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diff --git a/util/hashtab.h b/util/hashtab.h
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+/* hashtab.h
+
+   Simple, fixed size hash table.  Darn simple.
+
+   Uses a contiguous block of memory, so you can put it in a memory mapped file very easily.
+*/
+
+/*    Copyright 2009 10gen Inc.
+ *
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+
+#pragma once
+
+#include "../stdafx.h"
+#include <map>
+
+namespace mongo {
+
+#pragma pack(1)
+
+    /* you should define:
+
+       int Key::hash() return > 0 always.
+    */
+
+    template <
+    class Key,
+    class Type
+    >
+    class HashTable : boost::noncopyable {
+    public:
+        const char *name;
+        struct Node {
+            int hash;
+            Key k;
+            Type value;
+            bool inUse() {
+                return hash != 0;
+            }
+            void setUnused() {
+                hash = 0;
+            }
+        } *nodes;
+        int n;
+        int maxChain;
+
+        int _find(const Key& k, bool& found) {
+            found = false;
+            int h = k.hash();
+            int i = h % n;
+            int start = i;
+            int chain = 0;
+            int firstNonUsed = -1;
+            while ( 1 ) {
+                if ( !nodes[i].inUse() ) {
+                    if ( firstNonUsed < 0 )
+                        firstNonUsed = i;
+                }
+
+                if ( nodes[i].hash == h && nodes[i].k == k ) {
+                    if ( chain >= 200 )
+                        out() << "warning: hashtable " << name << " long chain " << endl;
+                    found = true;
+                    return i;
+                }
+                chain++;
+                i = (i+1) % n;
+                if ( i == start ) {
+                    // shouldn't get here / defensive for infinite loops
+                    out() << "error: hashtable " << name << " is full n:" << n << endl;
+                    return -1;
+                }
+                if( chain >= maxChain ) { 
+                    if ( firstNonUsed >= 0 )
+                        return firstNonUsed;
+                    out() << "error: hashtable " << name << " max chain n:" << n << endl;
+                    return -1;
+                }
+            }
+        }
+
+    public:
+        /* buf must be all zeroes on initialization. */
+        HashTable(void *buf, int buflen, const char *_name) : name(_name) {
+            int m = sizeof(Node);
+            // out() << "hashtab init, buflen:" << buflen << " m:" << m << endl;
+            n = buflen / m;
+            if ( (n & 1) == 0 )
+                n--;
+            maxChain = (int) (n * 0.05);
+            nodes = (Node *) buf;
+
+            assert( sizeof(Node) == 628 );
+            //out() << "HashTable() " << _name << " sizeof(node):" << sizeof(Node) << " n:" << n << endl;
+        }
+
+        Type* get(const Key& k) {
+            bool found;
+            int i = _find(k, found);
+            if ( found )
+                return &nodes[i].value;
+            return 0;
+        }
+
+        void kill(const Key& k) {
+            bool found;
+            int i = _find(k, found);
+            if ( i >= 0 && found ) {
+                nodes[i].k.kill();
+                nodes[i].setUnused();
+            }
+        }
+/*
+        void drop(const Key& k) {
+            bool found;
+            int i = _find(k, found);
+            if ( i >= 0 && found ) {
+                nodes[i].setUnused();
+            }
+        }
+*/
+        /** returns false if too full */
+        bool put(const Key& k, const Type& value) {
+            bool found;
+            int i = _find(k, found);
+            if ( i < 0 )
+                return false;
+            if ( !found ) {
+                nodes[i].k = k;
+                nodes[i].hash = k.hash();
+            }
+            else {
+                assert( nodes[i].hash == k.hash() );
+            }
+            nodes[i].value = value;
+            return true;
+        }
+        
+        typedef void (*IteratorCallback)( const Key& k , Type& v );
+        
+        void iterall( IteratorCallback callback ){
+            for ( int i=0; i<n; i++ ){
+                if ( ! nodes[i].inUse() )
+                    continue;
+                callback( nodes[i].k , nodes[i].value );
+            }
+        }
+    
+    };
+
+#pragma pack()
+
+} // namespace mongo