Migrated source code from Simantics SVN

[simantics/platform.git] / bundles / org.simantics.scl.compiler / src / org / simantics / scl / compiler / internal / types / HashCodeUtils.java

diff --git a/bundles/org.simantics.scl.compiler/src/org/simantics/scl/compiler/internal/types/HashCodeUtils.java b/bundles/org.simantics.scl.compiler/src/org/simantics/scl/compiler/internal/types/HashCodeUtils.java
new file mode 100644 (file)
index 0000000..57a40d6
--- /dev/null
+++ b/bundles/org.simantics.scl.compiler/src/org/simantics/scl/compiler/internal/types/HashCodeUtils.java
@@ -0,0 +1,46 @@
+package org.simantics.scl.compiler.internal.types;
+
+/**
+ * Utils for computing 32-bit Murmur3 hash function
+ */
+public class HashCodeUtils {
+    
+    private static final int C1 = 0xcc9e2d51;
+    private static final int C2 = 0x1b873593;
+    private static final int R1 = 15;
+    private static final int R2 = 13;
+    private static final int M = 5;
+    private static final int N = 0xe6546b64;
+    
+    public static final int SEED = 0;
+    
+    public static int update(int hash, int value) {
+        value *= C1;
+        value = Integer.rotateLeft(value, R1);
+        value *= C2;
+        
+        hash ^= value;
+        return Integer.rotateLeft(hash, R2) * M + N;
+    }
+    
+    public static int preprocessValue(int value) {
+        value *= C1;
+        value = Integer.rotateLeft(value, R1);
+        value *= C2;
+        return value;
+    }
+    
+    public static int updateWithPreprocessedValue(int hash, int preprocessedValue) {
+        hash ^= preprocessedValue;
+        return Integer.rotateLeft(hash, R2) * M + N;
+    }
+    
+    public static int finalize(int hash) {
+        hash ^= hash >> 16;
+        hash *= 0x85ebca6b;
+        hash ^= hash >> 13;
+        hash *= 0xc2b2ae35;
+        hash ^= hash >> 16;
+        return hash;
+    }
+}