libos: Add basic IPC message framework

libos/CMakeLists.txt

@@ -16,6 +16,7 @@ set(SOURCES
     src/Security.cpp
     src/LocalServer.cpp
     src/LocalClient.cpp
+    src/IPC.cpp
 )
 
 add_library(os ${SOURCES})

libos/include/os/IPC.h

@@ -0,0 +1,157 @@
+/**
+ * @file IPC.h
+ * @author apio (cloudapio.eu)
+ * @brief Inter-process communication primitives.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#pragma once
+#include <os/LocalClient.h>
+#include <os/LocalServer.h>
+
+#define IPC_ENUM_SERVER(name) __##name##_SERVER_ERROR = 0
+#define IPC_ENUM_CLIENT(name) __##name##_CLIENT_ERROR = 0
+
+/**
+ * @brief Called to handle IPC events (client-side).
+ *
+ * @param conn The connection object being used.
+ * @param id The ID of the message.
+ * @return Result<void> Whether the operation succeded.
+ */
+extern Result<void> handle_ipc_client_event(os::LocalClient& conn, u8 id);
+
+/**
+ * @brief Called to handle IPC events (server-side).
+ *
+ * @param conn The connection object being used.
+ * @param id The ID of the message.
+ * @return Result<void> Whether the operation succeded.
+ */
+extern Result<void> handle_ipc_server_event(os::LocalServer::Client& conn, u8 id);
+
+namespace os
+{
+    namespace IPC
+    {
+        static constexpr usize IPC_STRING_LENGTH = 256;
+
+#define IPC_STRING(name) char name[os::IPC::IPC_STRING_LENGTH];
+#define COPY_IPC_STRING(name)                                                                                          \
+    TRY(String::from_string_view(StringView::from_fixed_size_cstring(name, os::IPC::IPC_STRING_LENGTH)))
+#define SET_IPC_STRING(name, value) strlcpy(name, value, os::IPC::IPC_STRING_LENGTH)
+
+        /**
+         * @brief Sends an IPC message without waiting for a reply.
+         *
+         * @tparam Client The type of the client interface being used to communicate.
+         * @tparam T The type of the message.
+         * @param client The connection object being used to communicate.
+         * @param message The IPC message.
+         * @return Result<void> Whether the operation succeded.
+         */
+        template <typename Client, typename T> Result<void> send_async(Client& client, const T& message)
+        {
+            u8 id = T::id;
+            TRY(client.send_typed(id));
+            TRY(client.send_typed(message));
+            return {};
+        }
+
+        /**
+         * @brief Sends an error result to the IPC connection, indicating that an operation could not be performed.
+         *
+         * @tparam Client The type of the client interface being used to communicate.
+         * @param client The connection object being used to communicate.
+         * @param error The error code.
+         * @return Result<void> Whether the operation succeded.
+         */
+        template <typename Client> Result<void> send_error(Client& client, int error)
+        {
+            u8 id = 0;
+            TRY(client.send_typed(id));
+            TRY(client.send_typed(error));
+            return {};
+        }
+
+        /**
+         * @brief Sends an IPC message and waits for a reply (client-only).
+         *
+         * @tparam ResponseType The type of the response.
+         * @tparam T The type of the message.
+         * @param client The connection object being used to communicate.
+         * @param message The IPC message.
+         * @param handler The function used to handle messages that do not match the reply.
+         * @return Result<ResponseType> An error, or the response.
+         */
+        template <typename ResponseType, typename T>
+        Result<ResponseType> send_sync(os::LocalClient& client, const T& message,
+                                       decltype(handle_ipc_client_event) handler = handle_ipc_client_event)
+        {
+            u8 id = T::id;
+            TRY(client.send_typed(id));
+            TRY(client.send_typed(message));
+
+            // We allow receiving 5 messages of different types, but if those have passed and we still don't have a
+            // reply, fail with ENOMSG.
+            int max_other_messages = 5;
+
+            while (max_other_messages)
+            {
+                u8 response_id;
+                auto rc = client.recv_typed(response_id);
+                if (rc.has_error() && rc.error() == EAGAIN) continue;
+
+                if (response_id == 0) // Error result
+                {
+                    while (1)
+                    {
+                        int code;
+                        rc = client.recv_typed(code);
+                        if (rc.has_error() && rc.error() == EAGAIN) continue;
+                        return err(code);
+                    }
+                }
+
+                if (response_id != ResponseType::id)
+                {
+                    TRY(handler(client, response_id));
+                    max_other_messages--;
+                    continue;
+                }
+
+                while (1)
+                {
+                    ResponseType response;
+                    rc = client.recv_typed(response);
+                    if (rc.has_error() && rc.error() == EAGAIN) continue;
+                    return response;
+                }
+            }
+
+            return err(ENOMSG);
+        }
+
+        /**
+         * @brief Check for new IPC messages on a connection and handle them appropriately.
+         *
+         * @param client The client connection.
+         * @param handler The function used to handle messages.
+         * @return Result<void> Whether the operation succeded.
+         */
+        Result<void> check_for_messages(os::LocalClient& client,
+                                        decltype(handle_ipc_client_event) handler = handle_ipc_client_event);
+
+        /**
+         * @brief Check for new IPC messages on a connection and handle them appropriately.
+         *
+         * @param server The server connection.
+         * @param handler The function used to handle messages.
+         * @return Result<void> Whether the operation succeded.
+         */
+        Result<void> check_for_messages(os::LocalServer::Client& server,
+                                        decltype(handle_ipc_server_event) handler = handle_ipc_server_event);
+    }
+}

libos/src/IPC.cpp

@@ -0,0 +1,39 @@
+/**
+ * @file IPC.cpp
+ * @author apio (cloudapio.eu)
+ * @brief Inter-process communication primitives.
+ *
+ * @copyright Copyright (c) 2023, the Luna authors.
+ *
+ */
+
+#include <os/IPC.h>
+
+namespace os::IPC
+{
+    Result<void> check_for_messages(os::LocalClient& client, decltype(handle_ipc_client_event) handler)
+    {
+        u8 id;
+        auto rc = client.recv_typed(id);
+        if (rc.has_error())
+        {
+            if (rc.error() == EAGAIN) return {}; // No messages, and the caller does not want us to block.
+            return rc.release_error();
+        }
+
+        return handler(client, id);
+    }
+
+    Result<void> check_for_messages(os::LocalServer::Client& client, decltype(handle_ipc_server_event) handler)
+    {
+        u8 id;
+        auto rc = client.recv_typed(id);
+        if (rc.has_error())
+        {
+            if (rc.error() == EAGAIN) return {}; // No messages, and the caller does not want us to block.
+            return rc.release_error();
+        }
+
+        return handler(client, id);
+    }
+}