add OID::initSequential

1 files changed, 22 insertions, 0 deletions

diff --git a/src/mongo/bson/oid.cpp b/src/mongo/bson/oid.cpp
index fb7d6ead891..4f25fef6085 100644
--- a/src/mongo/bson/oid.cpp
+++ b/src/mongo/bson/oid.cpp
@@ -19,6 +19,7 @@
 
 #include <boost/functional/hash.hpp>
 
+#include "mongo/platform/atomic_uint64.h"
 #include "mongo/bson/bsonobjbuilder.h"
 #include "mongo/bson/oid.h"
 #include "mongo/bson/util/atomic_int.h"
@@ -135,6 +136,27 @@ namespace mongo {
         }
     }
 
+    void OID::initSequential() {
+        static AtomicUInt64 sequence;
+
+        {
+            unsigned t = (unsigned) time(0);
+            unsigned char *T = (unsigned char *) &t;
+            _time[0] = T[3]; // big endian order because we use memcmp() to compare OID's
+            _time[1] = T[2];
+            _time[2] = T[1];
+            _time[3] = T[0];
+        }
+        
+        {
+            unsigned long long nextNumber = sequence.fetchAndAdd();
+            unsigned char* numberData = reinterpret_cast<unsigned char*>(&nextNumber);
+            for ( int i=0; i<8; i++ ) {
+                data[4+i] = numberData[7-i];
+            }
+        }
+    }
+
     void OID::init( string s ) {
         verify( s.size() == 24 );
         const char *p = s.c_str();