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gr_packet_sink.h

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00001 /* -*- c++ -*- */
00002 /*
00003  * Copyright 2005 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 INCLUDED_GR_PACKET_SINK_H
00024 #define INCLUDED_GR_PACKET_SINK_H
00025 
00026 #include <gr_sync_block.h>
00027 #include <gr_msg_queue.h>
00028 
00029 class gr_packet_sink;
00030 typedef boost::shared_ptr<gr_packet_sink> gr_packet_sink_sptr;
00031 
00032 gr_packet_sink_sptr 
00033 gr_make_packet_sink (const std::vector<unsigned char>& sync_vector,
00034                      gr_msg_queue_sptr target_queue,
00035                      int threshold = -1                 // -1 -> use default
00036                      );
00041 class gr_packet_sink : public gr_sync_block
00042 {
00043   friend gr_packet_sink_sptr 
00044   gr_make_packet_sink (const std::vector<unsigned char>& sync_vector,
00045                        gr_msg_queue_sptr target_queue,
00046                        int threshold);
00047 
00048  private:
00049   enum state_t {STATE_SYNC_SEARCH, STATE_HAVE_SYNC, STATE_HAVE_HEADER};
00050 
00051   static const int MAX_PKT_LEN    = 4096;
00052   static const int HEADERBITLEN   = 32;
00053 
00054   gr_msg_queue_sptr  d_target_queue;            // where to send the packet when received
00055   unsigned long long d_sync_vector;             // access code to locate start of packet
00056   unsigned int       d_threshold;               // how many bits may be wrong in sync vector
00057 
00058   state_t            d_state;
00059 
00060   unsigned long long d_shift_reg;               // used to look for sync_vector
00061 
00062   unsigned int       d_header;                  // header bits
00063   int                d_headerbitlen_cnt;        // how many so far
00064 
00065   unsigned char      d_packet[MAX_PKT_LEN];     // assembled payload
00066   unsigned char      d_packet_byte;             // byte being assembled
00067   int                d_packet_byte_index;       // which bit of d_packet_byte we're working on
00068   int                d_packetlen;               // length of packet
00069   int                d_packetlen_cnt;           // how many so far
00070 
00071  protected:
00072   gr_packet_sink(const std::vector<unsigned char>& sync_vector, 
00073                  gr_msg_queue_sptr target_queue,
00074                  int threshold);
00075 
00076   void enter_search();
00077   void enter_have_sync();
00078   void enter_have_header(int payload_len);
00079   
00080   int slice(float x) { return x > 0 ? 1 : 0; }
00081 
00082   bool header_ok()
00083   {
00084     // confirm that two copies of header info are identical
00085     return ((d_header >> 16) ^ (d_header & 0xffff)) == 0;
00086   }
00087 
00088   int header_payload_len()
00089   {
00090     // header consists of two 16-bit shorts in network byte order
00091     int t = (d_header >> 16) & 0xffff;
00092     return t;
00093   }
00094 
00095  public:
00096   ~gr_packet_sink();
00097 
00098   int work(int noutput_items,
00099            gr_vector_const_void_star &input_items,
00100            gr_vector_void_star &output_items);
00101 
00102 
00104   bool carrier_sensed() const
00105   {
00106     return d_state != STATE_SYNC_SEARCH;
00107   }
00108 
00109 };
00110 
00111 #endif /* INCLUDED_GR_PACKET_SINK_H */

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