Reduce allocations when fetching headers.

Author: alistairjevans

ext/hyper_ruby/src/gvl_helpers.rs

@@ -2,6 +2,7 @@ use std::{ffi::c_void, mem::MaybeUninit, ptr::null_mut};
 use rb_sys::rb_thread_call_without_gvl;
 
 // Call a specified function, having released the GVL. Acquires the GVL before returning.
+// Credit to https://github.com/Shopify/lz4-flex-rb for this one.
 pub(crate) fn nogvl<F, R>(mut func: F) -> R
 where
     F: FnMut() -> R,

ext/hyper_ruby/src/request.rs

@@ -18,8 +18,10 @@ impl Request {
         RString::new(&self.request.uri().path())
     }
 
-    pub fn header(&self, key: String) -> Value {
-        match self.request.headers().get(key) {
+    pub fn header(&self, key: RString) -> Value {
+        // Avoid allocating a new header key string
+        let key_str = unsafe { key.as_str().unwrap() };
+        match self.request.headers().get(key_str) {
             Some(value) => match value.to_str() {
                 Ok(value) => RString::new(value).as_value(),
                 Err(_) => qnil().as_value(),

test/test_hyper_ruby.rb

@@ -17,6 +17,14 @@ def test_simple_get
     end
   end
 
+  def test_header_fetch_get
+    with_server(-> (request) { handler_return_header(request, 'User-Agent') }) do |client|
+      response = client.get("/", headers: { 'User-Agent' => 'test' })
+      assert_equal 200, response.status
+      assert_equal "test", JSON.parse(response.body)["message"]
+    end
+  end
+
   def test_simple_post
     with_server(-> (request) { handler_to_json(request) }) do |client|
       response = client.post("/", body: "Hello")
@@ -113,4 +121,9 @@ def handler_simple(request)
   def handler_to_json(request)
     HyperRuby::Response.new(200, { 'Content-Type' => 'application/json' }, { message: request.body }.to_json)
   end
+  
+
+  def handler_return_header(request, header_key)
+    HyperRuby::Response.new(200, { 'Content-Type' => 'application/json' }, { message: request.header(header_key) }.to_json)
+  end
 end