Replace libxml2's xmlNode with a custom XML structure

The new structure (rexmpp_xml) is simpler, and should allow
manipulation from Rust without any dependency on libxml2 from the Rust
code (while Rust has its own parsers, such as rxml). Alternative XML
parsers (e.g., libexpat) now can be used from the C code.

The replacement/abstraction is not quite complete yet: the parsing
process itself (xmlParseChunk and friends) should be abstracted out.

1 files changed, 232 insertions, 0 deletions

diff --git a/src/rexmpp_xml.h b/src/rexmpp_xml.h
new file mode 100644
index 0000000..33f61f2
--- /dev/null
+++ b/src/rexmpp_xml.h
@@ -0,0 +1,232 @@
+/**
+   @file rexmpp_xml.h
+   @brief XML structures and functions for rexmpp
+   @author defanor <defanor@uberspace.net>
+   @date 2023
+   @copyright MIT license.
+*/
+
+#ifndef REXMPP_XML_H
+#define REXMPP_XML_H
+
+#include <libxml/tree.h>
+
+typedef struct rexmpp_xml_qname rexmpp_xml_qname_t;
+typedef struct rexmpp_xml_attribute rexmpp_xml_attr_t;
+typedef struct rexmpp_xml_node rexmpp_xml_t;
+
+struct rexmpp_xml_qname {
+  char *name;
+  char *namespace;
+};
+
+struct rexmpp_xml_attribute {
+  rexmpp_xml_qname_t qname;
+  char *value;
+  rexmpp_xml_attr_t *next;
+};
+
+enum rexmpp_xml_node_type {
+  REXMPP_XML_ELEMENT,
+  REXMPP_XML_TEXT
+};
+
+typedef enum rexmpp_xml_node_type rexmpp_xml_node_type_t;
+
+struct rexmpp_xml_node {
+  rexmpp_xml_node_type_t type;
+  union {
+    struct {
+      rexmpp_xml_qname_t qname;
+      rexmpp_xml_attr_t *attributes;
+      rexmpp_xml_t *children;
+    } elem;
+    char *text;
+  } alt;
+  rexmpp_xml_t *next;
+};
+
+
+/**
+   @brief Frees a single XML node. Does not free its siblings.
+*/
+void rexmpp_xml_free (rexmpp_xml_t *node);
+
+/**
+   @brief Frees an XML node and its siblings.
+*/
+void rexmpp_xml_free_list (rexmpp_xml_t *node);
+
+/**
+   @brief Clones a single XML node, without its siblings.
+*/
+rexmpp_xml_t *rexmpp_xml_clone (rexmpp_xml_t *node);
+
+/**
+   @brief Clones an XML node, together with its siblings.
+*/
+rexmpp_xml_t *rexmpp_xml_clone_list (rexmpp_xml_t *node);
+
+/**
+   @brief Creates a single ::rexmpp_xml_t XML node out of libxml2's
+   xmlNode, without siblings.
+*/
+rexmpp_xml_t *rexmpp_xml_from_libxml2 (xmlNodePtr from);
+
+/**
+   @brief Creates a ::rexmpp_xml_t XML node out of libxml2's xmlNode,
+   with siblings.
+*/
+rexmpp_xml_t *rexmpp_xml_from_libxml2_list (xmlNodePtr from);
+
+xmlNodePtr rexmpp_xml_to_libxml2 (rexmpp_xml_t *from);
+
+xmlNodePtr rexmpp_xml_to_libxml2_list (rexmpp_xml_t *from);
+
+/**
+   @brief Creates a textual ::rexmpp_xml_t XML node (with type =
+   ::REXMPP_XML_TEXT).
+*/
+rexmpp_xml_t *rexmpp_xml_new_text (const char *str);
+
+/**
+   @brief Creates an element ::rexmpp_xml_t XML node (with type =
+   ::REXMPP_XML_ELEMENT).
+*/
+rexmpp_xml_t *rexmpp_xml_new_elem (const char *name,
+                                   const char *namespace);
+
+/**
+   @brief Adds a child node.
+*/
+void rexmpp_xml_add_child (rexmpp_xml_t *node,
+                           rexmpp_xml_t *child);
+
+/**
+   @brief Creates a text node, and adds it as a child.
+*/
+int rexmpp_xml_add_text (rexmpp_xml_t *node,
+                         const char *str);
+
+rexmpp_xml_attr_t *rexmpp_xml_attr_new (const char *name,
+                                        const char *namespace,
+                                        const char *value);
+
+int rexmpp_xml_add_attr (rexmpp_xml_t *node,
+                         const char *name,
+                         const char *value);
+
+int rexmpp_xml_remove_attr_ns (rexmpp_xml_t *node,
+                               const char *name,
+                               const char *namespace);
+
+int rexmpp_xml_remove_attr (rexmpp_xml_t *node,
+                            const char *name);
+
+int rexmpp_xml_add_attr_ns (rexmpp_xml_t *node,
+                            const char *name,
+                            const char *namespace,
+                            const char *value);
+
+/**
+   @brief Adds an "id" attribute to an XML stanza.
+   @param[in,out] s ::rexmpp
+   @param[in] node A pointer to an XML stanza.
+   @returns The same pointer as on input, for more convenient
+   composition.
+*/
+rexmpp_xml_t *
+rexmpp_xml_add_id (rexmpp_t *s,
+                   rexmpp_xml_t *node);
+
+/**
+   @brief A helper function for XML serialisation.
+   @param[in] node An XML node.
+   @returns A string (must be freed by the caller).
+*/
+char *rexmpp_xml_serialize (rexmpp_xml_t *node);
+
+/**
+   @brief Count the number of siblings after a given node.
+*/
+unsigned int rexmpp_xml_siblings_count (rexmpp_xml_t *node);
+
+/**
+   @brief Compares the node's name and namespace to given ones.
+*/
+int rexmpp_xml_match (rexmpp_xml_t *node,
+                      const char *namespace,
+                      const char *name);
+
+int rexmpp_xml_is_stanza (rexmpp_xml_t *node);
+
+/**
+   @brief Compose an 'error' element.
+*/
+rexmpp_xml_t *rexmpp_xml_error (const char *type, const char *condition);
+
+/**
+   @brief Matches an XML node against a namespace and an element name.
+   @param[in] node An XML node to match.
+   @param[in] namespace An XML namespace. Can be NULL (matches
+   anything), and it is assumed that the default namespace is
+   "jabber:client" (so if it is "jabber:client" and an element doesn't
+   have a namespace defined, this function counts that as a match).
+   @param[in] name Element name. Can be NULL (matches anything).
+   @returns 1 on a successful match, 0 otherwise.
+*/
+int rexmpp_xml_attr_match (rexmpp_xml_attr_t *attr,
+                           const char *namespace,
+                           const char *name);
+
+rexmpp_xml_attr_t *rexmpp_xml_find_attr (rexmpp_xml_t *node,
+                                         const char *name,
+                                         const char *namespace);
+
+const char *rexmpp_xml_find_attr_val_ns (rexmpp_xml_t *node,
+                                         const char *name,
+                                         const char *namespace);
+
+const char *rexmpp_xml_find_attr_val (rexmpp_xml_t *node,
+                                      const char *name);
+
+/**
+   @brief Finds a child element of an XML node, which matches the
+   given namespace and name.
+   @param[in] node The node containing child nodes.
+   @param[in] namespace The namespace to look for.
+   @param[in] name The element name to look for.
+   @returns A pointer to the first matching child node, or NULL if no
+   matching child elements found.
+*/
+rexmpp_xml_t *rexmpp_xml_find_child (rexmpp_xml_t *node,
+                                     const char *namespace,
+                                     const char *name);
+
+rexmpp_xml_t *rexmpp_xml_children (rexmpp_xml_t *node);
+
+const char *rexmpp_xml_text (rexmpp_xml_t *node);
+
+const char *rexmpp_xml_text_child (rexmpp_xml_t *node);
+
+rexmpp_xml_t *rexmpp_xml_first_elem_child (rexmpp_xml_t *node);
+
+rexmpp_xml_t *rexmpp_xml_next_elem_sibling (rexmpp_xml_t *node);
+
+/**
+   @brief Compares two XML elements.
+*/
+int rexmpp_xml_eq (rexmpp_xml_t *n1, rexmpp_xml_t *n2);
+
+/**
+   @brief A helper function for XML parsing.
+   @param[in] str A string to parse.
+   @param[in] str_len String length.
+   @returns Parsed XML, or NULL on failure.
+*/
+rexmpp_xml_t *rexmpp_xml_parse (const char *str, int str_len);
+
+rexmpp_xml_t *rexmpp_xml_read_file (const char *path);
+int rexmpp_xml_write_file (const char *path, rexmpp_xml_t* node);
+
+#endif