MATLAB: Reading 64 bit words

int64

I have tried reading a binary file 64 bits at a time, and is not behaving as expecting.
I have a binary file with the word = 0xFAFAFAFA00010001, if I read it like this:
word = fread(fid,1,'uint64'), and look at hex2dec(word), the word is 0xFAFAFAFA00010000 (yes, one bit has been changed).
but if I read:
word_l = fread(fid,1,'uint64'); word_h = fread(fid,1,'uint64'), I get 0x00010001 as hex2dec(word_l) and 0xFAFAFAFA as hex2dec(word_h).
I do not know if the problem is on the read (don't think so), or the 64bit management (I think is here), but I tried doing this too:
a=hex2dec('FAFAFAFA'); 
b = hex2dec('00010001');
dec2hex(bitshift(a,32))
% Output is 0xFAFAFAFA00000000
dec2hex(b)
% Output is 0x00010001
dec2hex(bitor(bitshift(a,32),b))
% Output is 0xFAFAFAFA00010000
Is there an issue with matlab and numbers larger than 53 bits? 60 bits?

Best Answer

Try reading and keeping the type as uint64 (using the *) instead of converting to double:
word = fread(fid,1,'*uint64');
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