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atsc_randomizer.h

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00001 /* -*- 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 #ifndef _ATSC_RANDOMIZER_H_ 00024 #define _ATSC_RANDOMIZER_H_ 00025 00026 #include <atsc_types.h> 00027 00035 class atsc_randomizer { 00036 friend class qa_atsc_randomizer; 00037 00038 public: 00039 atsc_randomizer(); 00040 00047 void reset (); 00048 00050 void randomize (atsc_mpeg_packet_no_sync &out, atsc_mpeg_packet &in); 00051 00053 void derandomize (atsc_mpeg_packet &out, atsc_mpeg_packet_no_sync &in); 00054 00055 private: 00056 static void initialize_output_map (); 00057 static unsigned char slow_output_map (int st); 00058 00059 static unsigned char fast_output_map (int st){ 00060 return output_map[(st & 0xb23c) >> 2]; // Magic const with 8 bits set improves cache 00061 // utilization. The bits correspond to the taps 00062 // used in output calculation. Others may be 00063 // safely ignored. 00064 } 00065 00067 unsigned char output (){ 00068 return fast_output_map (state); 00069 } 00070 00072 void clk (){ 00073 if (state & 0x1) 00074 state = ((state ^ mask) >> 1) | 0x8000; 00075 else 00076 state = state >> 1; 00077 } 00078 00080 unsigned char output_and_clk (){ 00081 unsigned char r = output (); 00082 clk (); 00083 return r; 00084 } 00085 00086 unsigned int state; 00087 00088 static const unsigned int preload_value = 0x018f; /* 0xf180 bit reversed */ 00089 static const unsigned int mask = 0xa638; 00090 static unsigned char output_map[1 << 14]; 00091 static bool output_map_initialized_p; 00092 }; 00093 00094 #endif /* _ATSC_RANDOMIZER_H_ */

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