Fix various DAVFS issues from issue #40

  * don't close the socket when handing off to RemoteFileBuffer
  * remove redundant check for "w" mode in the 404 case
  * properly close the socket in the isdir() case
  * add readline() method to RemoteFileBuffer

fs/contrib/davfs/__init__.py

@@ -271,16 +271,16 @@ class DAVFS(FS):
             raise_generic_error(resp,"setcontents",path)
 
     def open(self,path,mode="r"):
-        # Truncate the file if requested
         mode = mode.replace("b","").replace("t","")
+        # Truncate the file if requested
         contents = ""
         if "w" in mode:
             self.setcontents(path,contents)
         else:
             contents = self._request(path,"GET")
             if contents.status == 404:
-                # Create the file if it's missing
-                if "w" not in mode and "a" not in mode:
+                # Create the file if it's missing in append mode.
+                if "a" not in mode:
                     contents.close()
                     raise ResourceNotFoundError(path)
                 contents = ""
@@ -292,7 +292,9 @@ class DAVFS(FS):
                 contents.close()
                 raise_generic_error(contents,"open",path)
             elif self.isdir(path):
+                contents.close()
                 raise ResourceInvalidError(path)
+        #  For streaming reads, return the socket contents directly.
         if mode == "r-":
             contents.size = contents.getheader("Content-Length",None)
             if contents.size is not None:
@@ -301,11 +303,9 @@ class DAVFS(FS):
                 except ValueError:
                     contents.size = None
             return contents
-        try:
+        #  For everything else, use a RemoteFileBuffer.
+        #  This will take care of closing the socket when it's done.
         return RemoteFileBuffer(self,path,mode,contents)
-        finally:
-            if hasattr(contents,"close"):
-                contents.close()
 
     def exists(self,path):
         response = self._request(path,"PROPFIND","",{"Depth":"0"})

fs/errors.py

@@ -240,6 +240,8 @@ def convert_os_errors(func):
                 raise StorageSpaceError(opname,path=path,details=e),None,tb
             if e.errno == errno.EPERM:
                 raise PermissionDeniedError(opname,path=path,details=e),None,tb
+            if e.errno == errno.ENONET:
+                raise RemoteConnectionError(opname,path=path,details=e),None,tb
             if e.errno == errno.EACCES:
                 if sys.platform == "win32":
                     if e.args[0] and e.args[0] == 32:

fs/expose/dokan/__init__.py

@@ -170,7 +170,17 @@ def handle_fs_errors(func):
  
 
 def timeout_protect(func):
-    """Method decorator to enable timeout protection during call."""
+    """Method decorator to enable timeout protection during call.
+
+    During long-running operations, Dokan requires that the DokanResetTimeout
+    function be called periodically to indicate the progress is still being
+    made.  Unfortunately we don't have an facility for the underlying FS
+    to make these calls for us, so we have to hack around it.
+
+    The idea is to use a single background thread to monitor all active Dokan
+    method calls, checking that they haven't deadlocked and resetting the
+    appropriate timeout.
+    """
     @wraps(func)
     def wrapper(self,*args):
         info = args[-1]

fs/remote.py

@@ -159,6 +159,11 @@ class RemoteFileBuffer(object):
         self._fillbuffer()
         return self.file.__iter__()
 
+    def readline(self):
+        # TODO: implement this with on-demand loading.
+        self._fillbuffer()
+        return self.file.readline()
+        
     def _read(self, length=None):
         """Read data from the remote file into the local buffer."""
         chunklen = 1024 * 256

fs/s3fs.py

@@ -210,6 +210,7 @@ class S3FS(FS):
             if not self.isdir(dirname(path)):
                 raise ParentDirectoryMissingError(path)
             k = self._sync_set_contents(s3path,"")
+        # TODO: support streaming reads
         return RemoteFileBuffer(self,path,mode,k)
 
     def exists(self,path):