.

wcfs/misc.go

@@ -23,6 +23,8 @@ package main
 import (
 	"context"
 	"fmt"
+	"io"
+	"math"
 	"syscall"
 
 	log "github.com/golang/glog"
@@ -37,6 +39,7 @@ import (
 	"lab.nexedi.com/kirr/neo/go/zodb"
 )
 
+// ---- FUSE ----
 
 // eInvalError is the error wrapper signifying that underlying error is about "invalid argument".
 // err2LogStatus converts such errors into EINVAL return code + logs as warning.
@@ -138,7 +141,7 @@ func (f *SmallFile) Read(_ nodefs.File, dest []byte, off int64, _ *fuse.Context)
 // mkdir adds child to parent as directory.
 //
 // Note: parent must be already in the filesystem tree - i.e. associated
-// with inode. if not - nodefs will panic in Inode.NewChild on nil dereference.
+// with Inode. if not - nodefs will panic in Inode.NewChild on nil dereference.
 func mkdir(parent nodefs.Node, name string, child nodefs.Node) {
 	parent.Inode().NewChild(name, true, child)
 }
@@ -166,6 +169,155 @@ func mount(mntpt string, root nodefs.Node, opts *fuse.MountOptions) (*fuse.Serve
 	return fssrv, fsconn, nil
 }
 
+
+// FileSock is bidirectional channel associated with opened file.
+//
+// FileSock provides streaming write/read operations for filesystem server that
+// are correspondingly matched with read/write operations on filesystem user side.
+type FileSock struct {
+	file *skFile        // filesock's file peer
+	rx   *io.PipeReader // socket reads from file here
+	tx   *io.PipeWriter // socket writes to file here
+}
+
+// skFile is File peer of FileSock.
+//
+// skFile.Read  is connected with sk.Write.
+// skFile.Write is connected with sk.Read.
+//
+// skFile is always created with nonseekable & directio flags, to support
+// streaming semantics.
+type skFile struct {
+	nodefs.File
+
+	rx *io.PipeReader // file reads from socket here
+	tx *io.PipeWriter // file writes to socket here
+}
+
+// NewFileSock creates new file socket.
+//
+// After file socket is created, File return should be given to kernel for the
+// socket to be connected to an opened file.
+func NewFileSock() *FileSock {
+	sk := &FileSock{}
+	f  := &skFile{
+		File: nodefs.NewDefaultFile(),
+	}
+	sk.file = f
+
+	rx, tx := io.Pipe()
+	sk.rx = rx
+	f .tx = tx
+
+	rx, tx = io.Pipe()
+	sk.rx = rx
+	f .tx = tx
+
+	return sk
+}
+
+// File returns nodefs.File handle that is connected to the socket.
+//
+// The handle should be given to kernel as result of a file open, for that file
+// to be connected to the socket.
+func (sk *FileSock) File() nodefs.File {
+	// nonseekable & directio for opened file to have streaming semantic as
+	// if it was a socket.
+	return &nodefs.WithFlags{
+		File:      sk.file,
+		FuseFlags: fuse.FOPEN_NONSEEKABLE | fuse.FOPEN_DIRECT_IO,
+	}
+}
+
+
+// Write writes data to filesock.
+//
+// The data will be read by client reading from filesock's file.
+// Write semantic is that of io.Writer.
+func (sk *FileSock) Write(data []byte) (n int, err error) {
+	return sk.tx.Write(data)
+}
+
+// Read implements nodefs.File and is paired with filesock.Write().
+func (f *skFile) Read(dest []byte, /*ignored*/off int64) (fuse.ReadResult, fuse.Status) {
+	n, err := f.rx.Read(dest)
+	if n != 0 {
+		err = nil
+	}
+	if err == io.EOF {
+		// XXX what here?
+	}
+	if err != nil {
+		return nil, err2LogStatus(err)
+	}
+	return fuse.ReadResultData(dest), fuse.OK
+}
+
+
+// Read reads data from filesock.
+//
+// The data read will be that the client writes into filesock's file.
+// Read semantic is that of io.Reader.
+func (sk *FileSock) Read(dest []byte) (n int, err error) {
+	return sk.rx.Read(dest)
+}
+
+// Write implements nodefs.File and is paired with filesock.Read()
+func (f *skFile) Write(data []byte, /*ignored*/off int64) (uint32, fuse.Status) {
+	// cap data to 2GB (not 4GB not to overflow int on 32-bit platforms)
+	l := len(data)
+	if l > math.MaxInt32 {
+		l = math.MaxInt32
+		data = data[:l]
+	}
+
+	n, err := f.tx.Write(data)
+	if n != 0 {
+		err = nil
+	}
+	if err == io.ErrClosedPipe {
+		// XXX what here?
+	}
+	if err != nil {
+		return 0, err2LogStatus(err)
+	}
+	return uint32(n), fuse.OK
+}
+
+
+// CloseRead closes reading side of the socket.
+func (sk *FileSock) CloseRead() error {
+	return sk.rx.Close()
+}
+
+// CloseWrite closes writing side of the socket.
+func (sk *FileSock) CloseWrite() error {
+	return sk.tx.Close()
+}
+
+// Close closes the socket.
+//
+// it is semantically equivalent to CloseRead + CloseWrite.
+func (sk *FileSock) Close() error {
+	err := sk.CloseRead()
+	err2 := sk.CloseWrite()
+	if err == nil {
+		err = err2
+	}
+	return err
+}
+
+// Flush implements nodefs.File to handle close(file) call.
+func (f *skFile) Flush() fuse.Status {
+	err := f.rx.Close()
+	err2 := f.tx.Close()
+	if err == nil {
+		err = err2
+	}
+	return err2LogStatus(err)
+}
+
+
 // ---- ZODB ---
 
 // typeOf returns ZODB type of an object.