stream books instead of reading them into memory

Cargo.lock

@@ -1371,6 +1371,7 @@ dependencies = [
  "thiserror",
  "time",
  "tokio",
+ "tokio-util",
  "tracing",
  "tracing-subscriber",
  "uuid",

rusty-library/Cargo.toml

@@ -17,6 +17,7 @@ tera = "1.19.1"
 thiserror = { workspace = true }
 time = { workspace = true }
 tokio = { version = "1.37.0", features = ["rt-multi-thread", "macros"] }
+tokio-util = "0.7.11"
 tracing = "0.1.40"
 tracing-subscriber = "0.3.18"
 uuid = { version = "1.8.0", features = ["v4", "fast-rng"] }

rusty-library/src/handlers/download.rs

@@ -1,18 +1,22 @@
 //! Handle requests for specific formats of a book.
 
-use std::{fs::File, io::Read, sync::Arc};
+use std::sync::Arc;
+
+use tokio::fs::File;
 
 use poem::{
     error::NotFoundError,
     handler,
-    web::{Data, Path, WithContentType, WithHeader},
-    IntoResponse,
+    web::{Data, Path},
+    Body, IntoResponse, Response,
 };
+use tokio_util::io::ReaderStream;
 
 use crate::{
     app_state::AppState,
     data::book::{Book, Format},
     handlers::error::HandlerError,
+    opds::media_type::MediaType,
 };
 
 /// Handle a request for a book with id `id` in format `format`.
@@ -20,7 +24,7 @@ use crate::{
 pub async fn handler(
     Path((id, format)): Path<(u64, String)>,
     state: Data<&Arc<AppState>>,
-) -> Result<WithHeader<WithContentType<Vec<u8>>>, poem::Error> {
+) -> Result<Response, poem::Error> {
     let book = state
         .calibre
         .scalar_book(id)
@@ -33,13 +37,14 @@ pub async fn handler(
         .library_path
         .join(book.data.path)
         .join(file_name);
-    let mut file = File::open(file_path).map_err(|_| NotFoundError)?;
 
-    let mut data = Vec::new();
-    file.read_to_end(&mut data).map_err(|_| NotFoundError)?;
-    let content_type = format.0;
+    let mut file = File::open(file_path).await.map_err(|_| NotFoundError)?;
+    let stream = ReaderStream::new(file);
+    let body = Body::from_bytes_stream(stream);
 
-    Ok(data
-        .with_content_type(content_type)
-        .with_header("Content-Disposition", format!("filename={file_name};")))
+    let content_type: MediaType = format.into();
+    Ok(body
+        .with_content_type(format!("{content_type}"))
+        .with_header("Content-Disposition", format!("filename=\"{file_name}\""))
+        .into_response())
 }