hcam.py -- updates for logging

added a set method to hcam.Rbytes, like ucam equivalent

hipercam/hcam.py

@@ -304,6 +304,7 @@ def __init__(self, fname, server=False, full=True):
             self.toff1 = self.toff2 = 1.0e-3 * E / 2.0
             self.toff3 = self.toff4 = 1.0e-3 * E
             self.tdead = 1.0e-3 * (FR + W)
+
         elif self.drift:
             # Drift mode
             LD = hd["ESO DET DRIFT TLINEDUMP"]
@@ -1380,6 +1381,12 @@ def __init__(self, fname, nframe=1, server=False):
 
         # move to the start of the timing bytes
         self.nframe = nframe
+
+        # This sets whether on the next call we should regard the file
+        # position as requiring a reset. Used by 'set' to flag up different
+        # actions in __call__
+        self.reset = False
+
         if not server:
             self._ffile.seek(
                 self._hbytes + self._framesize * self.nframe - self.ntbytes
@@ -1410,23 +1417,11 @@ def __call__(self, nframe=None):
         Returns:: the timing bytes of the frame
         """
 
-        # set the frame to be read and whether the file pointer needs to be
-        # reset
-        if nframe is None:
-            # just read whatever frame we are on
-            reset = False
-        else:
-            if nframe == 0:
-                # go for the last one
-                nframe = self.ntotal()
-
-            # update frame counter
-            reset = self.nframe != nframe
-            self.nframe = nframe
+        self.set(nframe)
 
         if self.server:
             # define command to send to server
-            if reset:
+            if self.reset:
                 # requires a seek as well as a read
                 data = json.dumps(dict(action="get_frame", frame_number=self.nframe))
             else:
@@ -1452,7 +1447,7 @@ def __call__(self, nframe=None):
 
         else:
             # find the start of the timing data if necessary
-            if reset:
+            if self.reset:
                 self._ffile.seek(
                     self._hbytes + self._framesize * self.nframe - self.ntbytes
                 )
@@ -1465,9 +1460,40 @@ def __call__(self, nframe=None):
 
         # update the internal frame counter
         self.nframe += 1
+        self.reset = False
 
         return tbytes
 
+    def set(self, nframe=1):
+        """Resets the position so that we are just about to read
+        the timing data of nframe, but does not read them unlike
+        __call__
+
+        Arguments::
+
+           nframe : int | none
+              frame number to get, starting at 1. 0 for the last (complete)
+              frame. 'None' indicates that the next frame is wanted.
+
+        Returns:: the timing bytes of the frame
+        """
+
+        old_frame = self.nframe
+
+        if nframe is None:
+            # just read whatever frame we are now on
+            self.reset = False
+        else:
+            if nframe == 0:
+                # go for the last one
+                nframe = self.ntotal()
+
+            # record whether we need to be in reset mode
+            # update frame counter
+            self.reset = self.nframe != nframe
+            self.nframe = nframe
+
+        return old_frame
 
 class Rtime(Rtbytes):
     """Callable, iterable object to generate timing data only from HiPERCAM raw data files.