1 files changed, 78 insertions, 0 deletions
diff --git a/logserver/src/main/java/com/yahoo/logserver/handlers/replicator/FormattedBufferCache.java b/logserver/src/main/java/com/yahoo/logserver/handlers/replicator/FormattedBufferCache.java
new file mode 100644
index 00000000000..f20adbe3c91
--- /dev/null
+++ b/logserver/src/main/java/com/yahoo/logserver/handlers/replicator/FormattedBufferCache.java
@@ -0,0 +1,78 @@
+// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.logserver.handlers.replicator;
+
+import java.util.Map;
+import java.util.IdentityHashMap;
+import java.nio.ByteBuffer;
+import java.nio.charset.Charset;
+import com.yahoo.log.LogMessage;
+import com.yahoo.logserver.formatter.LogFormatter;
+import com.yahoo.logserver.formatter.LogFormatterManager;
+
+/**
+ * This class is used to cache log messages that have been
+ * formatted into ByteBuffers.  The purpose of this class
+ * is to make it easier to support multiple message formats while
+ * still ensuring we don't format more messages than we strictly need
+ * to and that we don't keep around more buffers that we ought to.
+ *
+ * <P>
+ * This is not a general purpose class, I think, so please
+ * refer to the source code of the Replicator class for
+ * information on how to use this.
+ *
+ * <P>
+ * This class is not threadsafe.
+ *
+ * @author  <a href="mailto:borud@yahoo-inc.com">Bjorn Borud</a>
+ */
+public class FormattedBufferCache {
+    // the documentation says " All of the methods defined in this
+    // class are safe for use by multiple concurrent threads." so
+    // we have only one instance of the charset for this class.
+    //
+    static private final Charset charset = Charset.forName("utf-8");
+
+    private final IdentityHashMap<LogFormatter, ByteBuffer> buffers;
+
+    public FormattedBufferCache () {
+        // hope this is a good hash size
+        int initialSize = LogFormatterManager.getFormatterNames().length * 2;
+        buffers = new IdentityHashMap<LogFormatter, ByteBuffer>(initialSize);
+    }
+
+    /**
+     * Return a ByteBuffer slice of a buffer containing the
+     * LogMessage formatted by the LogFormatter.  If one didn't
+     * exist in the cache from before, it will after this
+     * method returns.
+     *
+     * @param msg The log message you wish to format
+     * @param formatter The log formatter you wish to use for formatting
+     * @return Returns a ByteBuffer slice
+     */
+    public ByteBuffer getFormatted (LogMessage msg, LogFormatter formatter) {
+        ByteBuffer bb = buffers.get(formatter);
+        if (bb == null) {
+            bb = charset.encode(formatter.format(msg));
+            buffers.put(formatter, bb);
+        }
+        return bb.slice();
+    }
+
+    /**
+     * After we're done distributing the log message to all the
+     * clients we clear the cache so we are ready for the next
+     * message.
+     */
+    public void reset () {
+        buffers.clear();
+    }
+
+    /**
+     * This is here for test purposes.  Don't get any bright ideas.
+     */
+    public Map<LogFormatter,ByteBuffer> getUnderlyingMapOnlyForTesting() {
+        return buffers;
+    }
+}