Dynamic memory allocation in C

[neo_philiac]

Hello all I have this unique problem that I cant figure out. I am trying to rewrite this script in c from a matlab code. In the function I have this:



function [nbBytes, matlabType] = convertType(tiffType)
switch (tiffType)
case 1
nbBytes=1;
matlabType='uint8';
case 2
nbBytes=1;
matlabType='uchar';
case 3
nbBytes=2;
matlabType='uint16';
case 4
nbBytes=4;
matlabType='uint32';
case 5
nbBytes=8;
matlabType='uint32';
case 11
nbBytes=4;
matlabType='float32';
case 12
nbBytes=8;
matlabType='float64';
otherwise
error('tiff type %i not supported', tiffType)
end
return;

%===================sub-functions that reads an IFD entry:===================

function entry = readIFDentry()

global TIF;
entry.tiffType = fread(TIF.file, 1, 'uint16', TIF.BOS);
entry.cnt = fread(TIF.file, 1, 'uint32', TIF.BOS);
disp(['tiffType =', num2str(entry.tiffType),', cnt = ',num2str(entry.cnt)]);

[ entry.nbBytes, entry.matlabType ] = convertType(entry.tiffType);

if entry.nbBytes * entry.cnt > 4
%next field contains an offset:
offset = fread(TIF.file, 1, 'uint32', TIF.BOS);
%disp(strcat('offset = ', num2str(offset)));
fseek(TIF.file, offset, -1);
end

if TIF.entry_tag == 33629 %special metamorph 'rationals'
entry.val = fread(TIF.file, 6*entry.cnt, entry.matlabType, TIF.BOS)
else
if entry.tiffType == 5
entry.val = fread(TIF.file, 2*entry.cnt, entry.matlabType, TIF.BOS);
disp(strcat('Val 1 = ', num2str(entry.val)));
else
entry.val = fread(TIF.file, entry.cnt, entry.matlabType, TIF.BOS)
disp(strcat('Val 2 = ', num2str(entry.val)));
end
end
if ( entry.tiffType == 2 ); entry.val = char(entry.val');end

return;



You can see how for every entry we read, we get a cnt and type and depending on the type we fread certain number of bytes into dynamically allocated memory into the same variable entry.val. This is the problem in c is that how do I read the data (cnt*n) into the memory ? If I just difine entry.val as long, I get seg fault. Please help

P.S. If you need to take a look at the entire matlab code, here it is.

http://www.cytosim.org/other/tiffread.m

Thanks.