From e38520f3493a37d500adbca2704e1837bfdc488f Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@gmail.com>
Date: Wed, 17 Jun 2026 11:17:59 +0200
Subject: app: implement simple echo

---
 ttwhy/io.cppm | 84 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 84 insertions(+)
 create mode 100644 ttwhy/io.cppm

(limited to 'ttwhy/io.cppm')

diff --git a/ttwhy/io.cppm b/ttwhy/io.cppm
new file mode 100644
index 0000000..cbd3902
--- /dev/null
+++ b/ttwhy/io.cppm
@@ -0,0 +1,84 @@
+module;
+
+#include <asio.hpp>
+
+#include <expected>
+#include <format>
+#include <string>
+
+export module ttwhy:io;
+
+namespace ttwhy::io
+{
+
+  export template<typename Stream>
+  auto handle_signals(Stream & stream) -> asio::awaitable<std::error_code>
+  {
+    auto executor = co_await asio::this_coro::executor;
+    auto signals = asio::signal_set{executor, SIGINT, SIGTERM};
+
+    auto [error, signal] = co_await signals.async_wait(asio::as_tuple(asio::use_awaitable));
+    if (!error)
+    {
+      auto message = std::format("Received signal {}, exiting ...\n", signal);
+      co_await asio::async_write(stream, asio::buffer(message), asio::use_awaitable);
+    }
+    co_return error;
+  }
+
+  export template<typename InputStream, typename ErrorStream>
+  auto read(InputStream & input_stream, ErrorStream & error_stream)
+      -> asio::awaitable<std::expected<std::string, asio::error_code>>
+  {
+    auto data = std::string{15, '\0'};
+
+    auto [error, read] = co_await input_stream.async_read_some(asio::buffer(data), asio::as_tuple(asio::use_awaitable));
+
+    if (error)
+    {
+      auto message = std::format("{}, exiting ...\n", error.message());
+      co_await asio::async_write(error_stream, asio::buffer(message), asio::use_awaitable);
+      co_return std::unexpected{error};
+    }
+
+    data.resize(read);
+    co_return data;
+  }
+
+  export template<typename OutputStream, typename ErrorStream>
+  auto write(std::string const & string, OutputStream & output_stream, ErrorStream & error_stream)
+      -> asio::awaitable<asio::error_code>
+  {
+    auto [error, written] =
+        co_await asio::async_write(output_stream, asio::buffer(string), asio::as_tuple(asio::use_awaitable));
+
+    if (error)
+    {
+      auto message = std::format("{}, exiting ...\n", error.message());
+      co_await asio::async_write(error_stream, asio::buffer(message), asio::use_awaitable);
+    }
+
+    co_return error;
+  }
+
+  export template<typename InputStream, typename OutputStream, typename ErrorStream>
+  auto echo(InputStream & input_stream, OutputStream & output_stream, ErrorStream & error_stream)
+      -> asio::awaitable<asio::error_code>
+  {
+    while (true)
+    {
+      auto input = co_await read(input_stream, error_stream);
+      if (!input.has_value())
+      {
+        co_return input.error();
+      }
+
+      auto write_error = co_await write(input.value(), output_stream, error_stream);
+      if (write_error)
+      {
+        co_return write_error;
+      }
+    }
+  }
+
+}  // namespace ttwhy::io
-- 
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