micro optimizations (#8)

* perf: break early after parsing required meminfo

Also a match statement for compiler magic.

* perf: pre-allocate strings when reading files

* refactor: remove duplicate .to_string()

* perf: try to print everything in one syscall

println! sends a syscall for each line.

* perf: get rid of duplicate uname syscall

* perf: simplify first letter capitalization

* refactor: directly use key in match statement

src/desktop.rs

@@ -1,21 +1,13 @@
 pub fn get_desktop_info() -> String {
-    fn capitalize_first_letter(s: &str) -> String {
-        if s.is_empty() {
-            return String::new();
-        }
-
-        let mut chars = s.chars();
-        let first_char = chars.next().unwrap().to_uppercase().to_string();
-        let rest: String = chars.collect();
-        first_char + &rest
-    }
-
     // Retrieve the environment variables and handle Result types
     let desktop_env = std::env::var("XDG_CURRENT_DESKTOP");
     let display_backend_result = std::env::var("XDG_SESSION_TYPE");
 
     // Capitalize the first letter of the display backend value
-    let display_backend = capitalize_first_letter(display_backend_result.as_deref().unwrap_or(""));
+    let mut display_backend = display_backend_result.unwrap_or_default();
+    if let Some(c) = display_backend.as_mut_str().get_mut(0..1) {
+        c.make_ascii_uppercase();
+    }
 
     // Trim "none+" from the start of desktop_env if present
     // Use "Unknown" if desktop_env is empty or has an error
@@ -26,10 +18,11 @@ pub fn get_desktop_info() -> String {
 
     // Handle the case where display_backend might be empty after capitalization
     let display_backend = if display_backend.is_empty() {
-        "Unknown".to_string()
+        "Unknown"
     } else {
-        display_backend
-    };
+        &display_backend
+    }
+    .to_string();
 
     format!("{desktop_env} ({display_backend})")
 }

src/main.rs

@@ -4,6 +4,8 @@ mod release;
 mod system;
 mod uptime;
 
+use std::io::Write;
+
 use crate::colors::{print_dots, BLUE, CYAN, RESET};
 use crate::desktop::get_desktop_info;
 use crate::release::{get_os_pretty_name, get_system_info};
@@ -15,10 +17,11 @@ use color_eyre::Report;
 fn main() -> Result<(), Report> {
     color_eyre::install()?;
 
+    let utsname = nix::sys::utsname::uname()?;
     let fields = Fields {
-        user_info: get_username_and_hostname(),
+        user_info: get_username_and_hostname(&utsname),
         os_name: get_os_pretty_name()?,
-        kernel_version: get_system_info()?,
+        kernel_version: get_system_info(&utsname)?,
         shell: get_shell(),
         desktop: get_desktop_info(),
         uptime: get_current()?,
@@ -61,7 +64,7 @@ fn print_system_info(fields: &Fields) {
         colors,
     } = fields;
 
-    println!(
+    let _ = std::io::stdout().write_all(format!(
         "
  {CYAN}     ▟█▖    {BLUE}▝█▙ ▗█▛          {user_info} ~{RESET}
  {CYAN}  ▗▄▄▟██▄▄▄▄▄{BLUE}▝█▙█▛  {CYAN}▖        {CYAN}  {BLUE}System{RESET}        {os_name}
@@ -71,5 +74,6 @@ fn print_system_info(fields: &Fields) {
  {BLUE}   ▟█▛{CYAN}▗█▖       {CYAN}▟█▛          {CYAN}  {BLUE}Desktop{RESET}       {desktop}
  {BLUE}  ▝█▛  {CYAN}██▖{BLUE}▗▄▄▄▄▄▄▄▄▄▄▄       {CYAN}󰍛  {BLUE}Memory{RESET}        {memory_usage}
  {BLUE}   ▝  {CYAN}▟█▜█▖{BLUE}▀▀▀▀▀██▛▀▀▘       {CYAN}󱥎  {BLUE}Storage (/){RESET}   {storage}
- {CYAN}     ▟█▘ ▜█▖    {BLUE}▝█▛          {CYAN}  {BLUE}Colors{RESET}        {colors}");
+ {CYAN}     ▟█▘ ▜█▖    {BLUE}▝█▛          {CYAN}  {BLUE}Colors{RESET}        {colors}
+").as_bytes());
 }

src/release.rs

@@ -1,9 +1,11 @@
 use color_eyre::Result;
-use std::fs::read_to_string;
-use std::io;
+use nix::sys::utsname::UtsName;
+use std::{
+    fs::File,
+    io::{self, Read},
+};
 
-pub fn get_system_info() -> nix::Result<String> {
-    let utsname = nix::sys::utsname::uname()?;
+pub fn get_system_info(utsname: &UtsName) -> nix::Result<String> {
     Ok(format!(
         "{} {} ({})",
         utsname.sysname().to_str().unwrap_or("Unknown"),
@@ -13,15 +15,13 @@ pub fn get_system_info() -> nix::Result<String> {
 }
 
 pub fn get_os_pretty_name() -> Result<String, io::Error> {
-    let os_release_content = read_to_string("/etc/os-release")?;
+    let mut os_release_content = String::with_capacity(1024);
+    File::open("/etc/os-release")?.read_to_string(&mut os_release_content)?;
+
     let pretty_name = os_release_content
         .lines()
         .find(|line| line.starts_with("PRETTY_NAME="))
-        .map(|line| {
-            line.trim_start_matches("PRETTY_NAME=")
-                .trim_matches('"')
-                .to_string()
-        });
+        .map(|line| line.trim_start_matches("PRETTY_NAME=").trim_matches('"'));
 
-    Ok(pretty_name.unwrap_or("Unknown".to_string()))
+    Ok(pretty_name.unwrap_or("Unknown").to_string())
 }

src/system.rs

@@ -1,15 +1,21 @@
 use color_eyre::Result;
-use nix::sys::statvfs::statvfs;
+use nix::sys::{statvfs::statvfs, utsname::UtsName};
 
-use std::env;
-use std::io::{self};
+use std::{
+    env,
+    fs::File,
+    io::{self, Read},
+};
 
 use crate::colors::{CYAN, GREEN, RED, RESET, YELLOW};
 
-pub fn get_username_and_hostname() -> String {
+pub fn get_username_and_hostname(utsname: &UtsName) -> String {
     let username = env::var("USER").unwrap_or("unknown_user".to_string());
-    let hostname = nix::unistd::gethostname().unwrap_or("unknown_host".to_string().into());
-    let hostname = hostname.to_string_lossy();
+    let hostname = utsname
+        .nodename()
+        .to_str()
+        .unwrap_or("unknown_host")
+        .to_string();
 
     format!("{YELLOW}{username}{RED}@{GREEN}{hostname}")
 }
@@ -45,13 +51,20 @@ pub fn get_memory_usage() -> Result<String, io::Error> {
         let mut total_memory_kb = 0.0;
         let mut available_memory_kb = 0.0;
 
-        for line in std::fs::read_to_string("/proc/meminfo")?.lines() {
+        let mut meminfo = String::with_capacity(2048);
+        File::open("/proc/meminfo")?.read_to_string(&mut meminfo)?;
+
+        for line in meminfo.lines() {
             let mut split = line.split_whitespace();
-            let key = split.next().unwrap_or("");
-            if key == "MemTotal:" {
-                total_memory_kb = split.next().unwrap_or("0").parse().unwrap_or(0.0);
-            } else if key == "MemAvailable:" {
+            match split.next().unwrap_or_default() {
+                "MemTotal:" => total_memory_kb = split.next().unwrap_or("0").parse().unwrap_or(0.0),
+                "MemAvailable:" => {
                     available_memory_kb = split.next().unwrap_or("0").parse().unwrap_or(0.0);
+
+                    // MemTotal comes before MemAvailable, stop parsing
+                    break;
+                }
+                _ => (),
             }
         }