## Copyright (C) 2019 Marcin Mleczko
##
## This file is free software: you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.

## -*- texinfo -*-
## @deftypefn  {} {@var{ltsRes} =} LTspice2Ovtave (@var{filename})
## This function loads simulation results created by LTspice.
##
## @var{filename} points to the '.raw' file which holds your simulation results
## in a binary data format. LTspice creates this file during simulation.
## (If your schematic lives in MySchematic.asc than your simulation results
## will end up in MySchematic.raw)
##
## @var{ltsRes} is a struct containing the data found in @var{filename}. It has
## several members with hopefully selfexplanatory names. I. e.
## varNames holds a list of net names (voltages) and current names as definend
## in the schematic in LTspice. varData_StPar1 holds the correspondig data.
##
## If a parameter sweep (.step param directive) is detected, varData_StPar1,
## varData_StPar2,.. are created, each for every swept parameter combination.
## stepParams stores a list of parameter combinations with matching indices.
##
## Currently only transient simulations (.tran) are supported. No interpolation
## or data smoothing has been implemented.
## @end deftypefn

## Author: Marcin Mleczko <address@hidden>
## Description: Load LTspice simulation results into octave workspace structure
## Version: 0.0.7

function ltsRes=LTspice2Octave(filename)

  [fid msg]=fopen(filename,'rb');
  if (fid == -1)
    error(msg);
    return;
  endif

  [buf, count] = fread(fid, 10, 'char', 0, 'ieee-le');
  if (buf(2) == 0)
    format = 'binary';
    fseek(fid,0,"bof");
   else
    format='ascii';
    error("ascii format not supported");
    fclose(fid);
    return
  end


  len_header=0;
  str_header='';

  while ( 1 )
    [buf, count] = fread(fid, 100, 'uint16=>char', 0, 'ieee-le');
    len_header=len_header+count;
    str_header=[str_header buf'];

    idx_str_Bin=strfind (str_header, 'inary');

    if (idx_str_Bin )
      len_header=idx_str_Bin+6;
      str_header=str_header(1:len_header);
      break;
    end
  end

  clear buf count;


  [s, e, te, m, ts]=regexp(str_header, "Plotname:(.*)\n",'dotexceptnewline');
  ltsRes.simType=ts{1,1}{1,1};
  clear s e te m ts;
  if ( length(strfind(ltsRes.simType, "Transient")) < 1)
    error("Only transient simulations (.tran) supported for now...");
    return;
  endif


  [s, e, te, m, ts]=regexp(str_header, "Flags:(.*)\n",'dotexceptnewline');
  ltsRes.simFlags=ts{1,1}{1,1};
  clear s e te m ts;

  if ( length(strfind(ltsRes.simFlags, "stepped"))>0)
    logfid=fopen([filename(1:end-3) "log"], "rb"); % get the step params from the log file
    logString=0;k=1;
    while ( 1 )
      logString=fgetl(logfid);
      if (length(logString) < 1) % empty line
        continue;
      elseif (logString(1) < 0) % EOF
        break;
      endif
      if (length (strfind(logString, ".step")) > 0)
        ltsRes.stepParams{1,k}=logString(6:end);
        k++;
      endif
    endwhile
    fclose(logfid);
    clear logString, k;
  else
    ltsRes.stepParams{1,1}="not a stepped simulation";
  endif

  [s, e, te, m, ts]=regexp(str_header, "No\\.\\s*Variables:(.*)\n",'dotexceptnewline');
  ltsRes.noVars=uint64(str2double(ts{1,1})-1);
  clear s e te m ts;

  [s, e, te, m, ts]=regexp(str_header, "No\\.\\s*Points:(.*)\n",'dotexceptnewline');
  ltsRes.noPts=uint64(str2double(ts{1,1})./length(ltsRes.stepParams));
  clear s e te m ts;

  [s, e, te, m, ts]=regexp(str_header, "Offset:(.*)\n",'dotexceptnewline');
  ltsRes.Offset=str2double(ts{1,1});
  clear s e te m ts;

  [s, e, te, m, ts]=regexp(str_header, "Variables:\\s*\n(.*)Binary:",'dotall');
  for k=1:1:ltsRes.noVars
    [s, e, te, m, tsVn]=regexp(ts{1,1}{1,1}, ["\n\\s*(" num2str(k) ")\\s*(\\S*)\\s*(\\S*)\\s*\n"],'dotexceptnewline','ignorecase');
    [num2str(k) " " tsVn{1,1}{1,2}];
    ltsRes.varNames{1,k}=tsVn{1,1}{1,2};
    ltsRes.varTypes{1,k}=tsVn{1,1}{1,3};
  end
  clear s e te m ts tsVn str_Header;

  bin_data_start=len_header*2;

  fseek(fid, bin_data_start,"bof");
  [ltsRes.time count]=fread (fid, ltsRes.noPts, 'double' ,4*ltsRes.noVars,'ieee-le'); ltsRes.time=abs(ltsRes.time)+ltsRes.Offset; %every var value is stored as float (= 4 bytes)

  for k=1:1:length(ltsRes.stepParams)
    for l=1:1:ltsRes.noVars
      rpos=bin_data_start+(8+4*ltsRes.noVars).*ltsRes.noPts.*(k-1) +8+4*(l-1);
      fseek(fid, rpos,"bof");
      count=uint64(0); max_frd_attps=5;
      for m=1:1:max_frd_attps
        [ltsRes.(["varData_StPar" num2str(k)])(:,l) cnt]=fread (fid, ltsRes.noPts, 'float', 4*(ltsRes.noVars-1)+8,'ieee-le');
        count=count+uint64(cnt);
        if (uint64(count) == ltsRes.noPts)
          break;
        elseif ( uint64(count) ~= ltsRes.noPts && m==max_frd_attps )
          error("not enough points read... k:%d l:%d ltsRes.noPts:%d count:%d",k, l, ltsRes.noPts, count );
        endif
      endfor
    endfor
  endfor
  fclose(fid);
  clear k l;
endfunction