prep for signed dates

bson/bsonelement.h

@@ -365,6 +365,7 @@ namespace mongo {
             return *reinterpret_cast< const mongo::OID* >( start );
         }
 
+        /** this does not use fieldName in the comparison, just the value */
         bool operator<( const BSONElement& other ) const {
             int x = (int)canonicalType() - (int)other.canonicalType();
             if ( x < 0 ) return true;

db/jsobj.cpp

@@ -362,7 +362,7 @@ namespace mongo {
 
         switch ( l.type() ) {
         case EOO:
-        case Undefined:
+        case Undefined: // EOO and Undefined are same canonicalType
         case jstNULL:
         case MaxKey:
         case MinKey:
@@ -372,6 +372,10 @@ namespace mongo {
         case Bool:
             return *l.value() - *r.value();
         case Timestamp:
+            // unsigned compare for timestamps - note they are not really dates but (ordinal + time_t)
+            if ( l.date() < r.date() )
+                return -1;
+            return l.date() == r.date() ? 0 : 1;
         case Date:
             if ( l.date() < r.date() )
                 return -1;

util/optime.h

@@ -36,7 +36,7 @@ namespace mongo {
      */
 #pragma pack(4)
     class OpTime {
-        unsigned i;
+        unsigned i; // ordinal comes first so we can do a single 64 bit compare on little endian
         unsigned secs;
         static OpTime last;
         static OpTime skewed();