1 files changed, 65 insertions, 0 deletions
diff --git a/src/main/java/com/seaofnodes/simple/util/IntHashMap.java b/src/main/java/com/seaofnodes/simple/util/IntHashMap.java
new file mode 100644
index 00000000..55aaa9f9
--- /dev/null
+++ b/src/main/java/com/seaofnodes/simple/util/IntHashMap.java
@@ -0,0 +1,65 @@
+package com.seaofnodes.simple.util;
+
+import java.util.Arrays;
+
+// Int-Int Hash Map
+public class IntHashMap {
+    private int[] _es;
+    private int _size;
+    private final int _sentinel;
+
+    // Pick a sentinel value; not allowed for keys or values.  Sentinel is
+    // returned on a miss.  Writing sentinel counts as a remove.
+    public IntHashMap(int sentinel) {
+        _sentinel = sentinel;
+        _es = new int[4];
+        Arrays.fill(_es,sentinel);
+    }
+
+    public int size() { return _size; }
+    public void clear() {
+        _size = 0;
+        Arrays.fill(_es,_sentinel);
+    }
+
+    private int cap() { return _es.length>>1; }
+
+    public int put( int key, int val ) {
+        int slot = probe(key);
+        int old = _es[(slot<<1)+1];
+        if( old == _sentinel && val != _sentinel ) _size++;
+        if( old != _sentinel && val == _sentinel ) _size--;
+        // Check cap
+        if( _size > ((cap()>>1) + (cap()>>2)) ) {
+            grow();
+            slot = probe(key);
+        }
+
+        _es[ slot<<1   ] = key;
+        _es[(slot<<1)+1] = val;
+        return old;
+    }
+
+    public int get( int key ) {
+        int slot = probe(key);
+        return _es[(slot<<1)+1];
+    }
+
+    int probe( int key ) {
+        int mask = cap()-1;
+        int slot = key & mask;
+        while( _es[slot<<1] != _sentinel && _es[slot<<1] != key )
+            slot = (slot + (key|1)) & mask;
+        return slot;
+    }
+
+    // Double underlying array size
+    private void grow() {
+        int[] old = _es;
+        _es = new int[_es.length<<1];
+        Arrays.fill(_es,_sentinel);
+        for( int i=0; i<old.length; i+=2 )
+            if( old[i] != _sentinel )
+                put(old[i],old[i+1]);
+    }
+}