compress wasm file

Author: jakobhellermann

Cargo.toml

@@ -21,3 +21,4 @@ tokio = { version = "1.11", default-features = false, features = ["rt-multi-thre
 tower-http = { version = "0.2", features = ["fs", "trace"] }
 tower = "0.4"
 fastrand = "1.5"
+flate2 = "1.0"

src/main.rs

@@ -30,7 +30,7 @@ fn main() -> Result<(), anyhow::Error> {
 
     let output = wasm_bindgen::generate(&wasm_file)?;
 
-    info!("wasm output is {} large", pretty_size(output.wasm.len()));
+    info!("wasm output is {} large", pretty_size(output.compressed_wasm.len()));
 
     let rt = tokio::runtime::Runtime::new()?;
     rt.block_on(server::run_server(options, output))?;

src/server.rs

@@ -1,7 +1,7 @@
 use std::net::SocketAddr;
 
 use axum::http::{HeaderValue, StatusCode};
-use axum::response::{Html, IntoResponse, Response};
+use axum::response::{Headers, Html, IntoResponse, Response};
 use axum::routing::{get, get_service};
 use axum::Router;
 use tower::ServiceBuilder;
@@ -19,7 +19,7 @@ pub struct Options {
 }
 
 pub async fn run_server(options: Options, output: WasmBindgenOutput) -> Result<()> {
-    let WasmBindgenOutput { js, wasm } = output;
+    let WasmBindgenOutput { js, compressed_wasm } = output;
 
     let middleware_stack = ServiceBuilder::new().into_inner();
 
@@ -29,10 +29,16 @@ pub async fn run_server(options: Options, output: WasmBindgenOutput) -> Result<(
 
     let serve_dir = get_service(ServeDir::new(".")).handle_error(internal_server_error);
 
+    let serve_wasm = || async move {
+        let headers = Headers(std::iter::once(("Content-Encoding", "gzip")));
+        let response = WithContentType("application/wasm", compressed_wasm);
+        (headers, response)
+    };
+
     let app = Router::new()
         .route("/", get(move || async { Html(html) }))
         .route("/api/wasm.js", get(|| async { WithContentType("application/javascript", js) }))
-        .route("/api/wasm.wasm", get(|| async { WithContentType("application/wasm", wasm) }))
+        .route("/api/wasm.wasm", get(serve_wasm))
         .route("/api/version", get(move || async { version }))
         .fallback(serve_dir)
         .layer(middleware_stack);

src/wasm_bindgen.rs

@@ -1,10 +1,14 @@
 use std::path::Path;
 
+use anyhow::Context;
+
 use crate::Result;
 
+const COMPRESSION_LEVEL: u32 = 2;
+
 pub struct WasmBindgenOutput {
     pub js: String,
-    pub wasm: Vec<u8>,
+    pub compressed_wasm: Vec<u8>,
 }
 pub fn generate(wasm_file: &Path) -> Result<WasmBindgenOutput> {
     let mut output = wasm_bindgen_cli_support::Bindgen::new()
@@ -13,8 +17,23 @@ pub fn generate(wasm_file: &Path) -> Result<WasmBindgenOutput> {
         .typescript(false)
         .generate_output()?;
 
-    Ok(WasmBindgenOutput {
-        js: output.js().to_owned(),
-        wasm: output.wasm_mut().emit_wasm(),
-    })
+    let js = output.js().to_owned();
+    let wasm = output.wasm_mut().emit_wasm();
+
+    let compressed_wasm = compress(&wasm).context("failed to compress wasm file")?;
+
+    Ok(WasmBindgenOutput { js, compressed_wasm })
+}
+
+fn compress(bytes: &[u8]) -> Result<Vec<u8>, std::io::Error> {
+    use flate2::write::GzEncoder;
+    use flate2::Compression;
+    use std::io::prelude::*;
+
+    let mut encoder = GzEncoder::new(Vec::new(), Compression::new(COMPRESSION_LEVEL));
+
+    encoder.write_all(bytes)?;
+    let compressed = encoder.finish()?;
+
+    Ok(compressed)
 }