.. _utilities_compression_compression:

==================
Compressing Frames
==================

The following code block describes how to create and connect a PRBS generator to a compression engine and then on to a file writer in python:

.. code-block:: python

   import pyrogue
   import rogue.utilities.fileio

   # Create a file writer, buffer size = 1000, max file size = 1MB
   fwrite = rogue.utilities.fileio.StreamWriter()
   fwrite.setBufferSize(1000)
   fwrite.setMaxSize(1000000)

   # Create a compression instance
   comp = rogue.utilities.StreamZip()

   # Create a PRBS instance to be used as a generator
   prbs = rogue.utilities.Prbs()

   # Connect the generator to the compression engine
   prbs >> comp

   # Connect the compression engine to the file writer
   comp >> fwrite.getChannel(0)

   # Open the data file
   fwrite.open("test.dat")

   # Generate 1000 frames of PRBS data, 1000 bytes each
   for _ in range(1000):
      prbs.genFrame(1000)

   # Close the data file
   fwrite.close()

The following code shows how to connect a PRBS generator to a compression engine and then on to a StreamWriter in c++.

.. code-block:: c

   #include <rogue/utilities/Prbs.h>
   #include <rogue/utilities/StreamZip.h>
   #include <rogue/utilities/fileio/StreamWriter.h>
   #include <rogue/utilities/fileio/StreamWriterChannel.h>

   // First we create a file writer instance
   rogue::utilities::fileio::StreamWriterPtr fwrite = rogue::utilities::fileio::StreamWriterPtr::create():

   // Next we set the buffer size which controls how much data to cache in memory
   // before forming a burst write to the operating system. Larger writes help
   // in file operation performance
   fwrite->setBufferSize(10000);

   // We can also set a maximum file size for each file. If this value is non-zero
   // the passed file name will be appended with a numeric value starting from 1.
   // As the max size is reached a new file will be opened with the next index value 100MBytes
   fwrite->setMaxSize(100000000);

   // By default all frames are written, even if the incoming error field is set. You
   // can choose to ignore errored frames using the following call:
   fwrite->setDropErrors(true);

   // Create a PRBS generator
   rogue::utilities::PrbsPtr prbs = rogue::utilities::Prbs::create();

   // Create a compression block
   rogue::utilities::StreamZipPtr comp = rogue::utilities::StreamZip::create();

   // Connect prbs to file writer
   prbs >> comp;

   // Connect compression block to the stream writer
   comp >> fwrite->getChannel(0);

   // Open the data file
   fwrite->open("test.dat"):

   # Generate 1000 frames of PRBS data, 1000 bytes each
   for (i=0; i < 1000; i++ ) prbs->genFrame(1000):

   // Close the data file
   fwrite->close():