WIP: Add new custom event loop for Linux I/O layer

Introduce ev.h and ev.c, establishing the
foundation for the new custom event loop,
`pgagroal_ev`.

Replace previous dependencies on libev with the
custom event loop.

Implement support for io_uring with a fallback to
epoll if io_uring is unavailable.

CMakeLists.txt

@@ -59,11 +59,12 @@ if(NOT COMPILER_SUPPORTS_C17)
   message(FATAL_ERROR "The compiler ${CMAKE_C_COMPILER} has no C17 support. Please use a different C compiler.")
 endif()
 
-find_package(Libev 4.11)
-if (LIBEV_FOUND)
-  message(STATUS "libev found")
-else ()
-  message(FATAL_ERROR "libev needed")
+
+option(HAVE_URING "Use either io_uring or epoll as Linux event handling backend" ON)
+find_package(Liburing 2.5)
+if (NOT LIBURING_FOUND)
+        option(HAVE_URING OFF)
+        message(STATUS "liburing found")
 endif()
 
 find_package(OpenSSL)

cmake/FindLiburing.cmake

@@ -0,0 +1,18 @@
+# - Try to find liburing
+# Once done this will define
+#  LIBURING_FOUND   - System has liburing
+#  LIBURING_LIBRARY - The library needed to use liburing
+
+FIND_LIBRARY(LIBURING_LIBRARY NAMES liburing liburing.a liburing.so liburing.so.2
+        HINTS
+        /usr/lib64
+        /usr/lib
+        /lib64
+        /lib
+)
+
+IF (LIBURING_LIBRARY)
+    SET(LIBURING_FOUND TRUE)
+ELSE ()
+        SET(LIBURING_FOUND FALSE)
+ENDIF ()

scripts/build.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+build_dir=$(pwd)/build
+mkdir -p $build_dir
+cd $build_dir
+rm -rf *
+cmake -S .. -G "Unix Makefiles" -B . -DCMAKE_BUILD_TYPE=Debug
+make
+rm ../compile_commands.json
+ln -s $build_dir/compile_commands.json ..

src/CMakeLists.txt

@@ -19,7 +19,6 @@ if (${CMAKE_SYSTEM_NAME} STREQUAL "Linux")
   #
   include_directories(
     ${CMAKE_CURRENT_SOURCE_DIR}/include
-    ${LIBEV_INCLUDE_DIRS}
     ${OPENSSL_INCLUDE_DIR}
     ${SYSTEMD_INCLUDE_DIRS}
     ${CJSON_INCLUDE_DIRS}
@@ -29,14 +28,26 @@ if (${CMAKE_SYSTEM_NAME} STREQUAL "Linux")
   # Library directories
   #
   link_libraries(
-    ${LIBEV_LIBRARIES}
     ${OPENSSL_CRYPTO_LIBRARY}
     ${OPENSSL_SSL_LIBRARY}
     ${SYSTEMD_LIBRARIES}
     ${LIBATOMIC_LIBRARY}
     ${CJSON_LIBRARIES}
   )
 
+  #
+  # Event library backend
+  #
+  if (HAVE_URING)
+    add_compile_options(-DHAVE_URING=1)
+    include_directories(${LIBURING_INCLUDE_DIRS})
+    link_libraries(${LIBURING_LIBRARY})
+    message(STATUS "pgagroal ev handling backend: io_uring")
+  else ()
+    add_compile_options(-DHAVE_URING=0)
+    message(STATUS "pgagroal ev handling backend: epoll")
+  endif()
+
   set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,--no-undefined")
 elseif(${CMAKE_SYSTEM_NAME} STREQUAL "Darwin")
   find_program(HOMEBREW_EXECUTABLE brew)