Support unicode characters in model path (#3681)

* parse wide argv characters on windows

* cleanup

* move cleanup to end of `main`

llm/ext_server/server.cpp

@@ -39,6 +39,10 @@
 #include "httplib.h"
 #include "json.hpp"
 
+#if defined(_WIN32)
+#include <windows.h>
+#endif
+
 #include <cstddef>
 #include <thread>
 #include <chrono>
@@ -2770,8 +2774,28 @@ inline void signal_handler(int signal) {
     shutdown_handler(signal);
 }
 
-int main(int argc, char **argv)
-{
+#if defined(_WIN32)
+char* wchar_to_char(const wchar_t* wstr) {
+    if (wstr == nullptr) return nullptr;
+
+    // Determine the number of bytes needed for the UTF-8 string
+    int bytes = WideCharToMultiByte(CP_UTF8, 0, wstr, -1, nullptr, 0, nullptr, nullptr);
+    char* str = new char[bytes];
+
+    // Convert the wide-character string to a UTF-8 string
+    WideCharToMultiByte(CP_UTF8, 0, wstr, -1, str, bytes, nullptr, nullptr);
+    return str;
+}
+
+int wmain(int argc, wchar_t **wargv) {
+    char** argv = new char*[argc];
+    for (int i = 0; i < argc; ++i) {
+        argv[i] = wchar_to_char(wargv[i]);
+    }
+#else
+int main(int argc, char **argv) {
+#endif
+
 #if SERVER_VERBOSE != 1
     log_disable();
 #endif
@@ -3282,6 +3306,11 @@ int main(int argc, char **argv)
         return (ctrl_type == CTRL_C_EVENT) ? (signal_handler(SIGINT), true) : false;
     };
     SetConsoleCtrlHandler(reinterpret_cast<PHANDLER_ROUTINE>(console_ctrl_handler), true);
+
+    for (int i = 0; i < argc; ++i) {
+        delete[] argv[i];
+    }
+    delete[] argv;
 #endif
     llama.queue_tasks.start_loop();
     svr.stop();