run_length.py

这是用python语言写的一个数字广播的信号处理工具包。利用它

#!/usr/bin/env python
#
# Copyright 2007 Free Software Foundation, Inc.
# 
# This file is part of GNU Radio
# 
# GNU Radio is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3, or (at your option)
# any later version.
# 
# GNU Radio is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
# 
# You should have received a copy of the GNU General Public License
# along with GNU Radio; see the file COPYING.  If not, write to
# the Free Software Foundation, Inc., 51 Franklin Street,
# Boston, MA 02110-1301, USA.
# 

from optparse import OptionParser
import sys

def main():
    parser = OptionParser()
    parser.add_option("-f", "--file", default=None,
                      help="Choose file to read data from.")
    (options, args) = parser.parse_args()

    if options.file == None:
        print "Must specify file to read from using '-f'."
        sys.exit(1)
    print "Using", options.file, "for data."

    f = open(options.file, 'r')
    runs = []
    count = 0
    current = 0
    bytes = 0
    bits = 0
    
    for ch in f.read():
        x = ord(ch)
        bytes = bytes + 1
        for i in range(7,-1,-1):
            bits = bits + 1
            t = (x >> i) & 0x1
            if t == current:
                count = count + 1
            else:
                if count > 0:
                    if len(runs) < count:
                        for j in range(count - len(runs)):
                            runs.append(0);
                    runs[count-1] = runs[count-1] + 1

                current = 1-current;
                count = 1

    # Deal with last run at EOF
    if len(runs) < count and count > 0:
        for j in range(count - len(runs)):
            runs.append(0);
    runs[count-1] = runs[count-1] + 1

    chk = 0
    print "Bytes read: ", bytes
    print "Bits read:  ", bits
    print
    for i in range(len(runs)):
        chk = chk + runs[i]*(i+1)
        print "Runs of length", i+1, ":", runs[i]
    print
    print "Sum of runs:", chk, "bits"
    print
    print "Maximum run length is", len(runs), "bits"

if __name__ == "__main__":
    main()