some Random tests and helpers

3 files changed, 45 insertions, 4 deletions

diff --git a/src/mongo/platform/random.cpp b/src/mongo/platform/random.cpp
index 97bde99da4a..fabb4bf69b4 100644
--- a/src/mongo/platform/random.cpp
+++ b/src/mongo/platform/random.cpp
@@ -48,6 +48,15 @@ namespace mongo {
         return rand_r( &_seed );
     }
 #endif
+    PseudoRandom::PseudoRandom( int64_t seed ) {
+        _seed = static_cast<uint32_t>( seed );
+    }
+
+    int64_t PseudoRandom::nextInt64() {
+        int64_t a = nextInt32();
+        int64_t b = nextInt32();
+        return ( a << 32 ) | b;
+    }
 
     // --- SecureRandom ----
 
diff --git a/src/mongo/platform/random.h b/src/mongo/platform/random.h
index 38ba7684fee..fc11b725eb4 100644
--- a/src/mongo/platform/random.h
+++ b/src/mongo/platform/random.h
@@ -21,21 +21,22 @@
 
 namespace mongo {
 
+    // TODO, make this is generate 64-bit numbers
     class PseudoRandom {
     public:
-        PseudoRandom( unsigned seed )
-            : _seed( seed ) {
-        }
+        PseudoRandom( int64_t seed );
 
         int32_t nextInt32();
 
+        int64_t nextInt64();
+
         /**
          * @return a number between 0 and max
          */
         int32_t nextInt32( int32_t max ) { return nextInt32() % max; }
 
     private:
-        unsigned _seed;
+        uint32_t _seed;
     };
 
     /**
diff --git a/src/mongo/platform/random_test.cpp b/src/mongo/platform/random_test.cpp
index 0752604c5ca..c8a5444638f 100644
--- a/src/mongo/platform/random_test.cpp
+++ b/src/mongo/platform/random_test.cpp
@@ -16,11 +16,14 @@
  *    limitations under the License.
  */
 
+#include <set>
+
 #include "mongo/platform/random.h"
 
 #include "mongo/unittest/unittest.h"
 
 namespace mongo {
+
     TEST( RandomTest, Seed1 ) {
 #ifndef _WIN32
         PseudoRandom a( 12 );
@@ -32,6 +35,34 @@ namespace mongo {
 #endif
     }
 
+    TEST( RandomTest, Seed2 ) {
+        PseudoRandom a( 12 );
+        PseudoRandom b( 12 );
+
+        for ( int i = 0; i < 100; i++ ) {
+            ASSERT_EQUALS( a.nextInt64(), b.nextInt64() );
+        }
+    }
+
+    TEST( RandomTest, R1 ) {
+        PseudoRandom a( 11 );
+        std::set<int32_t> s;
+        for ( int i = 0; i < 100; i++ ) {
+            s.insert( a.nextInt32() );
+        }
+        ASSERT_EQUALS( 100U, s.size() );
+    }
+
+    TEST( RandomTest, R2 ) {
+        PseudoRandom a( 11 );
+        std::set<int64_t> s;
+        for ( int i = 0; i < 100; i++ ) {
+            s.insert( a.nextInt64() );
+        }
+        ASSERT_EQUALS( 100U, s.size() );
+    }
+
+
     TEST( RandomTest, Secure1 ) {
         SecureRandom* a = SecureRandom::create();
         SecureRandom* b = SecureRandom::create();