Add an XmppParser, and Stanza classes

Generate events on stanza and stream open/close.
Create Stanza and serialize them.

Note: XML namespaces are not handled yet.

src/xmpp/xmpp_stanza.hpp

@@ -0,0 +1,106 @@
+#ifndef XMPP_STANZA_INCLUDED
+# define XMPP_STANZA_INCLUDED
+
+#include <unordered_map>
+#include <string>
+#include <vector>
+
+#include <expatpp.h>
+
+/**
+ * Raised on operator[] when the attribute does not exist
+ */
+class AttributeNotFound: public std::exception
+{
+};
+
+/**
+ * Represent an XML node. It has
+ * - A parent XML node (in the case of the first-level nodes, the parent is
+     nullptr)
+ * - zero, one or more children XML nodes
+ * - A name
+ * - attributes
+ * - inner data (inside the node)
+ * - tail data (just after the node)
+ */
+class XmlNode
+{
+public:
+  explicit XmlNode(const std::string& name, XmlNode* parent);
+  explicit XmlNode(const std::string& name);
+  XmlNode(XmlNode&& node):
+    name(std::move(node.name)),
+    parent(std::move(node.parent)),
+    closed(std::move(node.closed)),
+    attributes(std::move(node.attributes)),
+    children(std::move(node.children)),
+    inner(std::move(node.inner)),
+    tail(std::move(node.tail))
+  {
+    node.parent = nullptr;
+  }
+
+  ~XmlNode();
+
+  void delete_all_children();
+  void set_attribute(const std::string& name, const std::string& value);
+  /**
+   * Set the content of the tail, that is the text just after this node
+   */
+  void set_tail(const std::string& data);
+  /**
+   * Set the content of the inner, that is the text inside this node
+   */
+  void set_inner(const std::string& data);
+  void add_child(XmlNode* child);
+  void add_child(XmlNode&& child);
+  XmlNode* get_last_child() const;
+  /**
+   * Mark this node as closed, nothing else
+   */
+  void close();
+  XmlNode* get_parent() const;
+  const std::string& get_name() const;
+  /**
+   * Serialize the stanza into a string
+   */
+  std::string to_string() const;
+  void display() const;
+  /**
+   * Whether or not this node has at least one child (if not, this is a leaf
+   * node)
+   */
+  bool has_children() const;
+  /**
+   * Gets the value for the given attribute, raises AttributeNotFound if the
+   * node as no such attribute.
+   */
+  const std::string& operator[](const std::string& name) const;
+  /**
+   * Use this to set an attribute's value, like node["id"] = "12";
+   */
+  std::string& operator[](const std::string& name);
+
+private:
+  std::string name;
+  XmlNode* parent;
+  bool closed;
+  std::unordered_map<std::string, std::string> attributes;
+  std::vector<XmlNode*> children;
+  std::string inner;
+  std::string tail;
+
+  XmlNode(const XmlNode&) = delete;
+  XmlNode& operator=(const XmlNode&) = delete;
+  XmlNode& operator=(XmlNode&&) = delete;
+};
+
+/**
+ * An XMPP stanza is just an XML node of level 2 in the XMPP document (the
+ * level 1 ones are the <stream::stream/>, and the ones about 2 are just the
+ * content of the stanzas)
+ */
+typedef XmlNode Stanza;
+
+#endif // XMPP_STANZA_INCLUDED