Add first draft of code for exporting TOAST data to quasi-normal SPT3…

…G data files.

dataexport.py

@@ -0,0 +1,87 @@
+from spt3g import core
+
+def write_toast_cache_to_spt3g(data, filename, timestreams='total',
+                               verbose=False):
+    '''
+    Dump the local TOAST cache to disk in SPT3G format. Will extract data of
+    timestreams given by the timestreams argument (e.g. cache entries
+    named "total_detA" for the default timestreams value ("total") and a
+    detector "detA". If verbose is True, will also print frames to the console.
+
+    Note that this does *not* include chunks from any remote nodes. For this to
+    be useful, you *must* swizzle the data around ahead of time such that nodes
+    are chunked by time with each node holding the full set of detectors you
+    wish to include in the files. This will hopefully be improved later.
+    '''
+    writer = core.G3Writer(filename) # XXX: Multiwriter?
+
+    for obs in data.obs:
+        f = core.G3Frame(core.G3FrameType.Observation)
+        obsname = obs['name'].split('-')
+        f['SourceName'] = '-'.join(obsname[:-1])
+        f['ObservationID'] = int(obsname[-1])
+        if 'id' in obs:
+            f['ToastID'] = obs['id']
+
+        if verbose:
+            print(f)
+        writer(f)
+
+        # Loop through intervals
+        starts = [i.first for i in obs['intervals']]
+        stops = [i.last+1 for i in obs['intervals']] # 'last' is inclusive
+        intervals = sorted([(*i, True) for i in zip(starts, stops)] +
+                           [(*i, False) for i in zip(stops[:-1], starts[1:])])
+        tod = obs['tod']
+
+        times = tod.read_times()*core.G3Units.s # UNIX time
+
+        for i in intervals:
+            f = core.G3Frame(core.G3FrameType.Scan)
+            obsname = obs['name'].split('-')
+            f['SourceName'] = '-'.join(obsname[:-1])
+            f['ObservationID'] = int(obsname[-1])
+
+            if i[2]:
+                f['Selected'] = True
+
+            # Get start and stop time, skipping zero-length intervals and
+            # clamping to available data
+            start = i[0] if i[0] >= tod.local_samples[0] else \
+                    tod.local_samples[0]
+            stop = i[1] if i[1] >= tod.local_samples[0] else \
+                    tod.local_samples[0]
+            if start >= tod.local_samples[-1]:
+                continue
+            if stop >= tod.local_samples[-1]:
+                stop = tod.local_samples[-1]
+
+            startt = core.G3Time(times[start])
+            stopt = core.G3Time(times[stop])
+            if startt == stopt:
+                continue
+
+            # Boresight Az (El unavailable as of 8/7/17)
+            az = core.G3Timestream(tod.read_boresight_az()[start:stop]* \
+                 core.G3Units.rad)
+            az.start = startt
+            az.stop = stopt
+            f['BoresightAz'] = az
+
+            tsm = core.G3TimestreamMap()
+            for d in tod.local_dets: # XXX remote?
+                ts = core.G3Timestream(
+                     tod.cache.reference(timestreams + '_' + d)[start:stop],
+                     units=core.G3TimestreamUnits.Kcmb) # XXX: units?
+                ts.start = startt
+                ts.stop = stopt
+                tsm[d] = ts
+            f[timestreams] = tsm
+
+            # XXX: any other metadata we want to put in?
+            if verbose:
+                print(f)
+            writer(f)
+
+    writer(core.G3Frame(core.G3FrameType.EndProcessing))
+