binary file operations write and read

Question

ZhG on 24 Feb 2015

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https://nl.mathworks.com/matlabcentral/answers/180081-binary-file-operations-write-and-read

Hello,

I am trying to write some 2D coordinates into a binary file. However, what I read from the file that had been writen is quite different from the original data. Details are given here.

For example, I have 45 (X,Y) points. Both X and Y are integral number less than 600. The simulation requires store each of them with two bytes (8 bits) and 2 upper bits of each byte is reserved (for X, the reserved bits are filled by .mrk which is 1 or 2; for Y, simply use 0 instead). In this case, 14 bits binary number is able to represent the maximum, 16383. I write the data in several ways:

in_tmp is structure consisted of points number (.nm), points reserved mark (.mrk) and points coordinates (.coor)

for i=1:in_tmp.nm
    x1 = dec2bin(in_tmp.coor(i,1));
    y1 = dec2bin(in_tmp.coor(i,2));
      t1 = in_tm.mrk(i);
      if(t1==1)
          t2 = '01';
          t2b = 1;
      elseif(t1==2)
          t2 = '10';
          t2b = 2;
      end
      lenx = 16-length(x1);
      leny = 16-length(y1);
      x1hl = strcat(t2, '00000000000000');   % High and low
      y1hl = '0000000000000000';
      x1a = strcat(x1hl(1:lenx), num2str(x1));
      y1a = strcat(y1hl(1:leny), num2str(y1));
      y1a(1:2) = '00';
%     x1b = in_tmp.coor(i,1);
%     y1b = in_tmp.coor(i,2);
%     fwrite(fp1, t2b, 'ubit2');
%     fwrite(fp1, x1b, 'ubit14');
%     
%     fwrite(fp1, 0, 'ubit2');
%     fwrite(fp1, y1b, 'ubit14');
      fwrite(fp1, bin2dec(x1a), 'uint16');
      fwrite(fp1, bin2dec(y1a), 'uint16');
%     fwrite(fp1, bin2dec(x1a(1:8)), 'uint8');
%     fwrite(fp1, bin2dec(x1a(9:end)), 'uint8');
%     fwrite(fp1, bin2dec(y1a(1:8)), 'uint8');
%     fwrite(fp1, bin2dec(y1a(9:end)), 'uint8');
%     x1c = in_tmp.coor(i,1);
%     y1c = in_tmp.coor(i,2);
%     
%     x1hex = dec2hex(x1c);
%     y1hex = dec2hex(y1c);
%     if(length(x1hex)>2)
%         x1h = x1hex(1:end-2);
%         x1l = x1hex(end-1:end);
%     else
%         x1h = dec2hex(0);
%         x1l = x1hex;
%     end
%     
%     tx1h = dec2bin(hex2dec(x1h));
%     l1 = length(tx1h);
%     bin0 = dec2bin(128);    % '10000000'
%     if(t1==1)
%         bin0(end-l1+1:end) = tx1h;
%         bin0(1)=0;
%         bin0(2)=1;
%         
%     elseif(t1==2)
%         bin0(end-l1+1:end) = tx1h;
%     end
%     x1h = bin2dec(tx1h);
%     
%         if(length(y1hex)>2)
%         y1h = y1hex(1:end-2);
%         y1l = y1hex(end-1:end);
%     else
%         y1h = dec2hex(0);
%         y1l = y1hex;
%     end
%     fwrite(fp1, x1h, 'uint8');
%     fwrite(fp1, hex2dec(x1l), 'uint8');
%     fwrite(fp1, hex2dec(y1h), 'uint8');
%     fwrite(fp1, hex2dec(y1l), 'uint8');
end

The way I read it

for i=1:mt.nm              % nm points.
    mred(i,6) = fread(fp1, 1, 'uint8');       % Raw X coordinates.
    mred(i,7) = fread(fp1, 1, 'uint8');       % upper 2 bits are reserved info.
    tmpx = [dec2bin(mred(i,6)), dec2bin(mred(i,7))];
    if(length(tmpx)==16)
        mred(i,4) = bin2dec(tmpx(1:2));       % Real Mark.
        mred(i,1) = bin2dec(tmpx(3:end));     % Real X.
    elseif(length(tmpx)==15)
        mred(i,4) = bin2dec(tmpx(1));         % Real Type.
        mred(i,1) = bin2dec(tmpx(2:end));     % Real X.
    else
        mred(i,4) = bin2dec(tmpx(1:2));       % Type unknown.
        mred(i,1) = bin2dec(tmpx(3:end));     % Real X.
    end       
      mred(i,8) = fread(fp1, 1, 'uint8');       % Y coordinates.
      mred(i,9) = fread(fp1, 1, 'uint8');       % upper 2 bits are reserved.
      tmpy = [dec2bin(mred(i,8)), dec2bin(mred(i,9))];
      if(length(tmpy)==16)
          mred(i,10) = bin2dec(tmpy(1:2));      % Real reserved.
          mred(i,2) = bin2dec(tmpy(3:end));     % Real Y.
      elseif(length(tmpy)==15)
          mred(i,10) = bin2dec(tmpy(1));        % Real reserved.
          mred(i,2) = bin2dec(tmpy(2:end));     % Real Y.
      else
          mred(i,10) = -1;                      % Reserved unknown.
          mred(i,2) = bin2dec(tmpy);            % Real Y.
      end               
end

The read() function works well for a given software which is implemented via C++. The software generates coordinates series in such a format. Then, I prepare a read() to get the information in the binary file generated by C++ software. Then, I want to implement the write() with Matlab in that format, but the read() fails to obtain what I had written to the binary file. Anybody help? Thanks.