gr_int32_counter_bytes_out.py

"""
Embedded Python Blocks:

Each time this file is saved, GRC will instantiate the first class it finds
to get ports and parameters of your block. The arguments to __init__  will
be the parameters. All of them are required to have default values!
"""

import numpy as np
from gnuradio import gr


class blk(gr.sync_block):  # other base classes are basic_block, decim_block, interp_block
    """int32 counter (bytes out)"""

    def __init__(self, incr=1):  # only default arguments here
        """arguments to this function show up as parameters in GRC"""
        gr.sync_block.__init__(
            self,
            name='int32 counter (bytes out)',   # will show up in GRC
            in_sig=[],
            out_sig=[np.byte]
        )
        # if an attribute with the same name as a parameter is found,
        # a callback is registered (properties work, too).
        self.incr = np.int32(incr)
        self.count = np.int32(0)
        self.leftover = bytearray()

    def work(self, input_items, output_items):
        """example: multiply with constant"""
        # we need to output `output_items` bytes
        # we already have len(self.leftover)
        # so we must add this number of integers
        # np.ceil( (output_items - len(self.leftover))/4 )
        nitems = len(output_items[0])
        ints_to_add = np.ceil( (nitems - len(self.leftover))/4 )
        
        # update working bytearray
        tmpba = np.arange(self.count, self.count+(self.incr*ints_to_add), self.incr, dtype='int32').tobytes()
        self.leftover += tmpba
        
        # assign output
        output_items[0][:] = self.leftover[0:nitems]
        
        # update book-keeping variables, count and leftover
        self.count += (self.incr * ints_to_add)
        del(self.leftover[0:nitems])
        
        # return number of items
        return len(output_items[0])