Add a base class for http async clients; refine examples.

example/http_ssl_async_client/CMakeLists.txt

@@ -0,0 +1,11 @@
+add_executable(http_ssl_async_client main.cc)
+
+# TODO
+set(SSL_LIBS ${OPENSSL_LIBRARIES})
+if(WIN32)
+	set(SSL_LIBS ${SSL_LIBS} crypt32)
+endif()
+
+target_link_libraries(http_ssl_async_client webcc ${Boost_LIBRARIES})
+target_link_libraries(http_ssl_async_client "${CMAKE_THREAD_LIBS_INIT}")
+target_link_libraries(http_ssl_async_client ${SSL_LIBS})

example/http_ssl_async_client/main.cc

@@ -0,0 +1,58 @@
+#include <iostream>
+
+#include "boost/asio/io_context.hpp"
+
+#include "webcc/http_ssl_async_client.h"
+#include "webcc/logger.h"
+
+int main(int argc, char* argv[]) {
+  std::string host;
+  std::string url;
+
+  if (argc != 3) {
+    host = "www.boost.org";
+    url = "/LICENSE_1_0.txt";
+  } else {
+    host = argv[1];
+    url = argv[2];
+  }
+
+  std::cout << "Host: " << host << std::endl;
+  std::cout << "URL:  " << url << std::endl;
+  std::cout << std::endl;
+
+  WEBCC_LOG_INIT("", webcc::LOG_CONSOLE);
+
+  boost::asio::io_context io_context;
+
+  // Leave port to default value.
+  auto request = webcc::HttpRequest::Make(webcc::kHttpGet, url, host);
+
+  // Verify the certificate of the peer or not.
+  // See HttpSslClient::Request() for more details.
+  bool ssl_verify = false;
+
+  webcc::HttpSslAsyncClientPtr client{
+    new webcc::HttpSslAsyncClient{ io_context, 2000, ssl_verify }
+  };
+
+  // Response callback.
+  auto callback = [](webcc::HttpResponsePtr response, webcc::Error error,
+                     bool timed_out) {
+    if (error == webcc::kNoError) {
+      std::cout << response->content() << std::endl;
+    } else {
+      std::cout << DescribeError(error);
+      if (timed_out) {
+        std::cout << " (timed out)";
+      }
+      std::cout << std::endl;
+    }
+  };
+
+  client->Request(request, callback);
+
+  io_context.run();
+
+  return 0;
+}