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function rethash = PsychComputeSHA(msg, shaId)
% hash = PsychComputeSHA(msg [, shaId='256']) -- Return the SHA hash of a string.
%
% This uses either GNU/Octave's builtin hash() function, or if that doesn't exist,
% e.g., on Matlab or old Octave versions, falls back to Java's MessageDigest
% hashing classes to do the same in a slightly less efficient way.
%
% 'msg' should be a string of which the hash should be computed and returned.
%
% 'shaId' optional string with numbers, selecting one of the supported SHA
% functions. This defaults to SHA-256, ie. shaId == '256', if omitted.
%
% Currently the following shaId's are supported by both Octave and Matlab:
% '1', '224', '256', '384', '512'
%
% Returns 'hash' as the string with the returned SHA hash.
%
% History:
% 09-Nov-2020 mk Written.
if nargin < 2 || isempty(shaId)
shaId = '256';
end
if exist('hash', 'builtin')
% Octave builtin
rethash = hash(['SHA' shaId], msg);
% Verify against Java implementation?
if 0
% Java variant also works with Octave if a JVM is installed, but the Java
% method has a tad more overhead on any system:
md = javaMethod('getInstance', 'java.security.MessageDigest', ['SHA-' shaId]);
refhash = sprintf('%2.2x', typecast(md.digest(uint8(msg)), 'uint8')');
matching = strcmp(refhash, rethash)
end
else
md = javaMethod('getInstance', 'java.security.MessageDigest', ['SHA-' shaId]);
rethash = sprintf('%2.2x', typecast(md.digest(uint8(msg)), 'uint8')');
end
return;
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