9p: add 9P2000.L fs.FS host support

Author: djdv

internal/filesystem/9p/server.go

@@ -0,0 +1,363 @@
+package p9
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"hash/maphash"
+	"io"
+	"io/fs"
+	"log"
+	"os"
+	"path"
+	"time"
+	"unsafe"
+
+	"github.com/djdv/go-filesystem-utils/internal/filesystem"
+	"github.com/djdv/go-filesystem-utils/internal/generic"
+	p9net "github.com/djdv/go-filesystem-utils/internal/net/9p"
+	perrors "github.com/djdv/p9/errors"
+	"github.com/djdv/p9/fsimpl/templatefs"
+	"github.com/djdv/p9/p9"
+	"github.com/multiformats/go-multiaddr"
+	manet "github.com/multiformats/go-multiaddr/net"
+)
+
+type (
+	Host struct {
+		Maddr           multiaddr.Multiaddr `json:"maddr,omitempty"`
+		ShutdownTimeout time.Duration       `json:"shutdownTimeout,omitempty"`
+	}
+	goAttacher struct {
+		fsys fs.FS
+		maphash.Hash
+	}
+	goFile struct {
+		openFlags
+		templatefs.NoopFile
+		fsys   fs.FS
+		file   fs.File
+		names  []string
+		p9.QID // TODO: the path value for this isn't spec compliant
+		// "The path is an integer unique among all files in the hierarchy. If a file is deleted and recreated with the same name in the same directory, the old and new path components of the qids should be different." intro (5)
+		// We can keep track of changes /we/ make
+		// and modify some path salt
+		// (global map[paths-hash]atomicInt |> hasher.append)
+		// but since `fs.FS` has no unique number like path, ino, etc.
+		// or even creation date, we won't know if someone else
+		// created a new file with the same path-names.
+		// tracking ops+birthtime will be best effort.
+		cursor   uint64
+		hashSeed maphash.Seed
+	}
+)
+
+const HostID filesystem.Host = "9P"
+
+func (*Host) HostID() filesystem.Host { return HostID }
+
+func (h9 *Host) UnmarshalJSON(b []byte) error {
+	// multiformats/go-multiaddr issue #100
+	var maddrWorkaround struct {
+		Maddr multiaddrContainer `json:"maddr,omitempty"`
+	}
+	if err := json.Unmarshal(b, &maddrWorkaround); err != nil {
+		return err
+	}
+	h9.Maddr = maddrWorkaround.Maddr.Multiaddr
+	return nil
+}
+
+func (h9 *Host) Mount(fsys fs.FS) (io.Closer, error) {
+	listener, err := manet.Listen(h9.Maddr)
+	if err != nil {
+		return nil, err
+	}
+	attacher := &goAttacher{
+		fsys: fsys,
+	}
+	var (
+		l = log.New(os.Stdout, "srv9 ", log.Lshortfile)
+		// TODO: opts passthrough.
+		options = []p9net.ServerOpt{
+			p9net.WithServerLogger(l),
+		}
+		server = p9net.NewServer(attacher, options...)
+		srvErr = make(chan error, 1)
+	)
+	go func() {
+		defer close(srvErr)
+		err := server.Serve(listener)
+		if err == nil ||
+			errors.Is(err, p9net.ErrServerClosed) {
+			return
+		}
+		srvErr <- err
+	}()
+	if h9.ShutdownTimeout == 0 {
+		return generic.Closer(server.Close), nil
+	}
+	var closer generic.Closer = func() error {
+		ctx, cancel := context.WithTimeout(
+			context.Background(),
+			h9.ShutdownTimeout,
+		)
+		defer cancel()
+		return errors.Join(
+			server.Shutdown(ctx),
+			<-srvErr,
+		)
+	}
+	return closer, nil
+}
+
+func (a9 *goAttacher) Attach() (p9.File, error) {
+	return &goFile{
+		fsys: a9.fsys,
+		QID: p9.QID{
+			Type: p9.TypeDir,
+			Path: a9.Hash.Sum64(),
+		},
+		hashSeed: a9.Hash.Seed(),
+	}, nil
+}
+
+func (f9 *goFile) goName(names ...string) string {
+	if len(f9.names) == 0 {
+		return filesystem.Root
+	}
+	return path.Join(append(f9.names, names...)...)
+}
+
+func (f9 *goFile) makeHasher() (hasher maphash.Hash, err error) {
+	hasher.SetSeed(f9.hashSeed)
+	err = f9.hashNames(&hasher)
+	return
+}
+
+func (f9 *goFile) hashNames(hasher *maphash.Hash) error {
+	for _, name := range f9.names {
+		if _, err := hasher.WriteString(name); err != nil {
+			return err
+		}
+	}
+	return nil
+}
+
+func (f9 *goFile) Walk(names []string) ([]p9.QID, p9.File, error) {
+	if len(names) == 0 {
+		if f9.opened() {
+			return nil, nil, fidOpenedErr
+		}
+		file := &goFile{
+			fsys:     f9.fsys,
+			hashSeed: f9.hashSeed,
+			QID:      f9.QID,
+			names:    f9.names,
+		}
+		return nil, file, nil
+	}
+	hasher, err := f9.makeHasher()
+	if err != nil {
+		return nil, nil, err
+	}
+	qids := make([]p9.QID, len(names))
+	for i, name := range names {
+		info, err := fs.Stat(f9.fsys, f9.goName(names[:i+1]...))
+		if err != nil {
+			return qids[:i], nil, err
+		}
+		if _, err := hasher.WriteString(name); err != nil {
+			return qids[:i], nil, err
+		}
+		qids[i] = p9.QID{
+			Type: goToQIDType(info.Mode().Type()),
+			Path: hasher.Sum64(),
+		}
+	}
+	file := &goFile{
+		fsys:     f9.fsys,
+		hashSeed: f9.hashSeed,
+		QID:      qids[len(qids)-1],
+		names:    append(f9.names, names...),
+	}
+	return qids, file, nil
+}
+
+func goToQIDType(typ fs.FileMode) p9.QIDType {
+	switch typ {
+	default:
+		return p9.TypeRegular
+	case fs.ModeDir:
+		return p9.TypeDir
+	case fs.ModeAppend:
+		return p9.TypeAppendOnly
+	case fs.ModeExclusive:
+		return p9.TypeExclusive
+	case fs.ModeTemporary:
+		return p9.TypeTemporary
+	case fs.ModeSymlink:
+		return p9.TypeSymlink
+	}
+}
+
+func (f9 *goFile) GetAttr(req p9.AttrMask) (p9.QID, p9.AttrMask, p9.Attr, error) {
+	var (
+		attr      p9.Attr
+		valid     p9.AttrMask
+		info, err = fs.Stat(f9.fsys, f9.goName())
+	)
+	if err != nil {
+		return f9.QID, valid, attr, err
+	}
+	attr.Mode, valid.Mode = p9.ModeFromOS(info.Mode()), true
+	attr.Size, valid.Size = uint64(info.Size()), true
+	var (
+		modTime = info.ModTime()
+		mSec    = uint64(modTime.Unix())
+		mNSec   = uint64(modTime.UnixNano())
+	)
+	attr.MTimeSeconds, attr.MTimeNanoSeconds,
+		valid.MTime = mSec, mNSec, true
+	if atimer, ok := info.(filesystem.AccessTimeInfo); ok {
+		var (
+			accessTime = atimer.AccessTime()
+			aSec       = uint64(accessTime.Unix())
+			aNSec      = uint64(accessTime.UnixNano())
+		)
+		attr.ATimeSeconds, attr.ATimeNanoSeconds,
+			valid.ATime = aSec, aNSec, true
+	}
+	if ctimer, ok := info.(filesystem.ChangeTimeInfo); ok {
+		var (
+			changeTime = ctimer.ChangeTime()
+			cSec       = uint64(changeTime.Unix())
+			cNSec      = uint64(changeTime.UnixNano())
+		)
+		attr.CTimeSeconds, attr.CTimeNanoSeconds,
+			valid.CTime = cSec, cNSec, true
+	}
+	if crtimer, ok := info.(filesystem.CreationTimeInfo); ok {
+		var (
+			birthTime = crtimer.CreationTime()
+			bSec      = uint64(birthTime.Unix())
+			bNSec     = uint64(birthTime.UnixNano())
+		)
+		attr.BTimeSeconds, attr.BTimeNanoSeconds,
+			valid.BTime = bSec, bNSec, true
+	}
+	return f9.QID, valid, attr, nil
+}
+
+func (f9 *goFile) Open(mode p9.OpenFlags) (p9.QID, ioUnit, error) {
+	if f9.opened() {
+		return f9.QID, 0, perrors.EINVAL
+	}
+	var (
+		file fs.File
+		err  error
+		name = f9.goName()
+	)
+	if mode.Mode() == p9.ReadOnly {
+		file, err = f9.fsys.Open(name)
+	} else {
+		opener, ok := f9.fsys.(filesystem.OpenFileFS)
+		if !ok {
+			return f9.QID, 0, perrors.EROFS
+		}
+		// TODO: mode conversion - 9P.L to OS independent representation
+		file, err = opener.OpenFile(name, int(mode), 0)
+	}
+	if err != nil {
+		return p9.QID{}, 0, err
+	}
+	f9.file = file
+	f9.openFlags = f9.withOpenedFlag(mode)
+	return f9.QID, noIOUnit, nil
+}
+
+func (f9 *goFile) Readdir(offset uint64, count uint32) (p9.Dirents, error) {
+	if !f9.canRead() {
+		return nil, perrors.EBADF
+	}
+	directory, ok := f9.file.(fs.ReadDirFile)
+	if !ok {
+		return nil, perrors.ENOTDIR
+	}
+	if offset != f9.cursor {
+		return nil, perrors.ENOENT
+	}
+	const entrySize = unsafe.Sizeof(p9.Dirent{})
+	countGo := int(count / uint32(entrySize)) // Bytes -> index.
+	ents, err := directory.ReadDir(countGo)
+	if err != nil {
+		if errors.Is(err, io.EOF) {
+			err = nil
+		}
+		return nil, err
+	}
+	var (
+		entryOffset = f9.cursor + 1
+		entryCount  = len(ents)
+	)
+	f9.cursor += uint64(entryCount)
+	entries := make(p9.Dirents, entryCount)
+	hasher, err := f9.makeHasher()
+	if err != nil {
+		return nil, err
+	}
+	end := entryCount - 1
+	for i, ent := range ents {
+		var (
+			name = ent.Name()
+			typ  = goToQIDType(ent.Type())
+		)
+		if _, err := hasher.WriteString(name); err != nil {
+			return nil, err
+		}
+		entries[i] = p9.Dirent{
+			Name: name,
+			QID: p9.QID{
+				Type: typ,
+				Path: hasher.Sum64(),
+			},
+			Offset: entryOffset,
+			Type:   typ,
+		}
+		if i == end {
+			break
+		}
+		entryOffset++
+		hasher.Reset()
+		if err := f9.hashNames(&hasher); err != nil {
+			return nil, err
+		}
+	}
+	return entries, nil
+}
+
+func (f9 *goFile) ReadAt(p []byte, offset int64) (int, error) {
+	if !f9.canRead() {
+		return -1, perrors.EBADF
+	}
+	var (
+		file       = f9.file
+		seeker, ok = file.(io.Seeker)
+	)
+	if !ok {
+		return -1, perrors.ESPIPE
+	}
+	if _, err := seeker.Seek(offset, io.SeekStart); err != nil {
+		return -1, err
+	}
+	return file.Read(p)
+}
+
+func (f9 *goFile) Close() error {
+	f9.openFlags = 0
+	if file := f9.file; file != nil {
+		f9.file = nil
+		return file.Close()
+	}
+	return nil
+}