Integrate non-blocking XML parser as Netty codec (netty#2806)

Motivation:
Provide non-blocking XML parser as Netty codec.

Modifications:
New codec implemented/extracted.

io.netty.handler.codec.xml.XmlDecoder decodes XML fed by Netty without blocking.

Result:
Non-blocking XML stream parsing.

NOTICE.txt

@@ -195,3 +195,11 @@ can be obtained at:
   * HOMEPAGE:
     * http://logging.apache.org/log4j/
 
+This product optionally depends on 'Aalto XML', an ultra-high performance
+non-blocking XML processor, which can be obtained at:
+
+  * LICENSE:
+    * license/LICENSE.aalto-xml.txt (Apache License 2.0)
+  * HOMEPAGE:
+    * http://wiki.fasterxml.com/AaltoHome
+

codec-xml/pom.xml

@@ -0,0 +1,48 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+  ~ Copyright 2014 The Netty Project
+  ~
+  ~ The Netty Project 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.
+  -->
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
+
+  <modelVersion>4.0.0</modelVersion>
+  <parent>
+    <groupId>io.netty</groupId>
+    <artifactId>netty-parent</artifactId>
+    <version>5.0.0.Alpha2-SNAPSHOT</version>
+  </parent>
+
+  <artifactId>netty-codec-xml</artifactId>
+  <packaging>jar</packaging>
+
+  <name>Netty/Codec/XML</name>
+
+  <dependencies>
+    <dependency>
+      <groupId>${project.groupId}</groupId>
+      <artifactId>netty-codec</artifactId>
+      <version>${project.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>${project.groupId}</groupId>
+      <artifactId>netty-handler</artifactId>
+      <version>${project.version}</version>
+    </dependency>
+    <dependency>
+      <groupId>com.fasterxml</groupId>
+      <artifactId>aalto-xml</artifactId>
+    </dependency>
+  </dependencies>
+</project>
+

codec-xml/src/main/java/io/netty/handler/codec/xml/XmlAttribute.java

@@ -0,0 +1,94 @@
+/*
+ * Copyright 2014 The Netty Project
+ *
+ * The Netty Project 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.
+ */
+package io.netty.handler.codec.xml;
+
+
+/**
+ * XML attributes, it is part of {@link XmlElement}
+ */
+public class XmlAttribute {
+
+    private final String type;
+    private final String name;
+    private final String prefix;
+    private final String namespace;
+    private final String value;
+
+    public XmlAttribute(String type, String name, String prefix, String namespace, String value) {
+        this.type = type;
+        this.name = name;
+        this.prefix = prefix;
+        this.namespace = namespace;
+        this.value = value;
+    }
+
+    public String type() {
+        return type;
+    }
+
+    public String name() {
+        return name;
+    }
+
+    public String prefix() {
+        return prefix;
+    }
+
+    public String namespace() {
+        return namespace;
+    }
+
+    public String value() {
+        return value;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) { return true; }
+        if (o == null || getClass() != o.getClass()) { return false; }
+
+        XmlAttribute that = (XmlAttribute) o;
+
+        if (!name.equals(that.name)) { return false; }
+        if (namespace != null ? !namespace.equals(that.namespace) : that.namespace != null) { return false; }
+        if (prefix != null ? !prefix.equals(that.prefix) : that.prefix != null) { return false; }
+        if (type != null ? !type.equals(that.type) : that.type != null) { return false; }
+        if (value != null ? !value.equals(that.value) : that.value != null) { return false; }
+
+        return true;
+    }
+
+    @Override
+    public int hashCode() {
+        int result = type != null ? type.hashCode() : 0;
+        result = 31 * result + name.hashCode();
+        result = 31 * result + (prefix != null ? prefix.hashCode() : 0);
+        result = 31 * result + (namespace != null ? namespace.hashCode() : 0);
+        result = 31 * result + (value != null ? value.hashCode() : 0);
+        return result;
+    }
+
+    @Override
+    public String toString() {
+        return "XmlAttribute{" +
+                "type='" + type + '\'' +
+                ", name='" + name + '\'' +
+                ", prefix='" + prefix + '\'' +
+                ", namespace='" + namespace + '\'' +
+                ", value='" + value + '\'' +
+                '}';
+    }
+}

codec-xml/src/main/java/io/netty/handler/codec/xml/XmlCdata.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2014 The Netty Project
+ *
+ * The Netty Project 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.
+ */
+package io.netty.handler.codec.xml;
+
+/**
+ * XML CDATA ... <![CDATA[&lt;sender&gt;John Smith&lt;/sender&gt;]]>
+ */
+public class XmlCdata extends XmlContent {
+
+    public XmlCdata(String data) {
+        super(data);
+    }
+
+}

codec-xml/src/main/java/io/netty/handler/codec/xml/XmlCharacters.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2014 The Netty Project
+ *
+ * The Netty Project 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.
+ */
+package io.netty.handler.codec.xml;
+
+/**
+ * XML characters, e.g. <test>characters</test>, but not CDATA.
+ */
+public class XmlCharacters extends XmlContent {
+
+    public XmlCharacters(String data) {
+        super(data);
+    }
+
+}

codec-xml/src/main/java/io/netty/handler/codec/xml/XmlComment.java

@@ -0,0 +1,27 @@
+/*
+ * Copyright 2014 The Netty Project
+ *
+ * The Netty Project 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.
+ */
+package io.netty.handler.codec.xml;
+
+/**
+ * XML Comment
+ */
+public class XmlComment extends XmlContent {
+
+    public XmlComment(String data) {
+        super(data);
+    }
+
+}

codec-xml/src/main/java/io/netty/handler/codec/xml/XmlContent.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright 2014 The Netty Project
+ *
+ * The Netty Project 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.
+ */
+package io.netty.handler.codec.xml;
+
+/**
+ * XML Content is base class for XML CDATA, Comments, Characters and Space
+ */
+public abstract class XmlContent {
+
+    private final String data;
+
+    protected XmlContent(String data) {
+        this.data = data;
+    }
+
+    public String data() {
+        return data;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) { return true; }
+        if (o == null || getClass() != o.getClass()) { return false; }
+
+        XmlContent that = (XmlContent) o;
+
+        if (data != null ? !data.equals(that.data) : that.data != null) { return false; }
+
+        return true;
+    }
+
+    @Override
+    public int hashCode() {
+        return data != null ? data.hashCode() : 0;
+    }
+
+    @Override
+    public String toString() {
+        return "XmlContent{" +
+                "data='" + data + '\'' +
+                '}';
+    }
+}

codec-xml/src/main/java/io/netty/handler/codec/xml/XmlDTD.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2014 The Netty Project
+ *
+ * The Netty Project 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.
+ */
+package io.netty.handler.codec.xml;
+
+/**
+ * DTD (Document Type Definition)
+ */
+public class XmlDTD {
+
+    private final String text;
+
+    public XmlDTD(String text) {
+        this.text = text;
+    }
+
+    public String text() {
+        return text;
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) { return true; }
+        if (o == null || getClass() != o.getClass()) { return false; }
+
+        XmlDTD xmlDTD = (XmlDTD) o;
+
+        if (text != null ? !text.equals(xmlDTD.text) : xmlDTD.text != null) { return false; }
+
+        return true;
+    }
+
+    @Override
+    public int hashCode() {
+        return text != null ? text.hashCode() : 0;
+    }
+
+    @Override
+    public String toString() {
+        return "XmlDTD{" +
+                "text='" + text + '\'' +
+                '}';
+    }
+
+}