isencrypt - determine whether a character buffer is encrypted
cc [flag ...] file ... -lgen [library ...]
int isencrypt (const char *fbuf<b>, size_t ninbuf<b>);
isencrypt uses heuristics to determine whether a buffer of characters is
encrypted. It requires two arguments: a pointer to an array of
characters and the number of characters in the buffer.
isencrypt assumes that the file is not encrypted if all the characters in
the first block are ASCII characters. If there are non-ASCII characters
in the first ninbuf characters, isencrypt assumes that the buffer is
encrypted if the setlocale LC_CTYPE category is set to C or ascii.
If the LC_CTYPE category is set to a value other than C or ascii, then
isencrypt uses a combination of heuristics to determine if the buffer is
encrypted. If ninbuf has at least 64 characters, a chi-square test is
used to determine if the bytes in the buffer have a uniform distribution;
and isencrypt assumes the buffer is encrypted if it does. If the buffer
has less than 64 characters, a check is made for null characters and a
terminating new-line to determine whether the buffer is encrypted.
If the buffer is encrypted, 1 is returned; otherwise zero is returned.
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