Add split_stream, split_file

edosl0util/merge.py

-import io
 import sys
 import logging
 from datetime import datetime
@@ -88,3 +87,8 @@ def merge(streams, output=sys.stdout):
                 streams.remove(stream)
                 LOG.debug("end-of-stream %s", stream)
                 continue
+
+
+def merge_files(filepaths, destpath):
+    streams = (PacketStream(open(f)) for f in filepaths)
+    merge(streams, output=open(destpath, 'wb'))

edosl0util/split.py

+import os
 import array
+from datetime import datetime
 
 from edosl0util.timecode import unixtime
 from edosl0util.stream import PacketStream
 
 
-def split(fobj, minutes):
-    """Split a VIIRS L0 PDS file into files based on their scan time mod the
-    number of minutes provided.
+def split_stream(fobj, minutes):
+    """Split a VIIRS L0 PDS data stream into data blobs based on their scan
+    time mod the number of minutes provided.
+
+    :param fobj: A file-like object
+    :param minutes: integer number of minutes
     """
     buf = array.array('B')  # buffer for a single data file until it is written
     cur_bucket = 0  # cur time bucket of size 'minutes'
@@ -34,4 +39,44 @@ def split(fobj, minutes):
         pkt_count += 1
 
     offset = fobj.tell() - original_offset
-    yield cur_bucket, offset, pkt_count, buf.tostring()
\ No newline at end of file
+    yield cur_bucket, offset, pkt_count, buf.tostring()
+
+
+def _replace_pdsname_stamp(filename, stamp):
+    # P1570769AAAAAAAAAAAAAS15208032721000.PDS
+    pat = '{}{}{}'.format(filename[:22],
+                          '%y%j%H%M%S',
+                          filename[-7:])
+    return stamp.strftime(pat)
+
+
+def split_file(filepath, minutes, destdir):
+    """
+    Split a level0 PDS file into X minutes files by filename.
+
+    :param filepath: Path to a Level0 PDS file. It is assumed the file as a
+        standard level 0 PDS filename.
+    :param minutes: Number of minutes per bucket. Buckets always start at the
+        top of the hour. For example, a bucket size of 6 will create 10 6-min
+        buckets starting at minutes 0, 6, 12, etc ...
+    :param destdir: Where the output files are to be written. NOTE: it is likely
+        there will be filename collisions between time-based files and generated
+        files, so make sure `destdir` does not contain a time-base input file.
+
+    :raises RuntimeError: If a file exists with the same name of a bucket file.
+    """
+    destdir = destdir or '.'
+    stream = split_stream(open(filepath), minutes)
+    for timestamp, offset, pkts, blob in stream:
+        stamp = datetime.utcfromtimestamp(timestamp)
+        dirname, filename = os.path.split(filepath)
+        newname = _replace_pdsname_stamp(filename, stamp)
+        dstpath = os.path.join(dirname, destdir, newname)
+        if os.path.exists(dstpath):
+            raise RuntimeError(
+                ('File already exists. '
+                 'Bucket file possibly colliding with input file.'),
+                dstpath)
+        with open(dstpath, 'wb') as fptr:
+            fptr.write(blob)
+        yield stamp, fptr.name