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/* |
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* Arc4 random number generator for OpenBSD. |
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* Copyright 1996 David Mazieres <dm@lcs.mit.edu>. |
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* |
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* Modification and redistribution in source and binary forms is |
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* permitted provided that due credit is given to the author and the |
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* OpenBSD project (for instance by leaving this copyright notice |
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* intact). |
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*/ |
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|
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/* |
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* This code is derived from section 17.1 of Applied Cryptography, |
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* second edition, which describes a stream cipher allegedly |
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* compatible with RSA Labs "RC4" cipher (the actual description of |
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* which is a trade secret). The same algorithm is used as a stream |
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* cipher called "arcfour" in Tatu Ylonen's ssh package. |
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* |
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* Here the stream cipher has been modified always to include the time |
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* when initializing the state. That makes it impossible to |
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* regenerate the same random sequence twice, so this can't be used |
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* for encryption, but will generate good random numbers. |
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* |
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* RC4 is a registered trademark of RSA Laboratories. |
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*/ |
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|
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/* |
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* $FreeBSD: /usr/local/www/cvsroot/FreeBSD/src/lib/libc/gen/arc4random.c,v 1.10.8.1 2006/11/18 21:35:13 ache Exp $ |
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* Modified for Atheme by Jilles Tjoelker |
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* $Id: arc4random.C,v 1.1 2007-07-19 08:24:56 pippijn Exp $ |
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*/ |
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|
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#include "atheme.h" |
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|
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#ifndef HAVE_ARC4RANDOM |
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|
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struct arc4_stream |
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{ |
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unsigned char i; |
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unsigned char j; |
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unsigned char s[256]; |
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}; |
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|
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#define RANDOMDEV "/dev/urandom" |
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|
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static struct arc4_stream rs; |
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static int rs_initialized; |
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static int rs_stired; |
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static int arc4_count; |
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|
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static inline unsigned char arc4_getbyte (struct arc4_stream *); |
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static void arc4_stir (struct arc4_stream *); |
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|
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static inline void |
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arc4_init (struct arc4_stream *as) |
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{ |
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int n; |
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|
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for (n = 0; n < 256; n++) |
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as->s[n] = n; |
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as->i = 0; |
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as->j = 0; |
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} |
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|
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static inline void |
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arc4_addrandom (struct arc4_stream *as, unsigned char *dat, int datlen) |
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{ |
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int n; |
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unsigned char si; |
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|
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as->i--; |
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for (n = 0; n < 256; n++) |
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{ |
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as->i = (as->i + 1); |
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si = as->s[as->i]; |
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as->j = (as->j + si + dat[n % datlen]); |
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as->s[as->i] = as->s[as->j]; |
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as->s[as->j] = si; |
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} |
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} |
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|
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static void |
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arc4_stir (struct arc4_stream *as) |
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{ |
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int fd, n; |
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struct |
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{ |
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struct timeval tv; |
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pid_t pid; |
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unsigned char rnd[128 - sizeof (struct timeval) - sizeof (pid_t)]; |
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} |
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rdat; |
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|
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gettimeofday (&rdat.tv, NULL); |
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rdat.pid = getpid (); |
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fd = open (RANDOMDEV, O_RDONLY, 0); |
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if (fd >= 0) |
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{ |
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(void) read (fd, rdat.rnd, sizeof (rdat.rnd)); |
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close (fd); |
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} |
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/* fd < 0? Ah, what the heck. We'll just take whatever was on the |
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* stack... */ |
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|
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arc4_addrandom (as, (unsigned char *) &rdat, sizeof (rdat)); |
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|
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/* |
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* Throw away the first N bytes of output, as suggested in the |
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* paper "Weaknesses in the Key Scheduling Algorithm of RC4" |
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* by Fluher, Mantin, and Shamir. N=1024 is based on |
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* suggestions in the paper "(Not So) Random Shuffles of RC4" |
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* by Ilya Mironov. |
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*/ |
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for (n = 0; n < 1024; n++) |
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(void) arc4_getbyte (as); |
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arc4_count = 400000; |
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} |
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|
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static inline unsigned char |
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arc4_getbyte (struct arc4_stream *as) |
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{ |
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unsigned char si, sj; |
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|
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as->i = (as->i + 1); |
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si = as->s[as->i]; |
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as->j = (as->j + si); |
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sj = as->s[as->j]; |
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as->s[as->i] = sj; |
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as->s[as->j] = si; |
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|
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return (as->s[(si + sj) & 0xff]); |
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} |
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|
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static inline unsigned int |
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arc4_getword (struct arc4_stream *as) |
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{ |
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unsigned int val; |
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|
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val = arc4_getbyte (as) << 24; |
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val |= arc4_getbyte (as) << 16; |
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val |= arc4_getbyte (as) << 8; |
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val |= arc4_getbyte (as); |
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|
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return (val); |
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} |
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|
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static void |
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arc4_check_init (void) |
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{ |
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if (rs_initialized) |
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return; |
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|
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arc4_init (&rs); |
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rs_initialized = 1; |
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} |
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|
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static void |
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arc4_check_stir (void) |
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{ |
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if (!rs_stired || --arc4_count == 0) |
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{ |
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arc4_stir (&rs); |
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rs_stired = 1; |
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} |
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} |
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|
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void |
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arc4random_stir () |
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{ |
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arc4_check_init (); |
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arc4_stir (&rs); |
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} |
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|
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void |
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arc4random_addrandom (unsigned char *dat, int datlen) |
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{ |
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arc4_check_init (); |
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arc4_check_stir (); |
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arc4_addrandom (&rs, dat, datlen); |
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} |
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|
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unsigned int |
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arc4random (void) |
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{ |
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unsigned int rnd; |
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|
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arc4_check_init (); |
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arc4_check_stir (); |
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rnd = arc4_getword (&rs); |
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|
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return (rnd); |
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} |
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|
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/* vim:cinoptions=>s,e0,n0,f0,{0,}0,^0,=s,ps,t0,c3,+s,(2s,us,)20,*30,gs,hs |
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* vim:ts=8 |
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* vim:sw=8 |
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* vim:noexpandtab |
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*/ |
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|
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#endif /* !HAVE_ARC4RANDOM */ |
