readsample()

Tvalue datrw::pdas::readsample	(	std::istream &	is,
		const Etype &	type
	)

function to read one sample

Definition at line 182 of file pdasread.cc.

References DATRW_abort, FtypeGAINRANGED, FtypeINT, and FtypeLONG.

Referenced by countdata(), and readdata().

    {
      int invalue;
      Tvalue value;
      union Byte {
        char inchar;
        unsigned char byte;
      }; // union byte
      if (type==FtypeINT)
      {
        Byte lbyte, hbyte;
        if (is.eof()) throw FoundEOF();
        is.get(lbyte.inchar);
        if (is.eof()) throw FoundEOF();
        is.get(hbyte.inchar);
        invalue=int(lbyte.byte)+256*int(hbyte.byte);
        if (int(hbyte.byte)>127) 
        { value=Tvalue(invalue-65536); } else { value=Tvalue(invalue); }
      }
      else if (type==FtypeLONG)
      {
        union Long {
          // long int ival;
          int ival;
          char byte[4];
          unsigned char ubyte[4];
        }; // union Long
        Long inval;
        if (is.eof()) throw FoundEOF();
        is.get(inval.byte[0]);
        if (is.eof()) throw FoundEOF();
        is.get(inval.byte[1]);
        if (is.eof()) throw FoundEOF();
        is.get(inval.byte[2]);
        if (is.eof()) throw FoundEOF();
        is.get(inval.byte[3]);
        value=inval.ival;
      }
      else if (type==FtypeGAINRANGED)
      {
        // DATRW_abort("gainranged format ist not supported");
        union Short {
          short int ival;
          char byte[2];
          unsigned char ubyte[2];
        }; // union Short
        Short inval;
        if (is.eof()) throw FoundEOF();
        is.get(inval.byte[0]);
        if (is.eof()) throw FoundEOF();
        is.get(inval.byte[1]);
        Short Smantissa=inval;
        Smantissa.ubyte[0]=(inval.ubyte[0] & 0xFC);
        int mantissa=Smantissa.ival/4;
        unsigned short int exponent=(inval.ubyte[0] & 0x03);
        int shifts=(5-exponent)*3;
        int factor=(1<<shifts);
        value=mantissa*factor;
        /*
        std::cerr 
          << inval.ival << " "
          << Smantissa.ival << " "
          << mantissa << " "
          << exponent << " "
          << shifts << " "
          << factor << " "
          << value << " " << std::endl;
        */
      }
      else
      {
        DATRW_abort("ERROR: unsupported data type!"); 
      }
      return(value);
    }

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