1 files changed, 61 insertions, 0 deletions
diff --git a/vespajlib/src/main/java/com/yahoo/tensor/PartialAddress.java b/vespajlib/src/main/java/com/yahoo/tensor/PartialAddress.java
new file mode 100644
index 00000000000..463b7f3e99f
--- /dev/null
+++ b/vespajlib/src/main/java/com/yahoo/tensor/PartialAddress.java
@@ -0,0 +1,61 @@
+package com.yahoo.tensor;
+
+import com.google.common.annotations.Beta;
+
+/**
+ * An address to a subset of a tensors' cells, specifying a label for some but not necessarily all of the tensors
+ * dimensions.
+ * 
+ * @author bratseth
+ */
+// Implementation notes: 
+// - These are created in inner (though not inner-most) loops so they are implemented with minimal allocation. 
+//   We also avoid non-essential error checking.
+// - We can add support for string labels later without breaking the API
+@Beta
+public class PartialAddress {
+
+    // Two arrays which contains corresponding dimension=label pairs.
+    // The sizes of these are always equal.
+    private final String[] dimensionNames;
+    private final int[] labels;
+
+    private PartialAddress(Builder builder) {
+        this.dimensionNames = builder.dimensionNames;
+        this.labels = builder.labels;
+        builder.dimensionNames = null; // invalidate builder to safely take over array ownership
+        builder.labels = null;
+    }
+    
+    /** Returns the int label of this dimension, or -1 if no label is specified for it */
+    int intLabel(String dimensionName) {
+        for (int i = 0; i < dimensionNames.length; i++)
+            if (dimensionNames[i].equals(dimensionName))
+                return labels[i];
+        return -1;
+    }
+    
+    public static class Builder {
+
+        private String[] dimensionNames;
+        private int[] labels;
+        private int index = 0;
+        
+        public Builder(int size) {
+            dimensionNames = new String[size];
+            labels = new int[size];
+        }
+        
+        public void add(String dimensionName, int label) {
+            dimensionNames[index] = dimensionName;
+            labels[index] = label;
+            index++;
+        }
+        
+        public PartialAddress build() {
+            return new PartialAddress(this);
+        }
+        
+    }
+    
+}