RemoteFileBuffer: try harder to avoid unnecessary flushes

fs/remote.py

@@ -71,10 +71,11 @@ class RemoteFileBuffer(object):
         self.mode = mode
         self.closed = False
         self._flushed = False
-        if hasattr(fs,"_lock"):
+        if getattr(fs,"_lock",None) is not None:
             self._lock = fs._lock.__class__()
         else:
             self._lock = threading.RLock()
+        if "r" in mode or "+" in mode:
             if rfile is not None:
                 if hasattr(rfile,"read"):
                     data = rfile.read(1024*256)
@@ -99,6 +100,7 @@ class RemoteFileBuffer(object):
         def call_with_lock(*args,**kwds):
             self._lock.acquire()
             try:
+                if "write" in name:
                     self._flushed = False
                 return a(*args,**kwds)
             finally:
@@ -130,8 +132,10 @@ class RemoteFileBuffer(object):
         try:
             self.file.flush()
             if "w" in self.mode or "a" in self.mode or "+" in self.mode:
+                if not self._flushed:
                     pos = self.file.tell()
                     self.file.seek(0)
+                    self.file.seek(0)
                     self.fs.setcontents(self.path,self.file)
                     self.file.seek(pos)
                     self._flushed = True
@@ -141,8 +145,11 @@ class RemoteFileBuffer(object):
     def close(self):
         self._lock.acquire()
         try:
+            if not self.closed:
                 self.closed = True
                 if "w" in self.mode or "a" in self.mode or "+" in self.mode:
+                    if not self._flushed:
+                        self.file.seek(0)
                         self.file.seek(0)
                         self.fs.setcontents(self.path,self.file)
                 self.file.close()