commit af6569aa7e70258340a530ca733558757879daeb
author Junxiao Shi <git@mail1.yoursunny.com> Sat Jun 14 00:01:34 2014 -0700
committer Junxiao Shi <git@mail1.yoursunny.com> Tue Jun 17 17:34:39 2014 -0700
tree acb201ccbba7083a9a8c816b0ec2d579cdf6dae3
parent 12e49466bb42ec78c53437fe4e14149750cefa82

core: unify randomization

Non-security randomizations are changed to use boost::random,
with a global random number generator.

refs #1369

Change-Id: I5000fd02f170fa47058af790e2bea767f9c65650

daemon/table/cs.cpp

diff --git a/daemon/table/cs.cpp b/daemon/table/cs.cpp
index ad666d5..f1bbb0f 100644
--- a/daemon/table/cs.cpp
+++ b/daemon/table/cs.cpp
@@ -27,11 +27,15 @@
 
 #include "cs.hpp"
 #include "core/logger.hpp"
+#include "core/random.hpp"
 #include <ndn-cxx/util/crypto.hpp>
-#include "ndn-cxx/security/signature-sha256-with-rsa.hpp"
+#include <ndn-cxx/security/signature-sha256-with-rsa.hpp>
+#include <boost/random/bernoulli_distribution.hpp>
 
-#define SKIPLIST_MAX_LAYERS 32
-#define SKIPLIST_PROBABILITY 25         // 25% (p = 1/4)
+/// max skip list layers
+static const size_t SKIPLIST_MAX_LAYERS = 32;
+/// probability for an entry in layer N to appear also in layer N+1
+static const double SKIPLIST_PROBABILITY = 0.25;
 
 NFD_LOG_INIT("ContentStore");
 
@@ -265,17 +269,15 @@
 size_t
 Cs::pickRandomLayer() const
 {
-  int layer = -1;
-  int randomValue;
-
-  do
-    {
-      layer++;
-      randomValue = rand() % 100 + 1;
+  static boost::random::bernoulli_distribution<> dist(SKIPLIST_PROBABILITY);
+  // TODO rewrite using geometry_distribution
+  size_t layer;
+  for (layer = 0; layer < SKIPLIST_MAX_LAYERS; ++layer) {
+    if (!dist(getGlobalRng())) {
+      break;
     }
-  while ((randomValue < SKIPLIST_PROBABILITY) && (layer < SKIPLIST_MAX_LAYERS));
-
-  return static_cast<size_t>(layer);
+  }
+  return layer;
 }
 
 bool