Add a wrapper for the main function on Windows

A macro and forward declaration are added to compat.h that rename
the main() function programs using compat.h into sqfs_tools_main.

An actual main() function is added to libcompat.a, that uses the
shell API to get the UTF-16 command line arguments, convert them
to UTF-8 and call sqfs_tools_main.

Signed-off-by: David Oberhollenzer <david.oberhollenzer@sigma-star.at>

3 files changed, 89 insertions, 0 deletions

diff --git a/include/compat.h b/include/compat.h
index e82f2ad..59133c9 100644
--- a/include/compat.h
+++ b/include/compat.h
@@ -227,4 +227,10 @@ WCHAR *path_to_windows(const char *input);
 int fnmatch(const char *, const char *, int);
 #endif
 
+#if defined(_WIN32) || defined(__WINDOWS__)
+#define main sqfs_tools_main
+
+extern int sqfs_tools_main(int argc, char **argv);
+#endif
+
 #endif /* COMPAT_H */
diff --git a/lib/compat/Makemodule.am b/lib/compat/Makemodule.am
index 6ea0750..f9dce2e 100644
--- a/lib/compat/Makemodule.am
+++ b/lib/compat/Makemodule.am
@@ -3,6 +3,7 @@ libcompat_a_SOURCES += lib/compat/strndup.c lib/compat/mockups.c
 libcompat_a_SOURCES += lib/compat/chdir.c include/compat.h
 libcompat_a_SOURCES += lib/compat/path_to_windows.c
 libcompat_a_SOURCES += lib/compat/w32_perror.c
+libcompat_a_SOURCES += lib/compat/w32_wmain.c
 libcompat_a_SOURCES += lib/compat/fnmatch.c
 libcompat_a_SOURCES += lib/compat/getopt.c
 libcompat_a_SOURCES += lib/compat/getopt_long.c
diff --git a/lib/compat/w32_wmain.c b/lib/compat/w32_wmain.c
new file mode 100644
index 0000000..4245d1c
--- /dev/null
+++ b/lib/compat/w32_wmain.c
@@ -0,0 +1,82 @@
+/* SPDX-License-Identifier: GPL-3.0-or-later */
+/*
+ * w32_wmain.c
+ *
+ * Copyright (C) 2021 David Oberhollenzer <goliath@infraroot.at>
+ */
+#include "config.h"
+#include "compat.h"
+
+#include <stdio.h>
+
+#ifdef _WIN32
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+#include <shellapi.h>
+
+#undef main
+
+int main(int argc, char **argv)
+{
+	WCHAR *cmdline, **argList;
+	int i, ret, utf8_argc;
+	char **utf8_argv;
+	(void)argc;
+	(void)argv;
+
+	/* get the UTF-16 encoded command line arguments */
+	cmdline = GetCommandLineW();
+	argList = CommandLineToArgvW(cmdline, &utf8_argc);
+	if (argList == NULL)
+		goto fail_oom;
+
+	/* convert to UTF-8 */
+	utf8_argv = calloc(sizeof(utf8_argv[0]), utf8_argc);
+	if (utf8_argv == NULL)
+		goto fail_oom;
+
+	for (i = 0; i < utf8_argc; ++i) {
+		DWORD length = WideCharToMultiByte(CP_UTF8, 0, argList[i],
+						   -1, NULL, 0, NULL, NULL);
+		if (length <= 0)
+			goto fail_conv;
+
+		utf8_argv[i] = calloc(1, length + 1);
+		if (utf8_argv[i] == NULL)
+			goto fail_oom;
+
+		WideCharToMultiByte(CP_UTF8, 0, argList[i], -1,
+				    utf8_argv[i], length + 1, NULL, NULL);
+		utf8_argv[i][length] = '\0';
+	}
+
+	LocalFree(argList);
+	argList = NULL;
+
+	/* call the actual main function */
+	ret = sqfs_tools_main(utf8_argc, utf8_argv);
+
+	/* cleanup */
+	for (i = 0; i < utf8_argc; ++i)
+		free(utf8_argv[i]);
+
+	free(utf8_argv);
+	return ret;
+fail_conv:
+	w32_perror("Converting UTF-16 argument to UTF-8");
+	goto fail;
+fail_oom:
+	fputs("out of memory\n", stderr);
+	goto fail;
+fail:
+	if (utf8_argv != NULL) {
+		for (i = 0; i < utf8_argc; ++i)
+			free(utf8_argv[i]);
+		free(utf8_argv);
+	}
+	if (argList != NULL) {
+		LocalFree(argList);
+	}
+	return EXIT_FAILURE;
+}
+#endif