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//**********************************************************************
// Exp-Golomb codes
//----------------------------------------------------------------------
// 
//
//

package ExpGolomb;

import H264Types::*;


      
   //-----------------------------------------------------------
   // Helper functions
   (* noinline *)
   function Bufcount expgolomb_numbits32( Buffer inbuffer );//number of bits consumed by exp-golomb code
      Bufcount tempout = 100;
      for(Integer ii=33; ii>0; ii=ii-1)
         begin
            if(inbuffer[buffersize-fromInteger(ii)]==1'b1)
               tempout = fromInteger(ii);
         end
      return tempout;
   endfunction

   (* noinline *)
   function Bit#(33) expgolomb_codenum32( Buffer inbuffer, Bufcount egnumbits );//exp-golomb codenum calculation
      Bit#(33) tempbuffer = inbuffer[buffersize-1:buffersize-33];
      Bufcount shiftamount = 33-egnumbits;
      return (tempbuffer >> zeroExtend(shiftamount))-1;
   endfunction

   (* noinline *)
   function Bit#(32) expgolomb_unsigned32( Buffer inbuffer, Bufcount egnumbits );//unsigned exp-golomb code calculation
      Bit#(33) codenum = expgolomb_codenum32( inbuffer, egnumbits );
      return truncate(codenum);
   endfunction

   (* noinline *)
   function Bit#(32) expgolomb_signed32( Buffer inbuffer, Bufcount egnumbits );//signed exp-golomb code calculation
      Bit#(33) codenum = expgolomb_codenum32( inbuffer, egnumbits );
      Bit#(33) tempout = (codenum+1) >> 1;
      Bit#(33) tempout2 = (codenum[0]==1 ? tempout : (~tempout)+1 );
      return truncate(tempout2);
   endfunction



   (* noinline *)
   function Bufcount expgolomb_numbits( Buffer inbuffer );//number of bits consumed by exp-golomb code
      Bufcount tempout = 100;
      for(Integer ii=17; ii>0; ii=ii-1)
         begin
            if(inbuffer[buffersize-fromInteger(ii)]==1'b1)
               tempout = (fromInteger(ii)*2)-1;
         end
      return tempout;
   endfunction

   (* noinline *)
   function Bit#(17) expgolomb_codenum( Buffer inbuffer );//exp-golomb codenum calculation
      Bufcount egnumbits = expgolomb_numbits( inbuffer ) >> 1;
      Bit#(33) tempbuffer = inbuffer[buffersize-1:buffersize-33] << zeroExtend(egnumbits);
      Bit#(17) tempout = tempbuffer[32:16];
      Bufcount shiftamount = 17-egnumbits-1;
      return (tempout >> zeroExtend(shiftamount))-1;
   endfunction
   
   (* noinline *)
   function Bit#(16) expgolomb_unsigned( Buffer inbuffer );//unsigned exp-golomb code calculation
      Bit#(17) codenum = expgolomb_codenum( inbuffer );
      return truncate(codenum);
   endfunction

   (* noinline *)
   function Bit#(16) expgolomb_signed( Buffer inbuffer );//signed exp-golomb code calculation
      Bit#(17) codenum = expgolomb_codenum( inbuffer );
      Bit#(17) tempout = (codenum+1) >> 1;
      Bit#(17) tempout2 = (codenum[0]==1 ? tempout : (~tempout)+1 );
      return truncate(tempout2);
   endfunction

   (* noinline *)
   function Bit#(6) expgolomb_coded_block_pattern( Buffer inbuffer, MbType mbtype );//unsigned exp-golomb code calculation
      Bit#(6) codenum = truncate(expgolomb_codenum( inbuffer ));
      if(mbPartPredMode(mbtype,0) == Intra_4x4)
         begin
            case(codenum)
               0: return 47;
               1: return 31;
               2: return 15;
               3: return 0;
               4: return 23;
               5: return 27;
               6: return 29;
               7: return 30;
               8: return 7;
               9: return 11;
               10: return 13;
               11: return 14;
               12: return 39;
               13: return 43;
               14: return 45;
               15: return 46;
               16: return 16;
               17: return 3;
               18: return 5;
               19: return 10;
               20: return 12;
               21: return 19;
               22: return 21;
               23: return 26;
               24: return 28;
               25: return 35;
               26: return 37;
               27: return 42;
               28: return 44;
               29: return 1;
               30: return 2;
               31: return 4;
               32: return 8;
               33: return 17;
               34: return 18;
               35: return 20;
               36: return 24;
               37: return 6;
               38: return 9;
               39: return 22;
               40: return 25;
               41: return 32;
               42: return 33;
               43: return 34;
               44: return 36;
               45: return 40;
               46: return 38;
               47: return 41;
            endcase
         end
      else
         begin
            case(codenum)
               0: return 0;
               1: return 16;
               2: return 1;
               3: return 2;
               4: return 4;
               5: return 8;
               6: return 32;
               7: return 3;
               8: return 5;
               9: return 10;
               10: return 12;
               11: return 15;
               12: return 47;
               13: return 7;
               14: return 11;
               15: return 13;
               16: return 14;
               17: return 6;
               18: return 9;
               19: return 31;
               20: return 35;
               21: return 37;
               22: return 42;
               23: return 44;
               24: return 33;
               25: return 34;
               26: return 36;
               27: return 40;
               28: return 39;
               29: return 43;
               30: return 45;
               31: return 46;
               32: return 17;
               33: return 18;
               34: return 20;
               35: return 24;
               36: return 19;
               37: return 21;
               38: return 26;
               39: return 28;
               40: return 23;
               41: return 27;
               42: return 29;
               43: return 30;
               44: return 22;
               45: return 25;
               46: return 38;
               47: return 41;
            endcase
         end
   endfunction



endpackage