function [floats, times] = convfloats(c, t, preCode)
% function [floats, times] = convfloats(c, t, preCode)
%
% c       The encodes in the cortex data file you would like to extract
%         floating point information from
% t       The times that the corresponding encodes were output
% preCode Optional argument that causes the program to extract only the
%         integers which follow this encoded value. This allows you to
%         "mark" different integers as having different meanings in the
%         data file.
%
% Given a set of Matlab encode values and their times,
% read out the floating point numbers and store them in the floats array,
% along with their time of occurrence. This code is used to extract
% information embedded in the data file with the routines in "extenc.h"
% and "extenc.c"
% 
% If preCode is given, then only get integers which follow
% preCode in the data. Effectively, this replaces INT_MARKER
% with preCode.
%
% Because of the way Cortex encodes things, intervening codes can be
% mixed with floating point data. You must be careful to never have
% two threads running which both try to encode floating point values,
% as the resulting data file can intermingle the bytes of two separate
% floats, making it impossible to later decode.
%
% This code needs access to either a global structure Encodes, or
% an m-file called 'encodes.m' that creates the structure.
%
% Version 1.0
% For additional code, updated versions, questions or comments, please refer
% to the Active Perception Lab home page
%            http://www.cnbc.cmu.edu/~tai/lab.html

% Copyright 1998-1999
% Rick Romero
% rickr+@cmu.edu
% Permission to use and modify is granted,
% but not to redistribute original or modified code.


% Assumes that floats are coded as follows:
% All floats are marked by a FLOAT_MARKER (125) before the float data
% The float data is encoded using four encodes, ENCODE_FLOAT[1-4] in
% increasing order of byte number.


% Some encode values, just so we have them
if (exist('Encodes') == 0)
  global Encodes
  evalin('caller','global Encodes;encodes');
end

if (nargin < 3)
  preCode = Encodes.FLOAT_MARKER;
end


c = c(:)';
t = t(:)';

which = find(c == preCode);
times = t(which);
numfloats = prod(size(which));
floats = zeros(numfloats, 1);

for i=1:numfloats
  if (i == numfloats)
    cndx = which(i):prod(size(c));
  else
    cndx = which(i):(which(i+1)-1);
  end
  cc = c(cndx);
  cencodes = find((cc >= Encodes.ENCODE_FLOAT1) & ...
                  (cc < Encodes.ENCODE_FLOAT4 + 256));
  if (prod(size(cencodes)) ~= 4)
    error('Problem reading in float data--wrong number of markers');
  end
  if ((cc(cencodes(1)) >= Encodes.ENCODE_FLOAT2) | ...
      (cc(cencodes(2)) >= Encodes.ENCODE_FLOAT3) | ...
      (cc(cencodes(3)) >= Encodes.ENCODE_FLOAT4) | ...
      (cc(cencodes(4)) <  Encodes.ENCODE_FLOAT4) | ...
      (cc(cencodes(3)) <  Encodes.ENCODE_FLOAT3) | ...
      (cc(cencodes(2)) <  Encodes.ENCODE_FLOAT2))
    errmsg =  sprintf('Out of order float data: received following encodes (0x%X 0x%X 0x%X 0x%X)', cc(cencodes(1)), cc(cencodes(2)), cc(cencodes(3)), cc(cencodes(4)));
    error(errmsg);
  end

  cencodes = cc(cencodes);
  cencodes = fliplr(bitand(cencodes, 255));
  if (cencodes(1) > 127)
    fsign = -1;
  else
    fsign = 1;
  end
  fexp = 2 * bitand(cencodes(1), 127) + bitget(cencodes(2), 8) - 127;
  if (all(cencodes == 0))
    floats(i) = 0;
  else
    fmant = 1 + bitor(...
                  bitshift(...
                    bitor(bitshift(bitand(cencodes(2), 127), 8), ...
                          cencodes(3)), 8), ...
                  cencodes(4)) / bitshift(1, 23);
    floats(i) = fsign * fmant * (2 ^ fexp);
  end
end