//go:build linux

package main

import (
	"os"
	"unsafe"

	"syscall"
)

// BLKGETSIZE64 = _IOR(0x12, 114, sizeof(uint64)) on Linux.
const blkGetSize64 = 0x80081272

func blockDeviceSize(path string) (int64, error) {
	f, err := os.Open(path)
	if err != nil {
		return 0, err
	}
	defer f.Close()

	var size uint64
	_, _, errno := syscall.Syscall(syscall.SYS_IOCTL, f.Fd(), blkGetSize64, uintptr(unsafe.Pointer(&size)))
	if errno != 0 {
		return 0, errno
	}
	return int64(size), nil
}