'\" te
.\"  Copyright 1989 AT&T  Copyright (c) 1997, Sun Microsystems, Inc.  All Rights Reserved
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.TH ISENCRYPT 3GEN "June 18, 2021"
.SH NAME
isencrypt \- determine whether a buffer of characters is encrypted
.SH SYNOPSIS
.nf
\fBcc\fR  [\fIflag\fR]... [\fIfile\fR]... \fB-lgen\fR [\fIlibrary\fR]...
.fi

.LP
.nf
#include <libgen.h>

\fBint\fR \fBisencrypt\fR(\fBconst char *\fR\fIfbuf\fR, \fBsize_t\fR \fIninbuf\fR);
.fi

.SH DESCRIPTION
\fBisencrypt()\fR 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.
.sp
.LP
\fBisencrypt()\fR assumes that the file is not encrypted if all the characters
in the first block are \fBASCII\fR characters. If there are non-\fBASCII\fR
characters in the first \fIninbuf\fR characters, and if the \fBsetlocale()\fR
\fBLC_CTYPE\fR category is set to \fBC\fR or \fBascii\fR, \fBisencrypt()\fR
assumes that the buffer is encrypted
.sp
.LP
If the \fBLC_CTYPE\fR category is set to a value other than \fBC\fR or
\fBascii\fR, then \fBisencrypt()\fR uses a combination of heuristics to
determine if the buffer is encrypted. If \fIninbuf\fR has at least 64
characters, a chi-square test is used to determine if the bytes in the buffer
have a uniform distribution; if it does, then \fBisencrypt()\fR assumes the
buffer is encrypted.  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.
.SH RETURN VALUES
If the buffer is encrypted, \fB1\fR is returned; otherwise, zero is returned.
.SH ATTRIBUTES
See \fBattributes\fR(5) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
MT-Level	MT-Safe
.TE

.SH SEE ALSO
\fBsetlocale\fR(3C), \fBattributes\fR(5)
.SH NOTES
When compiling multithreaded applications, the \fB_REENTRANT\fR flag must be
defined on the compile line.  This flag should only be used in multithreaded
applications.