Prevent cloning paste on show where not necessary

Author: w4

Cargo.lock

@@ -8,9 +8,10 @@ authors = ["Jordan Doyle <jordan@doyle.la>"]
 edition = "2018"
 
 [dependencies]
+owning_ref = "0.4"
 linked-hash-map = "0.5"
 rocket = { version = "0.4", default-features = false }
-askama = "0.7"
+askama = "0.8"
 lazy_static = "1.2"
 rand = { version = "0.6", features = ["nightly"] }
 gpw = "0.1"

Cargo.toml

@@ -1,15 +1,18 @@
 extern crate gpw;
 extern crate linked_hash_map;
+extern crate owning_ref;
 extern crate rand;
 
 use rand::distributions::Alphanumeric;
 use rand::{thread_rng, Rng};
 
 use linked_hash_map::LinkedHashMap;
 
+use owning_ref::RwLockReadGuardRef;
+
 use std::cell::RefCell;
 use std::env;
-use std::sync::RwLock;
+use std::sync::{PoisonError, RwLock};
 
 lazy_static! {
     static ref ENTRIES: RwLock<LinkedHashMap<String, String>> = RwLock::new(LinkedHashMap::new());
@@ -25,12 +28,12 @@ lazy_static! {
 ///
 /// During the purge, `ENTRIES` is locked and the current thread will block.
 fn purge_old() {
-    let entries_len = ENTRIES.read().unwrap_or_else(|p| p.into_inner()).len();
+    let entries_len = ENTRIES.read().unwrap_or_else(PoisonError::into_inner).len();
 
     if entries_len > *BUFFER_SIZE {
         let to_remove = entries_len - *BUFFER_SIZE;
 
-        let mut entries = ENTRIES.write().unwrap_or_else(|p| p.into_inner());
+        let mut entries = ENTRIES.write().unwrap_or_else(PoisonError::into_inner);
 
         for _ in 0..to_remove {
             entries.pop_front();
@@ -54,17 +57,19 @@ pub fn store_paste(id: String, content: String) {
     purge_old();
     ENTRIES
         .write()
-        .unwrap_or_else(|p| p.into_inner())
+        .unwrap_or_else(PoisonError::into_inner)
         .insert(id, content);
 }
 
 /// Get a paste by id.
 ///
 /// Returns `None` if the paste doesn't exist.
-pub fn get_paste(id: &str) -> Option<String> {
-    ENTRIES
-        .read()
-        .unwrap_or_else(|p| p.into_inner())
-        .get(id)
-        .cloned()
+pub fn get_paste(id: &str) -> Option<RwLockReadGuardRef<LinkedHashMap<String, String>, String>> {
+    let or = RwLockReadGuardRef::new(ENTRIES.read().unwrap_or_else(PoisonError::into_inner));
+
+    if or.contains_key(id) {
+        Some(or.map(|x| x.get(id).unwrap()))
+    } else {
+        None
+    }
 }

src/io.rs

@@ -17,14 +17,15 @@ use highlight::highlight;
 use io::{generate_id, get_paste, store_paste};
 use params::{HostHeader, IsPlaintextRequest};
 
-use askama::{MarkupDisplay, Template};
+use askama::{Html as AskamaHtml, MarkupDisplay, Template};
 
 use rocket::http::{ContentType, Status};
 use rocket::request::Form;
 use rocket::response::content::{Content, Html};
 use rocket::response::Redirect;
 use rocket::Data;
 
+use std::borrow::Cow;
 use std::io::Read;
 
 ///
@@ -39,7 +40,7 @@ struct Index;
 fn index() -> Result<Html<String>, Status> {
     Index
         .render()
-        .map(|h| Html(h))
+        .map(Html)
         .map_err(|_| Status::InternalServerError)
 }
 
@@ -82,8 +83,8 @@ fn submit_raw(input: Data, host: HostHeader) -> std::io::Result<String> {
 
 #[derive(Template)]
 #[template(path = "paste.html")]
-struct ShowPaste {
-    content: MarkupDisplay<String>,
+struct ShowPaste<'a> {
+    content: MarkupDisplay<AskamaHtml, Cow<'a, String>>,
 }
 
 #[get("/<key>")]
@@ -94,22 +95,24 @@ fn show_paste(key: String, plaintext: IsPlaintextRequest) -> Result<Content<Stri
 
     // get() returns a read-only lock, we're not going to be writing to this key
     // again so we can hold this for as long as we want
-    let entry = get_paste(key).ok_or_else(|| Status::NotFound)?;
+    let entry = &*get_paste(key).ok_or_else(|| Status::NotFound)?;
 
     if *plaintext {
-        Ok(Content(ContentType::Plain, entry))
+        Ok(Content(ContentType::Plain, entry.to_string()))
     } else {
         let content = match ext {
-            None => MarkupDisplay::Unsafe(entry),
-            Some(extension) => highlight(&entry, extension)
-                .map(|h| MarkupDisplay::Safe(h))
-                .ok_or_else(|| Status::NotFound)?,
+            Some(extension) => match highlight(&entry, extension) {
+                Some(html) => MarkupDisplay::new_safe(Cow::Owned(html), AskamaHtml),
+                None => return Err(Status::NotFound),
+            },
+            None => MarkupDisplay::new_unsafe(Cow::Borrowed(entry), AskamaHtml),
         };
 
-        ShowPaste { content }
-            .render()
-            .map(|html| Content(ContentType::HTML, html))
-            .map_err(|_| Status::InternalServerError)
+        let template = ShowPaste { content };
+        match template.render() {
+            Ok(html) => Ok(Content(ContentType::HTML, html)),
+            Err(_) => Err(Status::InternalServerError),
+        }
     }
 }