virt.go

package main

import (
	"io/fs"
	"os"
	"path"
)

var (
	osFiles   = []*os.File{os.Stdin, os.Stdout, os.Stderr}
	virtFiles = make(map[string]fs.File, len(osFiles))
)

func init() {
	for _, f := range osFiles {
		virtFiles[f.Name()] = virtFile{f}
	}
}

type virtFile struct{ fs.File }

func (_ virtFile) Close() error {
	return nil
}

type virtFS struct{}

var _ fs.FS = (*virtFS)(nil)

func (_ virtFS) Open(name string) (fs.File, error) {
	f, ok := virtFiles[name]
	if !ok {
		return nil, fs.ErrNotExist
	}

	return f, nil
}

var _ fs.GlobFS = (*virtFS)(nil)

func (_ virtFS) Glob(pattern string) ([]string, error) {
	var matches []string
	for name := range virtFiles {
		matched, err := path.Match(pattern, name)
		if err != nil {
			return nil, err
		}
		if !matched {
			continue
		}

		matches = append(matches, name)
	}

	return matches, nil
}