summaryrefslogtreecommitdiffstats
path: root/lib/qtime.c
diff options
context:
space:
mode:
authorChris Hall <chris.hall@highwayman.com>2011-02-13 23:11:45 +0000
committerChris Hall <chris.hall@highwayman.com>2011-02-13 23:11:45 +0000
commit5cae7eea451f2b7d65b5892e2c1dafc70f8b836e (patch)
tree0fbd9679e9ae28e7d061b5bdda08756077415ecb /lib/qtime.c
parent64be6d766a65dc0749d17f5023d714678e9c96a6 (diff)
downloadquagga-5cae7eea451f2b7d65b5892e2c1dafc70f8b836e.tar.bz2
quagga-5cae7eea451f2b7d65b5892e2c1dafc70f8b836e.tar.xz
Second tranche of updates for pipework branch.
modified: bgpd/bgp_connection.c modified: bgpd/bgp_debug.c modified: bgpd/bgp_engine.h modified: bgpd/bgp_main.c modified: bgpd/bgp_packet.c modified: bgpd/bgp_peer.c modified: bgpd/bgp_route.c modified: bgpd/bgp_routemap.c modified: bgpd/bgp_session.c modified: bgpd/bgp_vty.c modified: bgpd/bgpd.c modified: bgpd/bgpd.h modified: configure.ac modified: isisd/dict.h modified: isisd/isis_misc.c modified: isisd/isis_routemap.c modified: isisd/isis_spf.c modified: lib/Makefile.am modified: lib/command.c modified: lib/command.h modified: lib/command_execute.h modified: lib/command_parse.c modified: lib/command_parse.h modified: lib/command_queue.c modified: lib/command_queue.h modified: lib/elstring.h modified: lib/heap.c modified: lib/if.c modified: lib/if.h modified: lib/keychain.c modified: lib/keystroke.c modified: lib/keystroke.h modified: lib/list_util.c modified: lib/list_util.h modified: lib/log.c modified: lib/log.h modified: lib/memory.c modified: lib/memory.h modified: lib/memtypes.c modified: lib/misc.h modified: lib/mqueue.c modified: lib/mqueue.h deleted: lib/node_type.h modified: lib/pthread_safe.c modified: lib/qfstring.c modified: lib/qiovec.c modified: lib/qiovec.h modified: lib/qpath.c modified: lib/qpnexus.c modified: lib/qpnexus.h modified: lib/qpselect.c modified: lib/qpthreads.h modified: lib/qstring.c modified: lib/qstring.h modified: lib/qtime.c modified: lib/qtime.h modified: lib/qtimers.c modified: lib/qtimers.h modified: lib/routemap.c modified: lib/symtab.h modified: lib/thread.h deleted: lib/uty.h modified: lib/vector.c modified: lib/vector.h modified: lib/version.h.in modified: lib/vio_fifo.c modified: lib/vio_fifo.h modified: lib/vio_lines.c modified: lib/vio_lines.h modified: lib/vty.c modified: lib/vty.h modified: lib/vty_cli.c modified: lib/vty_cli.h modified: lib/vty_io.c modified: lib/vty_io.h modified: lib/vty_io_basic.c modified: lib/vty_io_basic.h modified: lib/vty_io_file.c modified: lib/vty_io_file.h modified: lib/vty_io_shell.c modified: lib/vty_io_term.c modified: lib/vty_io_term.h modified: lib/vty_local.h modified: lib/vty_pipe.c modified: lib/workqueue.h modified: lib/zebra.h modified: ospf6d/ospf6_lsa.c modified: ripngd/ripngd.c modified: tests/test-list_util.c modified: tests/test-vector.c modified: vtysh/vtysh.c modified: vtysh/vtysh_config.c
Diffstat (limited to 'lib/qtime.c')
-rw-r--r--lib/qtime.c48
1 files changed, 48 insertions, 0 deletions
diff --git a/lib/qtime.c b/lib/qtime.c
index 3ec34a72..92e67e27 100644
--- a/lib/qtime.c
+++ b/lib/qtime.c
@@ -192,3 +192,51 @@ qt_craft_monotonic(void) {
return (monotonic * times_scale_q) +
((monotonic * times_scale_r) / times_clk_tcks) ;
} ;
+
+/*==============================================================================
+ * A simple minded random number generator.
+ *
+ * Designed to be reasonably unpredictable... particularly the ms bits !
+ */
+
+static inline uint32_t
+qt_rand(uint64_t q, uint64_t s)
+{
+ /* Takes q ^ s and reduces to 32 bits by xoring ms and ls halves
+ * then uses Knuth recommended linear congruent to randomise that, so that
+ * most of the original bits affect the result.
+ *
+ * Note that linear congruent tends to be "more random" in the ms bits.
+ */
+ q ^= s ;
+ q = (q ^ (q >> 32)) & 0xFFFFFFFF ;
+ return ((q * 2650845021) + 5) & 0xFFFFFFFF ;
+} ;
+
+extern uint32_t
+qt_random(uint32_t seed)
+{
+ uint32_t x, y ;
+ uint64_t t ;
+
+ t = qt_get_realtime() ;
+
+ /* Set x by munging the time, the address of x, the current contents of x,
+ * and the "seed". (Munge the seed a bit for good measure.)
+ */
+ x = qt_rand(t ^ (uint64_t)x ^ (uint64_t)&x, seed ^ 3141592653) ;
+ /* munge the address and the contents with the seed */
+
+ /* Set y by munging the time, the address of y, the current contents of y,
+ * and the "seed". (Munge the seed a bit for good measure.)
+ */
+ y = qt_rand(t ^ (uint64_t)y ^ (uint64_t)&y, seed ^ 3562951413) ;
+ /* munge the current real time with the seed */
+
+ /* Return x and y munged together.
+ *
+ * Note that we swap the halves of y before munging, in order to spread
+ * the "more random" part of y down to the ls end of the result.
+ */
+ return x ^ ((y >> 16) & 0xFFFF) ^ ((y & 0xFFFF) << 16) ;
+} ;