[ONOS-7596] Support reading table entries with counter data in P4Runtime

Change-Id: I85bacb1697a6c881dd69ba74a2162c73ec0b8aee
(cherry picked from commit 7632e150e14865c82b2e27e4cecfa44a79cf8f16)
diff --git a/core/api/src/main/java/org/onosproject/net/pi/runtime/PiCounterCell.java b/core/api/src/main/java/org/onosproject/net/pi/runtime/PiCounterCell.java
new file mode 100644
index 0000000..9508cbc
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/pi/runtime/PiCounterCell.java
@@ -0,0 +1,98 @@
+/*
+ * Copyright 2017-present Open Networking Foundation
+ *
+ * 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.
+ */
+
+package org.onosproject.net.pi.runtime;
+
+import com.google.common.annotations.Beta;
+import com.google.common.base.MoreObjects;
+import com.google.common.base.Objects;
+
+/**
+ * Counter cell of a protocol-independent pipeline.
+ */
+@Beta
+public final class PiCounterCell {
+
+    private final PiCounterCellId cellId;
+    private final PiCounterCellData counterData;
+
+    /**
+     * Creates a new counter cell for the given cell identifier and counter cell data.
+     *
+     * @param cellId  counter cell identifier
+     * @param piCounterCellData  counter cell data
+     */
+    public PiCounterCell(PiCounterCellId cellId, PiCounterCellData piCounterCellData) {
+        this.cellId = cellId;
+        this.counterData = piCounterCellData;
+    }
+
+    /**
+     * Creates a new counter cell for the given cell identifier, number of packets and bytes.
+     *
+     * @param cellId  counter cell identifier
+     * @param packets  number of packets
+     * @param bytes  number of bytes
+     */
+    public PiCounterCell(PiCounterCellId cellId, long packets, long bytes) {
+        this.cellId = cellId;
+        this.counterData = new PiCounterCellData(packets, bytes);
+    }
+
+    /**
+     * Returns the cell identifier.
+     *
+     * @return cell identifier
+     */
+    public PiCounterCellId cellId() {
+        return cellId;
+    }
+
+    /**
+     * Returns the data contained by this cell.
+     *
+     * @return counter cell data
+     */
+    public PiCounterCellData data() {
+        return counterData;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (!(o instanceof PiCounterCell)) {
+            return false;
+        }
+        PiCounterCell that = (PiCounterCell) o;
+        return Objects.equal(cellId, that.cellId) &&
+                Objects.equal(counterData, that.counterData);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hashCode(cellId, counterData);
+    }
+
+    @Override
+    public String toString() {
+        return MoreObjects.toStringHelper(this)
+                .add("cellId", cellId)
+                .add("counterData", counterData)
+                .toString();
+    }
+}