From 5cae7eea451f2b7d65b5892e2c1dafc70f8b836e Mon Sep 17 00:00:00 2001
From: Chris Hall <chris.hall@highwayman.com>
Date: Sun, 13 Feb 2011 23:11:45 +0000
Subject: 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
---
 lib/qtime.c | 48 ++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 48 insertions(+)

(limited to 'lib/qtime.c')

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) ;
+} ;
-- 
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