Added FileHandleAsReadSeekCloser - a ReadSeekCloser adapter to FileHandle

FileHandleAsReadSeekCloser.go

@@ -0,0 +1,48 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for details.
+package main
+
+import (
+	"bazil.org/fuse"
+)
+
+// Wraps FileHandle exposing it as ReadSeekCloser intrface
+// Concurrency: not thread safe: at most on request at a time
+type FileHandleAsReadSeekCloser struct {
+	FileHandle *FileHandle
+	Offset     int64
+}
+
+// Verify that *FileHandleAsReadSeekCloser implements ReadSeekCloser
+var _ ReadSeekCloser = (*FileHandleAsReadSeekCloser)(nil)
+
+// Creates new adapter
+func NewFileHandleAsReadSeekCloser(fileHandle *FileHandle) ReadSeekCloser {
+	return &FileHandleAsReadSeekCloser{FileHandle: fileHandle}
+}
+
+// Reads a chunk of data
+func (this *FileHandleAsReadSeekCloser) Read(buffer []byte) (int, error) {
+	resp := fuse.ReadResponse{Data: buffer}
+	err := this.FileHandle.Read(nil, &fuse.ReadRequest{Offset: this.Offset, Size: len(buffer)}, &resp)
+	this.Offset += int64(len(resp.Data))
+	return len(resp.Data), err
+}
+
+// Seeks to a given position
+func (this *FileHandleAsReadSeekCloser) Seek(pos int64) error {
+	// Note: seek is implemented as virtual operation, error checking will happen
+	// when a Read() is called after a problematic Seek()
+	this.Offset = pos
+	return nil
+}
+
+// Returns reading position
+func (this *FileHandleAsReadSeekCloser) Position() (int64, error) {
+	return this.Offset, nil
+}
+
+// Closes the underlying file handle
+func (this *FileHandleAsReadSeekCloser) Close() error {
+	return this.FileHandle.Release(nil, nil)
+}