Supporting Last-Modified Header for StaticFiles

This commit adds basic support of Last-Modified and If-Modified-Since headers
in order to enable HTTP caching while serving static files.

contrib/lib/src/serve.rs

@@ -133,6 +133,12 @@ impl Options {
     /// that would be served is a directory.
     pub const NormalizeDirs: Options = Options(0b0100);
 
+    /// `Options` enabling caching based on the `Last-Modified` header. When
+    /// this is enabled, the [`StaticFiles`] handler will at the `Last-Modified`
+    /// header baesd on the modification datetime of the files in the served
+    /// directory.
+    pub const LastModifiedHeader: Options = Options(0b1000);
+
     /// Returns `true` if `self` is a superset of `other`. In other words,
     /// returns `true` if all of the options in `other` are also in `self`.
     ///
@@ -381,11 +387,19 @@ impl Handler for StaticFiles {
                     return Outcome::forward(data);
                 }
 
-                let index = NamedFile::open(p.join("index.html")).await.ok();
+                let index = named_file(p.join("index.html"), &self.options).await;
                 Outcome::from_or_forward(req, data, index)
             },
-            Some(p) => Outcome::from_or_forward(req, data, NamedFile::open(p).await.ok()),
+            Some(p) => Outcome::from_or_forward(req, data, named_file(p, &self.options).await),
             None => Outcome::forward(data),
         }
     }
 }
+
+async fn named_file<P: AsRef<Path>>(path: P, options: &Options) -> Option<NamedFile> {
+    if options.contains(Options::LastModifiedHeader) {
+        NamedFile::with_last_modified_date(path).await.ok()
+    } else {
+        NamedFile::open(path).await.ok()
+    }
+}

core/lib/Cargo.toml

@@ -45,6 +45,7 @@ indexmap = { version = "1.0", features = ["serde-1"] }
 tempfile = "3"
 async-trait = "0.1.43"
 multer = { version = "2", features = ["tokio-io"] }
+headers = "0.3"
 
 [dependencies.async-stream]
 git = "https://github.com/SergioBenitez/async-stream.git"

core/lib/src/response/named_file.rs

@@ -1,17 +1,24 @@
 use std::io;
-use std::path::{Path, PathBuf};
 use std::ops::{Deref, DerefMut};
+use std::path::{Path, PathBuf};
+use std::time::SystemTime;
 
+use headers::{Header as HeaderTrait, HeaderValue, IfModifiedSince};
 use tokio::fs::File;
 
+use crate::http::{ContentType, Header, Status};
 use crate::request::Request;
 use crate::response::{self, Responder};
-use crate::http::ContentType;
+use crate::Response;
 
 /// A file with an associated name; responds with the Content-Type based on the
 /// file extension.
 #[derive(Debug)]
-pub struct NamedFile(PathBuf, File);
+pub struct NamedFile {
+    path: PathBuf,
+    file: File,
+    modified: Option<SystemTime>,
+}
 
 impl NamedFile {
     /// Attempts to open a file in read-only mode.
@@ -39,7 +46,33 @@ impl NamedFile {
         // all of those `seek`s to determine the file size. But, what happens if
         // the file gets changed between now and then?
         let file = File::open(path.as_ref()).await?;
-        Ok(NamedFile(path.as_ref().to_path_buf(), file))
+        Ok(NamedFile {
+            path: path.as_ref().to_path_buf(),
+            file,
+            modified: None,
+        })
+    }
+
+    /// Attempts to open a file in the same manner as `NamedFile::open` and
+    /// reads the modification timestamp of the file that will be used to
+    /// respond with the `Last-Modified` header. This enables HTTP caching by
+    /// comparing the modification timestamp with the `If-Modified-Since`
+    /// header when requesting the file.
+    ///
+    /// # Examples
+    ///
+    /// ```rust
+    /// use rocket::response::NamedFile;
+    ///
+    /// # #[allow(unused_variables)]
+    /// # rocket::async_test(async {
+    /// let file = NamedFile::with_last_modified_date("foo.txt").await;
+    /// # });
+    /// ```
+    pub async fn with_last_modified_date<P: AsRef<Path>>(path: P) -> io::Result<NamedFile> {
+        let mut named_file = NamedFile::open(path).await?;
+        named_file.modified = named_file.metadata().await?.modified().ok();
+        Ok(named_file)
     }
 
     /// Retrieve the underlying `File`.
@@ -57,7 +90,7 @@ impl NamedFile {
     /// ```
     #[inline(always)]
     pub fn file(&self) -> &File {
-        &self.1
+        &self.file
     }
 
     /// Retrieve a mutable borrow to the underlying `File`.
@@ -75,7 +108,7 @@ impl NamedFile {
     /// ```
     #[inline(always)]
     pub fn file_mut(&mut self) -> &mut File {
-        &mut self.1
+        &mut self.file
     }
 
     /// Take the underlying `File`.
@@ -93,7 +126,7 @@ impl NamedFile {
     /// ```
     #[inline(always)]
     pub fn take_file(self) -> File {
-        self.1
+        self.file
     }
 
     /// Retrieve the path of this file.
@@ -111,7 +144,7 @@ impl NamedFile {
     /// ```
     #[inline(always)]
     pub fn path(&self) -> &Path {
-        self.0.as_path()
+        self.path.as_path()
     }
 }
 
@@ -122,27 +155,50 @@ impl NamedFile {
 /// implied by its extension, use a [`File`] directly.
 impl<'r> Responder<'r, 'static> for NamedFile {
     fn respond_to(self, req: &'r Request<'_>) -> response::Result<'static> {
-        let mut response = self.1.respond_to(req)?;
-        if let Some(ext) = self.0.extension() {
+        if let Some(last_modified) = &self.modified {
+            if let Some(if_modified_since) = req.headers().get_one("If-Modified-Since") {
+                if let Ok(if_modified_since) = parse_if_modified_since(if_modified_since) {
+                    if !if_modified_since.is_modified(*last_modified) {
+                        return Response::build().status(Status::NotModified).ok();
+                    }
+                }
+            }
+        }
+
+        let mut response = self.file.respond_to(req)?;
+        if let Some(ext) = self.path.extension() {
             if let Some(ct) = ContentType::from_extension(&ext.to_string_lossy()) {
                 response.set_header(ct);
             }
         }
 
+        if let Some(last_modified) = self.modified.map(|m| IfModifiedSince::from(m)) {
+            let mut headers = Vec::with_capacity(1);
+            last_modified.encode(&mut headers);
+            let v = headers[0].to_str().unwrap();
+            response.set_header(Header::new("Last-Modified", v.to_string()));
+        }
+
         Ok(response)
     }
 }
 
+fn parse_if_modified_since(header: &str) -> Result<IfModifiedSince, String> {
+    let headers = vec![HeaderValue::from_str(header).map_err(|e| e.to_string())?];
+    let mut headers_it = headers.iter();
+    Ok(IfModifiedSince::decode(&mut headers_it).map_err(|e| e.to_string())?)
+}
+
 impl Deref for NamedFile {
     type Target = File;
 
     fn deref(&self) -> &File {
-        &self.1
+        &self.file
     }
 }
 
 impl DerefMut for NamedFile {
     fn deref_mut(&mut self) -> &mut File {
-        &mut self.1
+        &mut self.file
     }
 }

examples/static-files/src/main.rs

@@ -17,11 +17,17 @@ mod manual {
 
         NamedFile::open(path).await.ok()
     }
+
+    #[rocket::get("/with-caching/rocket-icon.jpg")]
+    pub async fn cached_icon() -> Option<NamedFile> {
+        NamedFile::with_last_modified_date("static/rocket-icon.jpg").await.ok()
+    }
+
 }
 
 #[rocket::launch]
 fn rocket() -> _ {
     rocket::build()
-        .mount("/", rocket::routes![manual::second])
+        .mount("/", rocket::routes![manual::second, manual::cached_icon])
         .mount("/", StaticFiles::from(crate_relative!("static")))
 }

examples/static-files/src/tests.rs

@@ -2,7 +2,7 @@ use std::fs::File;
 use std::io::Read;
 
 use rocket::local::blocking::Client;
-use rocket::http::Status;
+use rocket::http::{Header, Status};
 
 use super::rocket;
 
@@ -25,7 +25,8 @@ fn read_file_content(path: &str) -> Vec<u8> {
     let mut fp = File::open(&path).expect(&format!("Can't open {}", path));
     let mut file_content = vec![];
 
-    fp.read_to_end(&mut file_content).expect(&format!("Reading {} failed.", path));
+    fp.read_to_end(&mut file_content)
+        .expect(&format!("Reading {} failed.", path));
     file_content
 }
 
@@ -69,3 +70,60 @@ fn test_invalid_path() {
     test_query_file("/thou/shalt/not/exist", None, Status::NotFound);
     test_query_file("/thou/shalt/not/exist?a=b&c=d", None, Status::NotFound);
 }
+
+#[test]
+fn test_valid_last_modified() {
+    let client = Client::tracked(rocket()).unwrap();
+    let response = client.get("/with-caching/rocket-icon.jpg").dispatch();
+    assert_eq!(response.status(), Status::Ok);
+
+    let last_modified = response
+        .headers()
+        .get("Last-Modified")
+        .next()
+        .expect("Response should contain Last-Modified header")
+        .to_string();
+
+    let mut request = client.get("/with-caching/rocket-icon.jpg");
+    request.add_header(Header::new("If-Modified-Since".to_string(), last_modified));
+    let response = request.dispatch();
+
+    assert_eq!(response.status(), Status::NotModified);
+}
+
+#[test]
+fn test_none_matching_last_modified() {
+    let client = Client::tracked(rocket()).unwrap();
+
+    let mut request = client.get("/with-caching/rocket-icon.jpg");
+    request.add_header(Header::new(
+        "If-Modified-Since".to_string(),
+        "Wed, 21 Oct 2015 07:28:00 GMT",
+    ));
+    let response = request.dispatch();
+
+    assert_eq!(response.status(), Status::Ok);
+
+    let mut request = client.get("/with-caching/rocket-icon.jpg");
+    request.add_header(Header::new(
+        "If-Modified-Since".to_string(),
+        "Wed, 21 Oct 1900 07:28:00 GMT",
+    ));
+    let response = request.dispatch();
+
+    assert_eq!(response.status(), Status::Ok);
+}
+
+#[test]
+fn test_invalid_last_modified() {
+    let client = Client::tracked(rocket()).unwrap();
+
+    let mut request = client.get("/with-caching/rocket-icon.jpg");
+    request.add_header(Header::new(
+        "If-Modified-Since".to_string(),
+        "random header",
+    ));
+    let response = request.dispatch();
+
+    assert_eq!(response.status(), Status::Ok);
+}