refactor: migrate project from C++ to Rust

- establish basic Rust project layout.
- move all old code into independent directory.

legacy/wfassoc_example/main.c

@@ -0,0 +1,81 @@
+#include "../wfassoc/wfassoc.h"
+#include <stdio.h>
+#include <tchar.h>
+
+#define COMMAND_MAX_LENGTH 128
+
+WFAPP_PROFILE* create_profile();
+TCHAR* create_progId();
+void free_profile(WFAPP_PROFILE* profile);
+
+int main(int argc, char* args[]) {
+
+	// alloc application profile
+	WFAPP_PROFILE* profile = create_profile();
+	if (profile == NULL) {
+		puts("Error: Fail to allocating profile structure.\n");
+		return 1;
+	}
+	
+	// alloc input string and check it
+	char* input_str = malloc(sizeof(char) * (COMMAND_MAX_LENGTH + 1));
+	if (input_str == NULL) return;
+	
+	// accept input
+	while (TRUE) {
+		gets_s(input_str, COMMAND_MAX_LENGTH);
+		if (!strcmp(input_str, "install")) {
+			_tprintf(TEXT("%s\n"), profile->ProgID);
+		} else if (!strcmp(input_str, "uninstall")) {
+			_tprintf(TEXT("%s\n"), profile->ProgID);
+		} else if (!strcmp(input_str, "quit")) {
+			break;
+		}
+	}
+
+	//free input string
+	free(input_str);
+	return 0;
+}
+
+WFAPP_PROFILE* create_profile() {
+	WFAPP_PROFILE* profile = (WFAPP_PROFILE*)malloc(sizeof(WFAPP_PROFILE));
+	if (profile == NULL) return NULL;
+	memset(profile, 0, sizeof(WFAPP_PROFILE));
+
+	profile->WFVersion = WFVERSION;
+	profile->AppPath = TEXT("E:\\pineapple-picture\\ppic.exe");
+	profile->AppCommand = TEXT("E:\\pineapple-picture\\ppic.exe \"%1\"");
+	profile->SupportedTypes = TEXT(".png\0.jpg\0");
+	profile->ProgID = create_progId();
+	if (profile->ProgID == NULL) {
+		free_profile(profile);
+		return NULL;
+	}
+
+	return profile;
+}
+
+TCHAR* create_progId() {
+	TCHAR* progid = NULL;
+	int progIdSize;
+	if (WFFAILED(WFGenerateProgID(TEXT("PineapplePicture"), TEXT("Image"), 0, NULL, &progIdSize))) {
+		return NULL;
+	}
+
+	progid = (TCHAR*)malloc(sizeof(TCHAR) * progIdSize);
+	if (progid == NULL) return NULL;
+	memset(progid, 0, sizeof(TCHAR) * progIdSize);
+
+	if (WFFAILED(WFGenerateProgID(TEXT("PineapplePicture"), TEXT("Image"), 0, progid, &progIdSize))) {
+		free(progid);
+		return NULL;
+	}
+
+	return progid;
+}
+
+void free_profile(WFAPP_PROFILE* profile) {
+	if (profile->ProgID != NULL) free(profile->ProgID);
+	free(profile);
+}