tstor/src/vfs/utils.go

package vfs

import (
	"context"
	"path"
	"strings"
	"sync"
	"time"
)

const Separator = "/"

func IsRoot(filename string) bool {
	return path.Clean(filename) == Separator
}

func trimRelPath(p, t string) string {
	return strings.Trim(strings.TrimPrefix(p, t), "/")
}

// func clean(p string) string {
// 	return path.Clean(Separator + strings.ReplaceAll(p, "\\", "/"))
// }

func AbsPath(p string) string {
	if p == "" || p[0] != '/' {
		return Separator + p
	}
	return p
}

func AddTrailSlash(p string) string {
	if p == "" || p[len(p)-1] != '/' {
		return p + Separator
	}
	return p
}

// OnceValueWOErr returns a function that invokes f only once and returns the value
// returned by f . The returned function may be called concurrently.
//
// If f panics, the returned function will panic with the same value on every call.
func OnceValueWOErr[T any](f func() (T, error)) func() (T, error) {
	var (
		mu         sync.Mutex
		isExecuted bool
		r1         T
		err        error
	)

	return func() (T, error) {
		mu.Lock()
		defer mu.Unlock()

		if isExecuted && err == nil {
			return r1, nil
		}

		r1, err = f()
		return r1, err
	}
}

func subTimeout(ctx context.Context) (context.Context, context.CancelFunc) {
	if deadline, ok := ctx.Deadline(); ok {
		timeout := time.Until(deadline) / 2
		return context.WithTimeout(ctx, timeout)
	}

	return ctx, func() {}
}