1 files changed, 63 insertions, 0 deletions
diff --git a/qpid/cpp/src/qpid/cluster/WriteEstimate.cpp b/qpid/cpp/src/qpid/cluster/WriteEstimate.cpp
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+++ b/qpid/cpp/src/qpid/cluster/WriteEstimate.cpp
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+/*
+ *
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you 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.
+ *
+ */
+
+#include "WriteEstimate.h"
+#include "qpid/log/Statement.h"
+#include <boost/current_function.hpp>
+
+namespace qpid {
+namespace cluster {
+
+WriteEstimate::WriteEstimate(size_t initial)
+    : growing(true), estimate(initial) {}
+
+size_t WriteEstimate::sending(size_t buffered) {
+    // We want to send a doOutput request for enough data such
+    // that if estimate bytes are written before it is self
+    // delivered then what is left in the buffer plus the doOutput
+    // request will be estimate bytes.
+
+    size_t predictLeft = (buffered > estimate) ? buffered - estimate : 0;
+    size_t request = (estimate > predictLeft) ? estimate - predictLeft : 0;
+    return request;   
+}
+
+size_t pad(size_t value) { return value + value/2; }
+
+void WriteEstimate::delivered(size_t sent, size_t buffered) {
+    size_t wrote =  sent > buffered ? sent - buffered : 0;
+    if (wrote == 0)             // No change
+        return; 
+    if (buffered > 0) { // Buffer was over-stocked, we wrote to capacity.
+        growing = false;
+        estimate = pad(wrote); // Estimate at 1.5 write for padding.
+    }
+    else if (wrote > estimate) { // Wrote everything, buffer was under-stocked
+        if (growing)
+            estimate = std::max(estimate*2, pad(wrote)); // Grow quickly if we have not yet seen an over-stock.
+        else
+            estimate = pad(wrote);
+    }
+}
+
+}} // namespace qpid::cluster
+
+