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/*
* Copyright (C) 2005 Guochun Shi <gshi@ncsa.uiuc.edu>
* Copyright (C) 2005 International Business Machines Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, write to the Free Software
* Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include <lha_internal.h>
#include <strings.h>
#include <clplumbing/cl_misc.h>
#include <clplumbing/cl_log.h>
#include <clplumbing/cl_misc.h>
#include <clplumbing/Gmain_timeout.h>
#include <clplumbing/cl_random.h>
#include <clplumbing/longclock.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#ifdef HAVE_TIME_H
#include <time.h>
#endif
#include <sys/time.h>
#include <sys/times.h>
/* Used to provide seed to the random number generator */
unsigned int
cl_randseed(void)
{
char buf[16];
FILE* fs;
struct timeval tv;
const char * randdevname [] = {"/dev/urandom", "/dev/random"};
int idev;
#if 0
long horrid;
#endif
/*
* Notes, based on reading of man pages of Solaris, FreeBSD and Linux,
* and on proof-of-concept tests on Solaris and Linux (32- and 64-bit).
*
* Reminder of a subtlety: our intention is not to return a random
* number, but rather to return a random-enough seed for future
* random numbers. So don't bother trying (e.g.) "rand()" and
* "random()".
*
* /dev/random and dev/urandom seem to be a related pair. In the
* words of the song: "You can't have one without the other".
*
* /dev/random is probably the best. But it can block. The Solaris
* implementation can apparently honour "O_NONBLOCK" and "O_NDELAY".
* But can others? For this reason, I chose not to use it at present.
*
* /dev/urandom (with the "u") is also good. This doesn't block.
* But some OSes may lack it. It is tempting to detect its presence
* with autoconf and use the result in a "hash-if" here. BUT... in
* at least one OS, its presence can vary depending upon patch levels,
* so a binary/package built on an enabled machine might hit trouble
* when run on one where it is absent. (And vice versa: a build on a
* disabled machine would be unable to take advantage of it on an
* enabled machine.) Therefore always try for it at run time.
*
* "gettimeofday()" returns a random-ish number in its millisecond
* component.
*
* -- David Lee, Jan 2006
*/
/*
* Each block below is logically of the form:
* if good-feature appears present {
* try feature
* if feature worked {
* return its result
* }
* }
* -- fall through to not-quite-so-good feature --
*/
/*
* Does any of the random device names work?
*/
for (idev=0; idev < DIMOF(randdevname); ++idev) {
fs = fopen(randdevname[idev], "r");
if (fs == NULL) {
cl_log(LOG_INFO, "%s: Opening file %s failed"
, __FUNCTION__, randdevname[idev]);
}else{
if (fread(buf, 1, sizeof(buf), fs)!= sizeof(buf)){
cl_log(LOG_INFO, "%s: reading file %s failed"
, __FUNCTION__, randdevname[idev]);
fclose(fs);
}else{
fclose(fs);
return (unsigned int)cl_binary_to_int(buf, sizeof(buf));
}
}
}
/*
* Try "gettimeofday()"; use its microsecond output.
* (Might it be prudent to let, say, the seconds further adjust this,
* in case the microseconds are too predictable?)
*/
if (gettimeofday(&tv, NULL) != 0) {
cl_log(LOG_INFO, "%s: gettimeofday failed",
__FUNCTION__);
}else{
return (unsigned int) tv.tv_usec;
}
/*
* times(2) returns the number of clock ticks since
* boot. Fairly predictable, but not completely so...
*/
return (unsigned int) cl_times();
#if 0
/*
* If all else has failed, return (as a number) the address of
* something on the stack.
* Poor, but at least it has a chance of some sort of variability.
*/
horrid = (long) &tv;
return (unsigned int) horrid; /* pointer to local variable exposed */
#endif
}
static gboolean inityet = FALSE;
static void
cl_init_random(void)
{
if (inityet)
return;
inityet=TRUE;
srand(cl_randseed());
}
int
get_next_random(void)
{
if (!inityet)
cl_init_random();
return rand();
}
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