Add cgo support for DesyncUntar function

godot_cgo.md

@@ -0,0 +1,70 @@
+# Godot cgo enhancement proposal
+
+The `cgo` feature in Go programming allows you to call C code from Go and vice versa. This can be used to provide a C interface for the `desync` Go library.
+
+## Updating the C Interface
+
+To expose the output directory and the cache directory, you can modify the `DesyncUntar` function to accept these as parameters. Here's how you could do it:
+
+```go
+package main
+
+/*
+#include <stdlib.h>
+*/
+import "C"
+import (
+    "os/exec"
+    "unsafe"
+    "errors"
+    "context"
+)
+
+// DesyncUntar is a C-exported function
+func DesyncUntar(storeUrl *C.char, indexUrl *C.char, outputDir *C.char, cacheDir *C.char) error {
+    store := C.GoString(storeUrl)
+    index := C.GoString(indexUrl)
+    output := C.GoString(outputDir)
+    cache := C.GoString(cacheDir)
+
+    if store == "" || index == "" || output == "" {
+        return errors.New("storeUrl, indexUrl, and outputDir are required")
+    }
+
+    args := []string{"--no-same-owner", "--store", store, "--index", index, output}
+    if cache != "" {
+        args = append(args, "--cache", cache)
+    }
+
+    cmd := exec.CommandContext(context.Background(), "desync", args...)
+    err := cmd.Run()
+    if err != nil {
+        return err
+    }
+    return nil
+}
+
+func main() {}
+```
+
+## Using the Updated Static Library in C Program
+
+You can then call this function from your C program like this:
+
+```c
+#include <stdio.h>
+#include "desync_c_interface.h"
+
+int main() {
+    int result = DesyncUntar("https://v-sekai.github.io/casync-v-sekai-game/store", 
+                "https://github.com/V-Sekai/casync-v-sekai-game/raw/main/vsekai_game_windows_x86_64.caidx",
+                "/path/to/output/directory",
+                "/path/to/cache/directory");
+    if (result != 0) {
+        printf("Error: storeUrl, indexUrl, and outputDir are required\n");
+    }
+    return 0;
+}
+```
+
+In this C code, the `DesyncUntar` function is called with four parameters: the store URL, the index URL, the output directory, and the cache directory.