//go:build linux

package assetcache

import "golang.org/x/sys/unix"

type statfsFS struct{}

// Statfs is the real FS: the kernel's answer for the filesystem holding dir.
// free counts the blocks an unprivileged writer may use (Bavail).
var Statfs FS = statfsFS{}

func (statfsFS) Space(dir string) (total, free uint64, err error) {
	var st unix.Statfs_t
	if err := unix.Statfs(dir, &st); err != nil {
		return 0, 0, err
	}
	bsize := uint64(st.Bsize)
	return st.Blocks * bsize, st.Bavail * bsize, nil
}