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Diffstat (limited to 'lib/clplumbing/cl_random.c')
| -rw-r--r-- | lib/clplumbing/cl_random.c | 164 |
1 files changed, 164 insertions, 0 deletions
diff --git a/lib/clplumbing/cl_random.c b/lib/clplumbing/cl_random.c new file mode 100644 index 0000000..4bafcfe --- /dev/null +++ b/lib/clplumbing/cl_random.c @@ -0,0 +1,164 @@ +/* + * 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(); +} |