sandbox/vfs: expose mountinfo line scanning
Signed-off-by: Ophestra <cat@gensokyo.uk>
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241702ae3a
commit
66908ddc05
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SHA256:gQ67O0enBZ7UdZypgtspB2FDM1g3GVw8nX0XSdcFw8Q
@ -5,6 +5,7 @@ import (
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"errors"
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"fmt"
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"io"
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"iter"
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"strconv"
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"strings"
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"syscall"
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@ -18,13 +19,23 @@ var (
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)
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type (
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// MountInfo represents a /proc/pid/mountinfo document.
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// A MountInfoDecoder reads and decodes proc_pid_mountinfo(5) entries from an input stream.
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MountInfoDecoder struct {
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s *bufio.Scanner
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m *MountInfo
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current *MountInfo
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parseErr error
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complete bool
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}
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// MountInfo represents the contents of a proc_pid_mountinfo(5) document.
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MountInfo struct {
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Next *MountInfo
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MountInfoEntry
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}
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// MountInfoEntry represents a line in /proc/pid/mountinfo.
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// MountInfoEntry represents a proc_pid_mountinfo(5) entry.
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MountInfoEntry struct {
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// mount ID: a unique ID for the mount (may be reused after umount(2)).
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ID int `json:"id"`
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@ -77,95 +88,145 @@ func (e *MountInfoEntry) Flags() (flags uintptr, unmatched []string) {
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return
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}
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// ParseMountInfo parses a mountinfo file according to proc_pid_mountinfo(5).
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func ParseMountInfo(r io.Reader) (*MountInfo, int, error) {
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var m, cur *MountInfo
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s := bufio.NewScanner(r)
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var n int
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for s.Scan() {
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n++
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if cur == nil {
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m = new(MountInfo)
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cur = m
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} else {
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cur.Next = new(MountInfo)
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cur = cur.Next
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}
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// prevent proceeding with misaligned fields due to optional fields
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f := strings.Split(s.Text(), " ")
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if len(f) < 10 {
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return nil, -1, ErrMountInfoFields
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}
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// 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
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// (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
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// (1) id
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if id, err := strconv.Atoi(f[0]); err != nil { // 0
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return nil, -1, err
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} else {
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cur.ID = id
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}
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// (2) parent
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if parent, err := strconv.Atoi(f[1]); err != nil { // 1
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return nil, -1, err
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} else {
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cur.Parent = parent
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}
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// (3) maj:min
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if n, err := fmt.Sscanf(f[2], "%d:%d", &cur.Devno[0], &cur.Devno[1]); err != nil {
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return nil, -1, err
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} else if n != 2 {
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// unreachable
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return nil, -1, ErrMountInfoDevno
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}
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// (4) mountroot
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cur.Root = Unmangle(f[3])
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if cur.Root == "" {
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return nil, -1, ErrMountInfoEmpty
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}
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// (5) target
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cur.Target = Unmangle(f[4])
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if cur.Target == "" {
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return nil, -1, ErrMountInfoEmpty
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}
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// (6) vfs options (fs-independent)
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cur.VfsOptstr = Unmangle(f[5])
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if cur.VfsOptstr == "" {
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return nil, -1, ErrMountInfoEmpty
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}
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// (7) optional fields, terminated by " - "
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i := len(f) - 4
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cur.OptFields = f[6:i]
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// (8) optional fields end marker
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if f[i] != "-" {
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return nil, -1, ErrMountInfoSep
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}
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i++
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// (9) FS type
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cur.FsType = Unmangle(f[i])
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if cur.FsType == "" {
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return nil, -1, ErrMountInfoEmpty
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}
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i++
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// (10) source -- maybe empty string
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cur.Source = Unmangle(f[i])
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i++
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// (11) fs options (fs specific)
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cur.FsOptstr = Unmangle(f[i])
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}
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return m, n, s.Err()
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// NewMountInfoDecoder returns a new decoder that reads from r.
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//
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// The decoder introduces its own buffering and may read data from r beyond the mountinfo entries requested.
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func NewMountInfoDecoder(r io.Reader) *MountInfoDecoder {
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return &MountInfoDecoder{s: bufio.NewScanner(r)}
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}
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func (d *MountInfoDecoder) Decode(v **MountInfo) (err error) {
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for d.scan() {
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}
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err = d.Err()
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if err == nil {
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*v = d.m
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}
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return
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}
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// Entries returns an iterator over mountinfo entries.
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func (d *MountInfoDecoder) Entries() iter.Seq[*MountInfoEntry] {
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return func(yield func(*MountInfoEntry) bool) {
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for cur := d.m; cur != nil; cur = cur.Next {
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if !yield(&cur.MountInfoEntry) {
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return
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}
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}
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for d.scan() {
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if !yield(&d.current.MountInfoEntry) {
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return
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}
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}
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}
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}
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func (d *MountInfoDecoder) Err() error {
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if err := d.s.Err(); err != nil {
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return err
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}
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return d.parseErr
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}
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func (d *MountInfoDecoder) scan() bool {
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if d.complete {
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return false
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}
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if !d.s.Scan() {
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d.complete = true
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return false
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}
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m := new(MountInfo)
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if err := parseMountInfoLine(d.s.Text(), &m.MountInfoEntry); err != nil {
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d.parseErr = err
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d.complete = true
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return false
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}
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if d.current == nil {
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d.m = m
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d.current = d.m
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} else {
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d.current.Next = m
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d.current = d.current.Next
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}
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return true
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}
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func parseMountInfoLine(s string, ent *MountInfoEntry) error {
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// prevent proceeding with misaligned fields due to optional fields
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f := strings.Split(s, " ")
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if len(f) < 10 {
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return ErrMountInfoFields
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}
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// 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
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// (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
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// (1) id
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if id, err := strconv.Atoi(f[0]); err != nil { // 0
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return err
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} else {
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ent.ID = id
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}
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// (2) parent
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if parent, err := strconv.Atoi(f[1]); err != nil { // 1
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return err
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} else {
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ent.Parent = parent
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}
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// (3) maj:min
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if n, err := fmt.Sscanf(f[2], "%d:%d", &ent.Devno[0], &ent.Devno[1]); err != nil {
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return err
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} else if n != 2 {
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// unreachable
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return ErrMountInfoDevno
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}
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// (4) mountroot
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ent.Root = Unmangle(f[3])
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if ent.Root == "" {
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return ErrMountInfoEmpty
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}
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// (5) target
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ent.Target = Unmangle(f[4])
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if ent.Target == "" {
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return ErrMountInfoEmpty
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}
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// (6) vfs options (fs-independent)
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ent.VfsOptstr = Unmangle(f[5])
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if ent.VfsOptstr == "" {
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return ErrMountInfoEmpty
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}
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// (7) optional fields, terminated by " - "
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i := len(f) - 4
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ent.OptFields = f[6:i]
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// (8) optional fields end marker
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if f[i] != "-" {
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return ErrMountInfoSep
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}
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i++
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// (9) FS type
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ent.FsType = Unmangle(f[i])
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if ent.FsType == "" {
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return ErrMountInfoEmpty
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}
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i++
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// (10) source -- maybe empty string
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ent.Source = Unmangle(f[i])
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i++
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// (11) fs options (fs specific)
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ent.FsOptstr = Unmangle(f[i])
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return nil
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}
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@ -2,6 +2,7 @@ package vfs_test
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import (
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"errors"
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"iter"
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"reflect"
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"slices"
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"strconv"
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@ -122,57 +123,106 @@ id 20 0:53 / /mnt/test rw,relatime shared:212 - tmpfs rw
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for _, tc := range testCases {
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t.Run(tc.name, func(t *testing.T) {
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got, n, err := vfs.ParseMountInfo(strings.NewReader(tc.sample))
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if !errors.Is(err, tc.wantErr) {
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if tc.wantError == "" {
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t.Errorf("ParseMountInfo: error = %v, wantErr %v",
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err, tc.wantErr)
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} else if err != nil && err.Error() != tc.wantError {
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t.Errorf("ParseMountInfo: error = %q, wantError %q",
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err, tc.wantError)
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}
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}
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t.Run("decode", func(t *testing.T) {
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var got *vfs.MountInfo
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d := vfs.NewMountInfoDecoder(strings.NewReader(tc.sample))
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err := d.Decode(&got)
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checkMountInfo(t, true,
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tc.want, tc.wantErr, tc.wantError,
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func(yield func(*vfs.MountInfoEntry) bool) {
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for cur := got; cur != nil; cur = cur.Next {
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if !yield(&cur.MountInfoEntry) {
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return
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}
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}
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}, func() error { return err })
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t.Run("reuse", func(t *testing.T) {
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checkMountInfo(t, false,
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tc.want, tc.wantErr, tc.wantError,
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d.Entries(), d.Err)
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})
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})
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wantCount := len(tc.want)
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if tc.wantErr != nil || tc.wantError != "" {
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wantCount = -1
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}
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if n != wantCount {
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t.Errorf("ParseMountInfo: got %d entries, want %d", n, wantCount)
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}
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t.Run("iter", func(t *testing.T) {
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d := vfs.NewMountInfoDecoder(strings.NewReader(tc.sample))
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checkMountInfo(t, false,
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tc.want, tc.wantErr, tc.wantError,
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d.Entries(), d.Err)
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i := 0
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for cur := got; cur != nil; cur = cur.Next {
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if i == len(tc.want) {
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t.Errorf("ParseMountInfo: got more than %d entries", len(tc.want))
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break
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}
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t.Run("reuse", func(t *testing.T) {
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checkMountInfo(t, false,
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tc.want, tc.wantErr, tc.wantError,
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d.Entries(), d.Err)
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})
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})
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if !reflect.DeepEqual(&cur.MountInfoEntry, &tc.want[i].MountInfoEntry) {
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t.Errorf("ParseMountInfo: entry %d\ngot: %#v\nwant: %#v",
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i, cur.MountInfoEntry, tc.want[i])
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}
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t.Run("yield", func(t *testing.T) {
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d := vfs.NewMountInfoDecoder(strings.NewReader(tc.sample))
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v := false
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d.Entries()(func(entry *vfs.MountInfoEntry) bool { v = !v; return v })
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d.Entries()(func(entry *vfs.MountInfoEntry) bool { return false })
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flags, unmatched := cur.Flags()
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if flags != tc.want[i].flags {
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t.Errorf("Flags(%q): %#x, want %#x",
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cur.VfsOptstr, flags, tc.want[i].flags)
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}
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if !slices.Equal(unmatched, tc.want[i].unmatched) {
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t.Errorf("Flags(%q): unmatched = %#q, want %#q",
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cur.VfsOptstr, unmatched, tc.want[i].unmatched)
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}
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checkMountInfo(t, false,
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tc.want, tc.wantErr, tc.wantError,
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d.Entries(), d.Err)
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i++
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}
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if i != len(tc.want) {
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t.Errorf("ParseMountInfo: got %d entries, want %d", i, len(tc.want))
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}
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t.Run("reuse", func(t *testing.T) {
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checkMountInfo(t, false,
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tc.want, tc.wantErr, tc.wantError,
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d.Entries(), d.Err)
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})
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})
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})
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}
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}
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func checkMountInfo(t *testing.T, checkDecode bool,
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want []*wantMountInfo, wantErr error, wantError string,
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got iter.Seq[*vfs.MountInfoEntry], gotErr func() error) {
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i := 0
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for cur := range got {
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if i == len(want) {
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if !checkDecode && (wantErr != nil || wantError != "") {
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continue
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}
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t.Errorf("ParseMountInfo: got more than %d entries", len(want))
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break
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}
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if !reflect.DeepEqual(cur, &want[i].MountInfoEntry) {
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t.Errorf("ParseMountInfo: entry %d\ngot: %#v\nwant: %#v",
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i, cur, want[i])
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}
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flags, unmatched := cur.Flags()
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if flags != want[i].flags {
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t.Errorf("Flags(%q): %#x, want %#x",
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cur.VfsOptstr, flags, want[i].flags)
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}
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if !slices.Equal(unmatched, want[i].unmatched) {
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t.Errorf("Flags(%q): unmatched = %#q, want %#q",
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cur.VfsOptstr, unmatched, want[i].unmatched)
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}
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i++
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}
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if i != len(want) {
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t.Errorf("ParseMountInfo: got %d entries, want %d", i, len(want))
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}
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if err := gotErr(); !errors.Is(err, wantErr) {
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if wantError == "" {
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t.Errorf("ParseMountInfo: error = %v, wantErr %v",
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err, wantErr)
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} else if err != nil && err.Error() != wantError {
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t.Errorf("ParseMountInfo: error = %q, wantError %q",
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err, wantError)
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}
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}
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}
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type wantMountInfo struct {
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vfs.MountInfoEntry
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flags uintptr
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