isle/go/daemon/jigs.go

package daemon

import (
	"crypto/rand"
	"encoding/hex"
	"errors"
	"fmt"
	"io/fs"
	"os"
	"path/filepath"
)

func randStr(l int) string {
	b := make([]byte, l)
	if _, err := rand.Read(b); err != nil {
		panic(err)
	}
	return hex.EncodeToString(b)
}

// mkDir is like os.Mkdir but it returns better error messages. If the directory
// already exists then nil is returned.
func mkDir(path string) error {
	{
		parentPath := filepath.Dir(path)
		parentInfo, err := os.Stat(parentPath)
		if err != nil {
			return fmt.Errorf("checking fs node of parent %q: %w", parentPath, err)
		} else if !parentInfo.IsDir() {
			return fmt.Errorf("%q is not a directory", parentPath)
		}
	}

	info, err := os.Stat(path)
	if errors.Is(err, fs.ErrNotExist) {
		// fine
	} else if err != nil {
		return fmt.Errorf("checking fs node: %w", err)
	} else if !info.IsDir() {
		return fmt.Errorf("exists but is not a directory")
	} else {
		return nil
	}

	if err := os.Mkdir(path, 0700); err != nil {
		return fmt.Errorf("creating directory: %w", err)
	}

	return nil
}