FILE_CHECKSUM compute hash of file

read in chunks to avoid excessive RAM use

Contents

Inputs

Outputs

Ref: https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/security/MessageDigest.html#getInstance(java.lang.String)

function hash = file_checksum(file, method)
arguments
  file (1,1) string {mustBeFile}
  method (1,1) string {mustBeNonzeroLengthText}
end

if any(method == ["sha256", "SHA256"])
  method = "SHA-256";
end

file_chunk = 10e6;  % arbitrary (bytes) didn't seem to be very sensitive for speed

inst = java.security.MessageDigest.getInstance(method);

fid = fopen(file, 'r');
assert(fid > 0, "could not open " + file)

while ~feof(fid)
  % https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/security/MessageDigest.html#update(byte)
  inst.update(fread(fid, file_chunk, '*uint8'))
end
fclose(fid);

% https://docs.oracle.com/en/java/javase/21/docs/api/java.base/java/security/MessageDigest.html#digest()
hash = typecast(inst.digest, 'uint8');

hash = string(sprintf('%.2x', hash));

end

Published with MATLAB® R2024b