fix/32/pr-ports : Pulled changes from PR 4517

Pulled changes from ipfs/kubo#4517, on top of, ipfs#45.
Change added to unblock the `waitPub()` call. With the elimination of
stateSync cause a `updateChildEntry` to happen for `stateFlushed` as
well, causing it to propogate upwards to the parent(s) [fullSync] and
force a publish to happen, hence unblocking `waitPub`.

Author: nmalhotra

fd.go

@@ -7,6 +7,16 @@ import (
 	mod "github.com/ipfs/go-unixfs/mod"
 
 	context "context"
+
+	ipld "github.com/ipfs/go-ipld-format"
+)
+
+type state uint8
+
+const (
+	stateFlushed state = iota
+	stateDirty
+	stateClosed
 )
 
 // One `File` can have many `FileDescriptor`s associated to it
@@ -31,14 +41,31 @@ type FileDescriptor interface {
 }
 
 type fileDescriptor struct {
-	inode      *File
-	mod        *mod.DagModifier
-	perms      int
-	sync       bool
-	hasChanges bool
-
-	// TODO: Where is this variable set?
-	closed bool
+	inode *File
+	mod   *mod.DagModifier
+	flags Flags
+
+	state state
+}
+
+func (fi *fileDescriptor) checkWrite() error {
+	if fi.state == stateClosed {
+		return ErrClosed
+	}
+	if !fi.flags.Write {
+		return fmt.Errorf("file is read-only")
+	}
+	return nil
+}
+
+func (fi *fileDescriptor) checkRead() error {
+	if fi.state == stateClosed {
+		return ErrClosed
+	}
+	if !fi.flags.Read {
+		return fmt.Errorf("file is write-only")
+	}
+	return nil
 }
 
 // Size returns the size of the file referred to by this descriptor
@@ -48,69 +75,52 @@ func (fi *fileDescriptor) Size() (int64, error) {
 
 // Truncate truncates the file to size
 func (fi *fileDescriptor) Truncate(size int64) error {
-	if fi.perms == OpenReadOnly {
-		return fmt.Errorf("cannot call truncate on readonly file descriptor")
+	if err := fi.checkWrite(); err != nil {
+		return fmt.Errorf("truncate failed: %s", err)
 	}
-	fi.hasChanges = true
+	fi.state = stateDirty
 	return fi.mod.Truncate(size)
 }
 
 // Write writes the given data to the file at its current offset
 func (fi *fileDescriptor) Write(b []byte) (int, error) {
-	if fi.perms == OpenReadOnly {
-		return 0, fmt.Errorf("cannot write on not writeable descriptor")
+	if err := fi.checkWrite(); err != nil {
+		return 0, fmt.Errorf("write failed: %s", err)
 	}
-	fi.hasChanges = true
+	fi.state = stateDirty
 	return fi.mod.Write(b)
 }
 
 // Read reads into the given buffer from the current offset
 func (fi *fileDescriptor) Read(b []byte) (int, error) {
-	if fi.perms == OpenWriteOnly {
-		return 0, fmt.Errorf("cannot read on write-only descriptor")
+	if err := fi.checkRead(); err != nil {
+		return 0, fmt.Errorf("read failed: %s", err)
 	}
 	return fi.mod.Read(b)
 }
 
 // Read reads into the given buffer from the current offset
 func (fi *fileDescriptor) CtxReadFull(ctx context.Context, b []byte) (int, error) {
-	if fi.perms == OpenWriteOnly {
-		return 0, fmt.Errorf("cannot read on write-only descriptor")
+	if err := fi.checkRead(); err != nil {
+		return 0, fmt.Errorf("read failed: %s", err)
 	}
 	return fi.mod.CtxReadFull(ctx, b)
 }
 
 // Close flushes, then propogates the modified dag node up the directory structure
 // and signals a republish to occur
 func (fi *fileDescriptor) Close() error {
-	defer func() {
-		switch fi.perms {
-		case OpenReadOnly:
-			fi.inode.desclock.RUnlock()
-		case OpenWriteOnly, OpenReadWrite:
-			fi.inode.desclock.Unlock()
-		}
-		// TODO: `closed` should be set here.
-	}()
-
-	if fi.closed {
-		panic("attempted to close file descriptor twice!")
+	if fi.state == stateClosed {
+		return ErrClosed
 	}
-
-	if fi.hasChanges {
-		err := fi.mod.Sync()
-		if err != nil {
-			return err
-		}
-
-		fi.hasChanges = false
-
-		// explicitly stay locked for flushUp call,
-		// it will manage the lock for us
-		return fi.flushUp(fi.sync)
+	if fi.flags.Write {
+		defer fi.inode.desclock.Unlock()
+	} else if fi.flags.Read {
+		defer fi.inode.desclock.RUnlock()
 	}
-
-	return nil
+	err := fi.flushUp(fi.flags.Sync)
+	fi.state = stateClosed
+	return err
 }
 
 // Flush generates a new version of the node of the underlying
@@ -126,47 +136,57 @@ func (fi *fileDescriptor) Flush() error {
 // If `fullSync` is set the changes are propagated upwards
 // (the `Up` part of `flushUp`).
 func (fi *fileDescriptor) flushUp(fullSync bool) error {
-	nd, err := fi.mod.GetNode()
-	if err != nil {
-		return err
-	}
+	var nd ipld.Node
+	switch fi.state {
+	case stateDirty:
+		// calls mod.Sync internally.
+		var err error
+		nd, err = fi.mod.GetNode()
+		if err != nil {
+			return err
+		}
+		err = fi.inode.dagService.Add(context.TODO(), nd)
+		if err != nil {
+			return err
+		}
+		fi.inode.nodeLock.Lock()
+		fi.inode.node = nd
+		fi.inode.nodeLock.Unlock()
+		fallthrough
+	case stateFlushed:
+		if !fullSync {
+			return nil
+		}
 
-	err = fi.inode.dagService.Add(context.TODO(), nd)
-	if err != nil {
-		return err
-	}
-	// TODO: Very similar logic to the update process in
-	// `Directory`, the logic should be unified, both structures
-	// (`File` and `Directory`) are backed by a IPLD node with
-	// a UnixFS format that is the actual target of the update
-	// (regenerating it and adding it to the DAG service).
-
-	fi.inode.nodeLock.Lock()
-	fi.inode.node = nd
-	// TODO: Create a `SetNode` method.
-	name := fi.inode.name
-	parent := fi.inode.parent
-	// TODO: Can the parent be modified? Do we need to do this inside the lock?
-	fi.inode.nodeLock.Unlock()
-	// TODO: Maybe all this logic should happen in `File`.
-
-	if fullSync {
-		return parent.updateChildEntry(child{name, nd})
-	}
+		fi.inode.nodeLock.Lock()
+		nd = fi.inode.node
+		parent := fi.inode.parent
+		name := fi.inode.name
+		fi.inode.nodeLock.Unlock()
 
-	return nil
+		if err := parent.updateChildEntry(child{name, nd}); err != nil {
+			return err
+		}
+		fi.state = stateFlushed
+		return nil
+	default:
+		panic("invalid state")
+	}
 }
 
 // Seek implements io.Seeker
 func (fi *fileDescriptor) Seek(offset int64, whence int) (int64, error) {
+	if fi.state == stateClosed {
+		return 0, fmt.Errorf("seek failed: %s", ErrClosed)
+	}
 	return fi.mod.Seek(offset, whence)
 }
 
 // Write At writes the given bytes at the offset 'at'
 func (fi *fileDescriptor) WriteAt(b []byte, at int64) (int, error) {
-	if fi.perms == OpenReadOnly {
-		return 0, fmt.Errorf("cannot write on not writeable descriptor")
+	if err := fi.checkWrite(); err != nil {
+		return 0, fmt.Errorf("write-at failed: %s", err)
 	}
-	fi.hasChanges = true
+	fi.state = stateDirty
 	return fi.mod.WriteAt(b, at)
 }

file.go

@@ -26,7 +26,7 @@ type File struct {
 	// entire DAG of nodes that comprise the file.
 	// TODO: Rename, there should be an explicit term for these root nodes
 	// of a particular sub-DAG that abstract an upper layer's entity.
-	node   ipld.Node
+	node ipld.Node
 
 	// Lock around the `node` that represents this file, necessary because
 	// there may be many `FileDescriptor`s operating on this `File`.
@@ -52,13 +52,25 @@ func NewFile(name string, node ipld.Node, parent parent, dserv ipld.DAGService)
 	return fi, nil
 }
 
-const (
-	OpenReadOnly = iota
-	OpenWriteOnly
-	OpenReadWrite
-)
+func (fi *File) Open(flags Flags) (_ FileDescriptor, _retErr error) {
+	if flags.Write {
+		fi.desclock.Lock()
+		defer func() {
+			if _retErr != nil {
+				fi.desclock.Unlock()
+			}
+		}()
+	} else if flags.Read {
+		fi.desclock.RLock()
+		defer func() {
+			if _retErr != nil {
+				fi.desclock.Unlock()
+			}
+		}()
+	} else {
+		return nil, fmt.Errorf("file opened for neither reading nor writing")
+	}
 
-func (fi *File) Open(flags int, sync bool) (FileDescriptor, error) {
 	fi.nodeLock.RLock()
 	node := fi.node
 	fi.nodeLock.RUnlock()
@@ -86,16 +98,6 @@ func (fi *File) Open(flags int, sync bool) (FileDescriptor, error) {
 		// Ok as well.
 	}
 
-	switch flags {
-	case OpenReadOnly:
-		fi.desclock.RLock()
-	case OpenWriteOnly, OpenReadWrite:
-		fi.desclock.Lock()
-	default:
-		// TODO: support other modes
-		return nil, fmt.Errorf("mode not supported")
-	}
-
 	dmod, err := mod.NewDagModifier(context.TODO(), node, fi.dagService, chunker.DefaultSplitter)
 	// TODO: Remove the use of the `chunker` package here, add a new `NewDagModifier` in
 	// `go-unixfs` with the `DefaultSplitter` already included.
@@ -106,8 +108,7 @@ func (fi *File) Open(flags int, sync bool) (FileDescriptor, error) {
 
 	return &fileDescriptor{
 		inode: fi,
-		perms: flags,
-		sync:  sync,
+		flags: flags,
 		mod:   dmod,
 	}, nil
 }
@@ -153,7 +154,7 @@ func (fi *File) GetNode() (ipld.Node, error) {
 // a file without flushing?)
 func (fi *File) Flush() error {
 	// open the file in fullsync mode
-	fd, err := fi.Open(OpenWriteOnly, true)
+	fd, err := fi.Open(Flags{Write: true, Sync: true})
 	if err != nil {
 		return err
 	}