Add lock while downloading cacert.pem to avoid conflicting

Author: stdrc

src/cqhttp/plugins/web/websocket_reverse.cpp

@@ -6,6 +6,7 @@
 #include "cqhttp/core/core.h"
 #include "cqhttp/core/helpers.h"
 #include "cqhttp/utils/http.h"
+#include "cqhttp/utils/mutex.h"
 
 using namespace std;
 namespace fs = std::filesystem;
@@ -14,6 +15,7 @@ namespace cqhttp::plugins {
     static const auto TAG = "反向WS";
 
     using utils::http::download_file;
+    using utils::mutex::with_file_lock;
     using helpers::get_asset_url;
 
     static string check_ws_url(const string &url) {
@@ -27,12 +29,19 @@ namespace cqhttp::plugins {
             auto ok = true;
 
             if (!fs::exists(ansi(cacert_file))) {
-                logging::info(
-                    TAG, u8"正在下载 CA 证书文件，这只会在第一次启动时进行，如果耗时较长，请在配置文件中更换更新源");
-                if (download_file(get_asset_url("cacert.pem"), cacert_file, true)) {
-                    logging::info_success(TAG, u8"下载 CA 证书文件成功");
-                } else {
-                    logging::warning(TAG, u8"下载 CA 证书文件失败，可能导致无法 WSS");
+                try {
+                    with_file_lock(cq::dir::app("tmp") + "~cacert.pem", [&] {
+                        logging::info(
+                            TAG,
+                            u8"正在下载 CA 证书文件，这只会在第一次启动时进行，如果耗时较长，请在配置文件中更换更新源");
+                        if (download_file(get_asset_url("cacert.pem"), cacert_file, true)) {
+                            logging::info_success(TAG, u8"下载 CA 证书文件成功");
+                        } else {
+                            logging::warning(TAG, u8"下载 CA 证书文件失败，可能导致无法 WSS");
+                            ok = false;
+                        }
+                    });
+                } catch (runtime_error &) {
                     ok = false;
                 }
             }

src/cqhttp/utils/mutex.cpp

@@ -0,0 +1,28 @@
+#include "./mutex.h"
+
+#include <filesystem>
+#include <fstream>
+
+using namespace std;
+namespace fs = std::filesystem;
+
+namespace cqhttp::utils::mutex {
+    static bool acquire(string ansi_file_path) {
+        ofstream f(ansi_file_path);
+        return f.is_open();
+    }
+
+    void with_file_lock(string file_path, const function<void()> func) {
+        const auto ansi_file_path = ansi(file_path);
+        while (fs::exists(ansi_file_path)) {
+            this_thread::sleep_for(50ms);
+        }
+
+        if (acquire(ansi_file_path)) {
+            func();
+            fs::remove(ansi_file_path);
+        } else {
+            throw runtime_error("failed to acquire file lock");
+        }
+    }
+} // namespace cqhttp::utils::mutex

src/cqhttp/utils/mutex.h

@@ -9,4 +9,6 @@ namespace cqhttp::utils::mutex {
         std::unique_lock<std::mutex> lock(m);
         func();
     }
+
+    void with_file_lock(std::string file_path, const std::function<void()> func);
 } // namespace cqhttp::utils::mutex