Interleaving rw

src/proxy/cache/asio.h

@@ -4,6 +4,9 @@
 #include <concepts>
 #include <entrypoint/http/body.h>
 #include <entrypoint/http/stream.h>
+#include <proxy/cache/awaitable_operators.h>
+
+using namespace boost::asio::experimental::awaitable_operators;
 
 namespace uh::cluster::proxy::cache {
 
@@ -38,8 +41,9 @@ template <BodyType Body> typename Body::writer make_writer(Body& b) {
  *
  * size can be replaced with parser implementation
  */
-template <typename T>
-coro<void> async_read(ep::http::stream& s, T& t, std::size_t size) {
+template <typename S, typename T>
+requires std::is_base_of_v<ep::http::stream, S>
+coro<void> async_read(S& s, T& t, std::size_t size) {
     auto&& reader = [&]() -> auto&& {
         if constexpr (BodyType<T>) {
             return make_reader(t);
@@ -50,6 +54,7 @@ coro<void> async_read(ep::http::stream& s, T& t, std::size_t size) {
                           "T must satisfy BodyType or ReaderBodyType");
         }
     }();
+
     while (size > 0) {
         auto sv = co_await s.read(size);
         if (sv.empty())
@@ -79,11 +84,18 @@ template <typename T> coro<void> async_write(ep::http::stream& s, T& t) {
         }
     }();
 
-    while (true) {
-        std::span<const char> data = co_await writer.get();
-        if (data.empty())
-            break;
-        co_await s.write(data);
+    if constexpr (T::support_double_buffer::value) {
+        for (auto data = co_await writer.get(); !data.empty();) {
+            auto [d, _] = co_await (writer.get() && s.write(data));
+            data = d;
+        }
+    } else {
+        while (true) {
+            auto data = co_await writer.get();
+            if (data.empty())
+                break;
+            co_await s.write(data);
+        }
     }
 }