Source: readdir.go in package io/fs


package fs

import (
	"errors"
	"sort"
)

ReadDirFS is the interface implemented by a file system that provides an optimized implementation of ReadDir.

type ReadDirFS interface {
	FS

ReadDir reads the named directory and returns a list of directory entries sorted by filename.

	ReadDir(name string) ([]DirEntry, error)
}

ReadDir reads the named directory and returns a list of directory entries sorted by filename. If fs implements ReadDirFS, ReadDir calls fs.ReadDir. Otherwise ReadDir calls fs.Open and uses ReadDir and Close on the returned file.

func ReadDir(fsys FS, name string) ([]DirEntry, error) {
	if fsys, ok := fsys.(ReadDirFS); ok {
		return fsys.ReadDir(name)
	}

	file, err := fsys.Open(name)
	if err != nil {
		return nil, err
	}
	defer file.Close()

	dir, ok := file.(ReadDirFile)
	if !ok {
		return nil, &PathError{Op: "readdir", Path: name, Err: errors.New("not implemented")}
	}

	list, err := dir.ReadDir(-1)
	sort.Slice(list, func(i, j int) bool { return list[i].Name() < list[j].Name() })
	return list, err