Add GetDevInfo exposing BTRFS_IOC_DEV_INFO (#3)

* Add GetDevInfo exposing BTRFS_IOC_DEV_INFO

Co-authored-by: Marcus Cobden <leth@users.noreply.github.com>

btrfs.go

@@ -2,12 +2,13 @@ package btrfs
 
 import (
 	"fmt"
-	"github.com/dennwc/ioctl"
 	"io"
 	"os"
 	"path/filepath"
 	"strconv"
 	"syscall"
+
+	"github.com/dennwc/ioctl"
 )
 
 const SuperMagic = 0x9123683E
@@ -84,6 +85,28 @@ func (f *FS) Info() (out Info, err error) {
 	return
 }
 
+type DevInfo struct {
+	UUID       UUID
+	BytesUsed  uint64
+	TotalBytes uint64
+	Path       string
+}
+
+func (f *FS) GetDevInfo(id uint64) (out DevInfo, err error) {
+	var arg btrfs_ioctl_dev_info_args
+	arg.devid = id
+
+	if err = ioctl.Do(f.f, _BTRFS_IOC_DEV_INFO, &arg); err != nil {
+		return
+	}
+	out.UUID = arg.uuid
+	out.BytesUsed = arg.bytes_used
+	out.TotalBytes = arg.total_bytes
+	out.Path = stringFromBytes(arg.path[:])
+
+	return
+}
+
 type DevStats struct {
 	WriteErrs uint64
 	ReadErrs  uint64

utils.go

@@ -1,13 +1,15 @@
 package btrfs
 
 import (
+	"bytes"
 	"fmt"
-	"github.com/dennwc/btrfs/mtab"
 	"os"
 	"path/filepath"
 	"strings"
 	"syscall"
 	"unsafe"
+
+	"github.com/dennwc/btrfs/mtab"
 )
 
 func isBtrfs(path string) (bool, error) {
@@ -95,3 +97,10 @@ func treeSearchRaw(mnt *os.File, key btrfs_ioctl_search_key) (out []searchResult
 	}
 	return out, nil
 }
+
+func stringFromBytes(input []byte) string {
+	if i := bytes.IndexByte(input, 0); i >= 0 {
+		input = input[:i]
+	}
+	return string(input)
+}