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VrSkippingSink.h

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00001 /* -*- Mode: c++ -*- */
00002 /*
00003  * Copyright 2001 Free Software Foundation, Inc.
00004  * 
00005  * This file is part of GNU Radio
00006  * 
00007  * GNU Radio is free software; you can redistribute it and/or modify
00008  * it under the terms of the GNU General Public License as published by
00009  * the Free Software Foundation; either version 2, or (at your option)
00010  * any later version.
00011  * 
00012  * GNU Radio is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00015  * GNU General Public License for more details.
00016  * 
00017  * You should have received a copy of the GNU General Public License
00018  * along with GNU Radio; see the file COPYING.  If not, write to
00019  * the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
00020  * Boston, MA 02111-1307, USA.
00021  */
00022 /*
00023  *  Copyright 1997 Massachusetts Institute of Technology
00024  * 
00025  *  Permission to use, copy, modify, distribute, and sell this software and its
00026  *  documentation for any purpose is hereby granted without fee, provided that
00027  *  the above copyright notice appear in all copies and that both that
00028  *  copyright notice and this permission notice appear in supporting
00029  *  documentation, and that the name of M.I.T. not be used in advertising or
00030  *  publicity pertaining to distribution of the software without specific,
00031  *  written prior permission.  M.I.T. makes no representations about the
00032  *  suitability of this software for any purpose.  It is provided "as is"
00033  *  without express or implied warranty.
00034  * 
00035  */
00036 
00037 
00038 #ifndef _VRSKIPPINGSINK_H_
00039 #define _VRSKIPPINGSINK_H_
00040 
00041 #include <VrSink.h>
00042 #include <stdio.h>
00043 #include <assert.h>
00044 
00045 //This sink uses a history-size chunk of data every increment units of data
00046 //  (i.e. skips over increment-history units of data)
00047 //  Each unit requested from the sink's work() procecure will operation
00048 //  on a _block_ (history-size) of data.
00049 template<class iType> 
00050 class VrSkippingSink : public VrSink<iType> {
00051 protected:
00052   unsigned int history;
00053   unsigned int increment;
00054 public: 
00055 
00056   // FIXME history and increment should be arguments to constructor
00057   
00058   VrSkippingSink() : history(1), increment(1) {
00059     setOptimalSize(1);  /*forces size of 1 to allow skipping*/
00060   }
00061 
00062   virtual void pre_initialize () {
00063     if (increment <= 0) {
00064       fprintf (stderr, "[%s:%d] initialize() invalid value for increment=%d\n",
00065                __FILE__, __LINE__, increment);
00066       abort ();
00067     }
00068 
00069     if (increment == 1){
00070       fprintf (stderr, "### Warning: increment == 1 in pre_initialize of %s.  Are you sure?\n",
00071                name ());
00072     }
00073 
00074     setSamplingFrequency(getInputSamplingFrequencyN (0) / increment);
00075   }
00076 
00077   virtual int forecast(VrSampleRange output,
00078                        VrSampleRange inputs[]);
00079 
00080   virtual float averageInputUse(int n) {
00081     if(increment>history) return (float) history/(float) increment;
00082     else return 1.0;
00083   }
00084 
00085   virtual unsigned int mapSizeUp(int i, unsigned int size) {
00086     return (unsigned int) (size * averageInputUse(i) *
00087            (getUpstreamModuleN(i)->getSamplingFrequency()
00088             /getSamplingFrequency()));
00089   }
00090 
00091   virtual ~VrSkippingSink() {}
00092 };
00093 
00094 template<class iType> int
00095 VrSkippingSink<iType>::forecast(VrSampleRange output,
00096                                 VrSampleRange inputs[]) {
00097   /* 1:history with increment skipping */
00098   /* size should always be 1 */
00099   assert (output.size == 1);
00100 
00101   for(unsigned int i=0;i<numberInputs;i++) {
00102     inputs[i].index=output.index*increment; /* ! do not subtract history ! */
00103     inputs[i].size=history;
00104   }
00105   return 0;
00106 }  
00107 
00108 #endif
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