//go:build !windows

package volsnap

import (
	"fmt"

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

// freeDiskBytes returns the bytes available to an unprivileged process on the
// filesystem backing path (used by the restore disk pre-check, C5). path must
// exist; callers pass the live dir's parent.
func freeDiskBytes(path string) (uint64, error) {
	var st unix.Statfs_t
	if err := unix.Statfs(path, &st); err != nil {
		return 0, fmt.Errorf("statfs %s: %w", path, err)
	}
	// Bavail is blocks available to non-root; Bsize is the fragment size.
	return st.Bavail * uint64(st.Bsize), nil
}