Passing variable reference to WalkDirFunc-CodePudding

I am working to recursively iterate through a given directory and store the name of files found and their sizes in a map[string]uint32. I've found a post describing how to recursively walk a specified directory using the path/filepath/WalkDir function and a WalkDirFunc.

I am relatively new to Go, and haven't been able to find a way to pass a reference to my map to the WalkDirFunc since its signature specifies three parameters only:

func main() {
    args := os.Args
    if len(args) != 2 {
        msg := fmt.Sprintf("Usage: %v <path_to_directory>", args[0])
        log.Fatal(msg)
    }

    fullPath := args[1]
    dirMap := make(map[string]uint32)

    filepath.WalkDir(fullPath, walk)

}

// how to create parameter accepting &map[string]uint32
func walk(path string, entry fs.DirEntry, err error) error {
    if err != nil {
        return err
    }

    if !entry.IsDir() {
        // add entry and it's size to dirMap

        file, err := os.Stat(path)
        if err != nil {
            log.Println("Error determining file size:", err)
        }

        size := file.Size()

        // add path and size to dirMap

    } else if entry.IsDir() {
        // recurse here

    } else {
        log.Println("Unhandled branch:")
        log.Println(entry.Info())
    }

    return nil
}

EDIT: Since walk is a WalkDirFunc passed to filepath.walkDir, it is necessary to pass the map beginning here. In Python, I would use named parameters to accomplish this, but what is the best way in Go?

func main() {
    args := os.Args
    ...

    fullPath := args[1]
    dirMap := make(map[string]uint32)


    // dirMap should be passed here
    filepath.WalkDir(fullPath, walk)

}

CodePudding user response：

Use a closure. Change walk to:

func walk(dirMap map[string]uint32, path string, entry fs.DirEntry, err error) error {
    ...
}

Call WalkDir like this:

dirMap := make(map[string]uint32)
filepath.WalkDir(fullPath, func(path string, entry fs.DirEntry, err error) error {
    return walk(dirMap, path, entry, err)
})

Run the example here: https://go.dev/play/p/rjV2rSBsUDz