add veilid flutter plugin skeleton

veilid-flutter/example/windows/runner/utils.cpp

@@ -0,0 +1,64 @@
+#include "utils.h"
+
+#include <flutter_windows.h>
+#include <io.h>
+#include <stdio.h>
+#include <windows.h>
+
+#include <iostream>
+
+void CreateAndAttachConsole() {
+  if (::AllocConsole()) {
+    FILE *unused;
+    if (freopen_s(&unused, "CONOUT$", "w", stdout)) {
+      _dup2(_fileno(stdout), 1);
+    }
+    if (freopen_s(&unused, "CONOUT$", "w", stderr)) {
+      _dup2(_fileno(stdout), 2);
+    }
+    std::ios::sync_with_stdio();
+    FlutterDesktopResyncOutputStreams();
+  }
+}
+
+std::vector<std::string> GetCommandLineArguments() {
+  // Convert the UTF-16 command line arguments to UTF-8 for the Engine to use.
+  int argc;
+  wchar_t** argv = ::CommandLineToArgvW(::GetCommandLineW(), &argc);
+  if (argv == nullptr) {
+    return std::vector<std::string>();
+  }
+
+  std::vector<std::string> command_line_arguments;
+
+  // Skip the first argument as it's the binary name.
+  for (int i = 1; i < argc; i++) {
+    command_line_arguments.push_back(Utf8FromUtf16(argv[i]));
+  }
+
+  ::LocalFree(argv);
+
+  return command_line_arguments;
+}
+
+std::string Utf8FromUtf16(const wchar_t* utf16_string) {
+  if (utf16_string == nullptr) {
+    return std::string();
+  }
+  int target_length = ::WideCharToMultiByte(
+      CP_UTF8, WC_ERR_INVALID_CHARS, utf16_string,
+      -1, nullptr, 0, nullptr, nullptr);
+  if (target_length == 0) {
+    return std::string();
+  }
+  std::string utf8_string;
+  utf8_string.resize(target_length);
+  int converted_length = ::WideCharToMultiByte(
+      CP_UTF8, WC_ERR_INVALID_CHARS, utf16_string,
+      -1, utf8_string.data(),
+      target_length, nullptr, nullptr);
+  if (converted_length == 0) {
+    return std::string();
+  }
+  return utf8_string;
+}