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R11173/v2p5/TDMS_processLeadIn.m
61de603d20bcInterface-2.0

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TDMS_processLeadIn.m
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function [flags,info,eof_error] = TDMS_processLeadIn(fid,lastLetter)
%TDMS_processLeadIn Reads the "Lead In" portion of the data segment
%
% [flags,info] = TDMS_processLeadIn(fid)
%
% OUTPUTS
% ===============================
% flags (struct) :
% .hasMetaData - true if segment has meta data
% .kTocNewObjList - true if there is a new object order for raw data
% .hasRawData - true if segment has raw data
% .isInterleaved - true if raw data is interleaved
% .isBigEndian - true if bigEndian
% .hasRawDaqMX - true if DaqMX raw data is present
% info (struct) :
% .verNumber - ill defined, current versions should have no
% impact on the ability to read the file according
% to current specifications (Jan 2010), i.e. no
% processing change is needed if the version is one
% or the other
% .segLength - length to the next segment in bytes (after lead in)
% .metaLength - length of meta data in bytes
%LEAD IN PROCESSING
%================================================
%1) TDSm - (indicats lead in)
Ttag = fread(fid,1,'uint8');
Dtag = fread(fid,1,'uint8');
Stag = fread(fid,1,'uint8');
mtag = fread(fid,1,'uint8');
if ~(Ttag == 84 && Dtag == 68 && Stag == 83 && mtag == lastLetter)
error('Unexpected lead in header')
else
%2) Kind of Data
tocMask = fread(fid,1,'uint32');
flags = struct(...
'hasMetaData', bitget(tocMask,2),...
'kTocNewObjList', bitget(tocMask,3),...
'hasRawData', bitget(tocMask,4),...
'isInterleaved', bitget(tocMask,6),... %false, contiguous
'isBigEndian', bitget(tocMask,7),... %false, little-endian
'hasRawDaqMX', bitget(tocMask,8));
if flags.isBigEndian
error('Currently code is unable to handle Big-Endian format')
end
if flags.hasRawDaqMX
error('Currently code is unable to ignore/handle Raw Daq MX data')
end
%3) Version Number
info = struct(...
'verNumber', fread(fid,1,'uint32'),... %This is not very well defined
'segLength', fread(fid,1,'uint64'),...
'metaLength', fread(fid,1,'uint64'));
%NOT THROWING THIS ERROR RIGHT NOW
%======================================================================
%This should really quit instead of throwing an error
eof_error = info.segLength == 2^64-1;
% if info.segLength == 2^64-1
% error('File got corrupted when saving')
% end
%This most likely suggests an error in the reading
if ~eof_error && flags.hasMetaData ~= (info.metaLength ~= 0)
error('Flags suggest presence of meta data but no meta is present according to length value')
end
end
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