add a portable data hash function

jdatahash.m

@@ -0,0 +1,49 @@
+function key = jdatahash(data, algorithm, varargin)
+%
+%    key = jdatahash(data)
+%        or
+%    key = jdatahash(data, algorithm)
+%
+%    computing the hash key for a string or a numeric array (data elements
+%    are serialized in the row-major order first)
+%
+%    author: Qianqian Fang (q.fang <at> neu.edu)
+%
+%    input:
+%        data: a string or a numeric array
+%        algorithm: a string denoting the data hashing algorithm (case
+%              insensitive); default is 'sha256'; supported options include
+%
+%        for both MATLAB/Octave: 'sha256' (default), 'sha1', 'md5'
+%        Octave-only: 'md2', 'md4', 'sha224', 'sha384', 'sha512'
+%
+%    examples:
+%        jdatahash('neurojson')
+%        key = jdatahash('reusable data', 'md5')
+%
+%    license:
+%        BSD or GPL version 3, see LICENSE_{BSD,GPLv3}.txt files for details
+%
+% -- this function is part of JSONLab toolbox (http://iso2mesh.sf.net/cgi-bin/index.cgi?jsonlab)
+%
+
+if(nargin < 2)
+    algorithm = 'sha-256';
+end
+
+if (ischar(data))
+    data = uint8(data);
+end
+
+opt=varargin2struct(varargin{:});
+
+if(jsonopt(opt))
+data = permute(data, ndims(data):-1:1);
+
+if(isoctavemesh && exist('hash'))
+    algorithm(algorithm=='-')=[];
+    key = hash(algorithm, char(typecast(data(:).', 'uint8')));
+else
+    md = java.security.MessageDigest.getInstance(algorithm);
+    key = sprintf('%2.2x', typecast(md.digest(typecast(data(:), 'uint8')), 'uint8')');
+end