path).unwrap());
+    loop {
+        let mut linebuf = String::new();
+        match reader.read_line(&mut linebuf) {
+            Ok(_) => {
+                if linebuf.is_empty() {
+                    break;
+                }
+                let parts : Vec<&str> = linebuf[..].splitn(2, ':').collect();
                 if parts.len() == 2 {
                     let key = parts[0].trim();
                     let value = parts[1].trim();
@@ -85,8 +91,10 @@ fn get_process_record(status_path: &Path) -> Option<ProcessRecord> {
                         _ => (),
                     }
                 }
+            },
+            Err(_) => break,
+        }
     }
-
     return if pid.is_some() && ppid.is_some() && name.is_some() {
         Some(ProcessRecord { name: name.unwrap(), pid: pid.unwrap(), ppid: ppid.unwrap() })
     } else {
@@ -100,10 +108,11 @@ fn get_process_records() -> Vec<ProcessRecord> {
     let proc_directory = Path::new("/proc");
 
     // find potential process directories under /proc
-    let proc_directory_contents = fs::readdir(&proc_directory).unwrap();
-    proc_directory_contents.iter().filter_map(|entry| {
-        if entry.is_dir() {
-            let status_path = entry.join("status");
+    let proc_directory_contents = fs::read_dir(&proc_directory).unwrap();
+    proc_directory_contents.filter_map(|entry| {
+        let entry_path = entry.unwrap().path();
+        if entry_path.is_dir() {
+            let status_path = entry_path.join("status");
             if status_path.exists() {
                 return get_process_record(&status_path)
             }