Add custom EXI buffer management

[netconf.git] / netconf / netconf-netty-util / src / main / java / org / opendaylight / netconf / nettyutil / handler / ThreadLocalSAXDecoder.java

diff --git a/netconf/netconf-netty-util/src/main/java/org/opendaylight/netconf/nettyutil/handler/ThreadLocalSAXDecoder.java b/netconf/netconf-netty-util/src/main/java/org/opendaylight/netconf/nettyutil/handler/ThreadLocalSAXDecoder.java
new file mode 100644 (file)
index 0000000..bc97b62
--- /dev/null
+++ b/netconf/netconf-netty-util/src/main/java/org/opendaylight/netconf/nettyutil/handler/ThreadLocalSAXDecoder.java
@@ -0,0 +1,47 @@
+/*
+ * Copyright (c) 2019 Pantheon Technologies, s.r.o. and others.  All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v1.0 which accompanies this distribution,
+ * and is available at http://www.eclipse.org/legal/epl-v10.html
+ */
+package org.opendaylight.netconf.nettyutil.handler;
+
+import java.io.IOException;
+import org.opendaylight.netconf.shaded.exificient.core.EXIFactory;
+import org.opendaylight.netconf.shaded.exificient.core.exceptions.EXIException;
+import org.opendaylight.netconf.shaded.exificient.main.api.sax.SAXDecoder;
+import org.xml.sax.InputSource;
+import org.xml.sax.SAXException;
+
+/**
+ * Utility SAXDecoder, which reuses a thread-local buffer during parse operations.
+ */
+final class ThreadLocalSAXDecoder extends SAXDecoder {
+    // Note these limits are number of chars, i.e. 2 bytes
+    private static final int INITIAL_SIZE = 4096;
+    private static final int CACHE_MAX_SIZE = 32768;
+    private static final ThreadLocal<char[]> CBUFFER_CACHE = ThreadLocal.withInitial(() -> new char[INITIAL_SIZE]);
+
+    ThreadLocalSAXDecoder(final EXIFactory noOptionsFactory) throws EXIException {
+        super(noOptionsFactory, null);
+    }
+
+    @Override
+    public void parse(final InputSource source) throws IOException, SAXException {
+        cbuffer = CBUFFER_CACHE.get();
+        final int startSize = cbuffer.length;
+        try {
+            super.parse(source);
+        } finally {
+            char[] toCache = cbuffer;
+            cbuffer = null;
+            if (toCache.length > CACHE_MAX_SIZE && startSize < CACHE_MAX_SIZE) {
+                // The buffer grew to large for caching, but make sure we enlarge our cached buffer to prevent
+                // some amount of reallocations in future.
+                toCache = new char[CACHE_MAX_SIZE];
+            }
+            CBUFFER_CACHE.set(toCache);
+        }
+    }
+}