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prologdcg

SWI Prolog PIO DCGs can't deal with null bytes

I have a file that is just the letter a. I can "parse" it with this DCG:

identity([]) --> [].
identity([H|T]) --> [H], identity(T).

?- phrase_from_file(identity(X), "jah.txt").
X = [97] ;
false.

This is correct-- but when I add a NUL byte to my file:

enter image description here

When I attempt to post the above query, Prolog locks up forever. I guess it has to do something with null-terminated strings somewhere, but I'm not sure what to do here-- I'm using DCGs to parse binary files, so I need to be able to deal with null bytes.

Solution

  • I needed to pass type(binary) as an option to phrase_from_file/3.

    phrase_from_file(identity(X), "jah.txt", [type(binary)]).