Remove extra String alloc improving memory usage

Signed-off-by: Mroik <mroik@delayed.space>

1 files changed, 30 insertions, 32 deletions

diff --git a/src/smtp_server.rs b/src/smtp_server.rs
index 9e313f4..83a1093 100644
--- a/src/smtp_server.rs
+++ b/src/smtp_server.rs
@@ -10,18 +10,18 @@ use tokio::{
 
 use crate::model::Mail;
 
-const SERVER_NAME: &str = "";
-
 pub struct SmtpServer {
     listener: TcpListener,
     running: bool,
+    server_name: String,
 }
 
 impl SmtpServer {
-    pub async fn new(ip: [u8; 4], port: u16) -> Result<Self> {
+    pub async fn new(ip: [u8; 4], port: u16, server_name: &str) -> Result<Self> {
         Ok(Self {
             listener: TcpListener::bind((IpAddr::from(ip), port)).await?,
             running: false,
+            server_name: String::from(server_name),
         })
     }
 
@@ -46,6 +46,7 @@ impl SmtpServer {
             };
             let session = SessionHandler {
                 addr,
+                server_name: self.server_name.clone(),
                 tx_processor: tx_processor.clone(),
                 state: SessionState::default(),
                 client_host: String::new(),
@@ -61,6 +62,7 @@ impl SmtpServer {
 
 struct SessionHandler {
     addr: SocketAddr,
+    server_name: String,
     tx_processor: Sender<Mail>,
     state: SessionState,
     client_host: String,
@@ -76,11 +78,7 @@ impl SessionHandler {
         let mut buffer = String::new();
 
         writer
-            .write_all(
-                Reply::Ready(String::from(SERVER_NAME))
-                    .to_string()
-                    .as_bytes(),
-            )
+            .write_all(Reply::Ready(&self.server_name).to_string().as_bytes())
             .await?;
 
         loop {
@@ -129,7 +127,7 @@ impl SessionHandler {
         Ok(())
     }
 
-    async fn apply(&mut self, command: Command) -> Result<Reply> {
+    async fn apply(&mut self, command: Command<'_>) -> Result<Reply<'_>> {
         match &command {
             Command::HELO(hostname) => self.helo(hostname).await,
             Command::MAIL(from) => self.mail(from).await,
@@ -140,17 +138,17 @@ impl SessionHandler {
     }
 
     /// HELO resets buffers
-    async fn helo(&mut self, hostname: &str) -> Result<Reply> {
+    async fn helo(&mut self, hostname: &str) -> Result<Reply<'_>> {
         self.client_host = String::from(hostname);
         self.state = SessionState::Normal;
         self.from = None;
         self.to.clear();
-        Ok(Reply::Completed(String::from(SERVER_NAME)))
+        Ok(Reply::Completed(&self.server_name))
     }
 
     /// TODO: Validate email address
     /// MAIL resets buffers
-    async fn mail(&mut self, from: &str) -> Result<Reply> {
+    async fn mail(&mut self, from: &str) -> Result<Reply<'_>> {
         if from.is_empty() {
             return Ok(Reply::InvalidParameter);
         }
@@ -159,12 +157,12 @@ impl SessionHandler {
         self.to.clear();
         self.state = SessionState::MailTransaction;
 
-        Ok(Reply::Completed(String::from("Ok")))
+        Ok(Reply::Completed("Ok"))
     }
 
     /// TODO: Validate email addresses
     /// Only after having started a mail transaction
-    async fn rcpt(&mut self, to: &str) -> Result<Reply> {
+    async fn rcpt(&mut self, to: &str) -> Result<Reply<'_>> {
         if self.state != SessionState::MailTransaction {
             return Ok(Reply::BadSequence);
         }
@@ -174,11 +172,11 @@ impl SessionHandler {
         }
 
         self.to.push(String::from(to));
-        Ok(Reply::Completed(String::from("Ok")))
+        Ok(Reply::Completed("Ok"))
     }
 
     /// Only after having started a mail transaction
-    async fn start_data(&mut self) -> std::result::Result<Reply, anyhow::Error> {
+    async fn start_data(&mut self) -> Result<Reply<'_>> {
         if self.state != SessionState::MailTransaction {
             return Ok(Reply::BadSequence);
         }
@@ -193,7 +191,7 @@ impl SessionHandler {
         Ok(Reply::StartMailInput)
     }
 
-    async fn process_mail(&mut self) -> Result<Reply> {
+    async fn process_mail(&mut self) -> Result<Reply<'_>> {
         if self.from.is_none() || self.to.is_empty() || self.data.trim().is_empty() {
             return Ok(Reply::InvalidCommand);
         }
@@ -211,10 +209,10 @@ impl SessionHandler {
         self.to.clear();
         self.data.clear();
 
-        Ok(Reply::Completed(String::from("Ok")))
+        Ok(Reply::Completed("Ok"))
     }
 
-    async fn quit(&self) -> Result<Reply> {
+    async fn quit(&self) -> Result<Reply<'_>> {
         Ok(Reply::EndTransmission)
     }
 }
@@ -229,9 +227,9 @@ enum SessionState {
 }
 
 #[derive(PartialEq)]
-enum Reply {
-    Ready(String),
-    Completed(String),
+enum Reply<'a> {
+    Ready(&'a str),
+    Completed(&'a str),
     StartMailInput,
     InvalidCommand,
     InvalidParameter,
@@ -239,7 +237,7 @@ enum Reply {
     EndTransmission,
 }
 
-impl std::fmt::Display for Reply {
+impl std::fmt::Display for Reply<'_> {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
             Reply::Ready(hostname) => write!(f, "220 {}\r\n", hostname),
@@ -253,20 +251,20 @@ impl std::fmt::Display for Reply {
     }
 }
 
-enum Command {
-    HELO(String),
-    MAIL(String),
-    RCPT(String),
+enum Command<'a> {
+    HELO(&'a str),
+    MAIL(&'a str),
+    RCPT(&'a str),
     DATA,
     QUIT,
 }
 
-impl TryFrom<&str> for Command {
+impl<'a> TryFrom<&'a str> for Command<'a> {
     type Error = anyhow::Error;
 
-    fn try_from(value: &str) -> std::result::Result<Self, Self::Error> {
+    fn try_from(value: &'a str) -> std::result::Result<Self, Self::Error> {
         if value.len() >= 5 && value.to_lowercase().starts_with("helo ") {
-            return Ok(Command::HELO(String::from(&value[5..])));
+            return Ok(Command::HELO(&value[5..]));
         }
 
         if value.len() >= 11
@@ -274,13 +272,13 @@ impl TryFrom<&str> for Command {
             && value.contains('>')
         {
             let from = &value[11..value.find('>').unwrap()];
-            return Ok(Command::MAIL(String::from(from)));
+            return Ok(Command::MAIL(from));
         }
 
         if value.len() >= 9 && value.to_lowercase().starts_with("rcpt to:<") && value.contains('>')
         {
             let to = &value[9..value.find('>').unwrap()];
-            return Ok(Command::RCPT(String::from(to)));
+            return Ok(Command::RCPT(to));
         }
 
         if value.to_lowercase().starts_with("data") {