add c-ares example

cmake-modules/Findc-ares.cmake

@@ -0,0 +1,61 @@
+#
+# This file is open source software, licensed to you under the terms
+# of the Apache License, Version 2.0 (the "License").  See the NOTICE file
+# distributed with this work for additional information regarding copyright
+# ownership.  You may not use this file except in compliance with the License.
+#
+# You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+#
+
+#
+# Copyright (C) 2018 Scylladb, Ltd.
+#
+
+find_package (PkgConfig REQUIRED)
+
+pkg_check_modules (c-ares_PC libcares)
+
+find_library (c-ares_LIBRARY
+  NAMES cares
+  HINTS
+    ${c-ares_PC_LIBDIR}
+    ${c-ares_PC_LIBRARY_DIRS})
+
+find_path (c-ares_INCLUDE_DIR
+  NAMES ares_dns.h
+  HINTS
+    ${c-ares_PC_INCLUDEDIR}
+    ${c-ares_PC_INCLUDE_DIRS})
+
+mark_as_advanced (
+  c-ares_LIBRARY
+  c-ares_INCLUDE_DIR)
+
+include (FindPackageHandleStandardArgs)
+
+find_package_handle_standard_args (c-ares
+  REQUIRED_VARS
+    c-ares_LIBRARY
+    c-ares_INCLUDE_DIR
+  VERSION_VAR c-ares_PC_VERSION)
+
+set (c-ares_LIBRARIES ${c-ares_LIBRARY})
+set (c-ares_INCLUDE_DIRS ${c-ares_INCLUDE_DIR})
+
+if (c-ares_FOUND AND NOT (TARGET c-ares::cares))
+  add_library (c-ares::cares UNKNOWN IMPORTED)
+
+  set_target_properties (c-ares::cares
+    PROPERTIES
+      IMPORTED_LOCATION ${c-ares_LIBRARY}
+      INTERFACE_INCLUDE_DIRECTORIES ${c-ares_INCLUDE_DIRS})
+endif ()

tests/CMakeLists.txt

@@ -40,3 +40,9 @@ if (LIBEVENT_FOUND)
 endif(LIBEVENT_FOUND)
 
 add_subdirectory(test_executor)
+
+find_package(c-ares)
+
+if(c-ares_FOUND)
+    add_subdirectory(test_cares)
+endif()

tests/test_cares/CMakeLists.txt

@@ -0,0 +1,6 @@
+
+add_executable(testc-ares test.cpp)
+target_link_libraries(testc-ares ucoro c-ares::cares)
+
+add_test(NAME testc-ares COMMAND testc-ares)
+set_target_properties(testc-ares PROPERTIES FOLDER "ucoro_tests")

tests/test_cares/test.cpp

@@ -0,0 +1,155 @@
+#include <iostream>
+#include "ucoro/awaitable.hpp"
+
+#include <ares.h>
+
+
+////////////////////////////////////////////////////////////////////
+
+template <typename ArgType>
+struct __freeer_traits
+{
+    typedef void (*freefunc)(ArgType*);
+};
+
+// NOTE: struct_free 不是一个类型，它就是一个函数本身！
+template<typename StructType, __freeer_traits<StructType>::freefunc struct_free>
+struct raii_c_ptr
+{
+	raii_c_ptr(const raii_c_ptr&) = delete;
+	raii_c_ptr(raii_c_ptr&&) = delete;
+
+	StructType* _managed_resource;
+
+	~raii_c_ptr()
+	{
+        struct_free(_managed_resource);
+	}
+
+	template<typename Initializer>
+	raii_c_ptr(Initializer&& initdata)
+		: _managed_resource(std::forward<Initializer>(initdata))
+	{
+	}
+
+	StructType* operator->()
+	{
+		return _managed_resource;
+	}
+
+	const StructType* operator->() const
+	{
+		return _managed_resource;
+	}
+
+	operator bool() const
+	{
+		return _managed_resource;
+	}
+};
+
+////////////////////////////////////////////////////////////////////
+ucoro::awaitable<std::vector<sockaddr>> aync_cares_query(std::string host)
+{
+	ares_channel_t* channel = co_await ucoro::local_storage_t<ares_channel_t*>();
+
+	ares_addrinfo_hints hints = { 0 };
+
+	/* Perform an IPv4 and IPv6 request for the provided domain name */
+	co_return co_await callback_awaitable<std::vector<sockaddr>>([&](auto continuation_handle) mutable
+	{
+		hints.ai_family = AF_UNSPEC;
+		hints.ai_flags  = ARES_AI_CANONNAME;
+
+		/* Callback that is called when DNS query is finished */
+		auto addrinfo_cb = [](void *arg, int status, int timeouts, struct ares_addrinfo *result_)
+		{
+			// 这里的 magic 是 decltype(continuation_handle) 类型，获取到了 resume 对象的指针.
+			auto continuation_handle_p = reinterpret_cast<decltype(continuation_handle)*>(arg);
+
+			std::vector<sockaddr> ret;
+
+			raii_c_ptr<ares_addrinfo, &ares_freeaddrinfo> result(result_);
+
+			if (result_)
+			{
+				struct ares_addrinfo_node *node;
+				for (node = result->nodes; node != NULL; node = node->ai_next)
+				{
+					ret.push_back(*(node->ai_addr));
+				}
+			}
+
+			(*continuation_handle_p)(ret);
+			delete continuation_handle_p;
+		};
+
+		// continuation_handle 这里被移动构造了一个 堆 上的版本。
+		ares_getaddrinfo(channel, host.c_str(), NULL, &hints, addrinfo_cb, new decltype(continuation_handle){std::move(continuation_handle)});
+	});
+}
+
+
+ucoro::awaitable<void> coro_cares_query()
+{
+	for (auto host : {"microcai.org", "github.com", "google.com", "baidu.com", "boost.org"})
+	{
+		auto dns_result = co_await aync_cares_query(host);
+
+		printf("===================\n");
+		std::cout << "query for \"" << host << "\" result:" << std::endl;
+
+		for (auto sock_address : dns_result)
+		{
+			char        addr_buf[64] = "";
+			const void *ptr          = NULL;
+			if (sock_address.sa_family == AF_INET)
+			{
+				const struct sockaddr_in *in_addr =
+					(const struct sockaddr_in *)((void *) &sock_address);
+				ptr = &in_addr->sin_addr;
+			}
+			else if (sock_address.sa_family == AF_INET6)
+			{
+				const struct sockaddr_in6 *in_addr =
+					(const struct sockaddr_in6 *)((void *) &sock_address);
+				ptr = &in_addr->sin6_addr;
+			}
+			else
+			{
+				continue;
+			}
+			ares_inet_ntop(sock_address.sa_family, ptr, addr_buf, sizeof(addr_buf));
+			printf("Addr: %s\n", addr_buf);
+		}
+	}
+}
+
+int main(int argc, char **argv)
+{
+	ares_library_init(ARES_LIB_INIT_ALL);
+
+	ares_channel_t *channel = NULL;
+  	ares_options options = { 0 };
+
+	/* Enable event thread so we don't have to monitor file descriptors */
+	options.evsys = ARES_EVSYS_DEFAULT;
+
+	/* Initialize channel to run queries, a single channel can accept unlimited
+	* queries */
+	if (ares_init_options(&channel, &options, ARES_OPT_EVENT_THREAD) != ARES_SUCCESS)
+	{
+		printf("c-ares initialization issue\n");
+		return 1;
+	}
+
+	coro_start(coro_cares_query(), channel);
+
+	/* Wait until no more requests are left to be processed */
+	ares_queue_wait_empty(channel, -1);
+
+	/* Cleanup */
+	ares_destroy(channel);
+	ares_library_cleanup();
+	return 0;
+}