From f249ba1f7198e491c8e0b794a748095cdd1278a7 Mon Sep 17 00:00:00 2001
From: Eric Biggers <ebiggers3@gmail.com>
Date: Sat, 19 Dec 2015 16:32:22 -0600
Subject: [PATCH] xml.c: support numerically indexed elements in
 wimlib_{get,set}_image_property()

---
 include/wimlib.h | 16 ++++++++++++++--
 src/xml.c        | 44 ++++++++++++++++++++++++++++++++++++++++----
 2 files changed, 54 insertions(+), 6 deletions(-)

diff --git a/include/wimlib.h b/include/wimlib.h
index 09462278..10f9bb7e 100644
--- a/include/wimlib.h
+++ b/include/wimlib.h
@@ -3186,7 +3186,11 @@ wimlib_get_image_name(const WIMStruct *wim, int image);
  *	"TOTALBYTES".  The name can contain forward slashes to indicate a nested
  *	XML element; for example, "WINDOWS/VERSION/BUILD" indicates the BUILD
  *	element nested within the VERSION element nested within the WINDOWS
- *	element.  The <tt>[</tt> character is reserved for future use.
+ *	element.  Since wimlib v1.8.4, a bracketed number can be used to
+ *	indicate one of several identically-named elements; for example,
+ *	"WINDOWS/LANGUAGES/LANGUAGE[2]" indicates the second "LANGUAGE" element
+ *	nested within the "WINDOWS/LANGUAGES" element.  Note that element names
+ *	are case sensitive.
  *
  * @return
  *	The property's value as a ::wimlib_tchar string, or @c NULL if there is
@@ -4043,6 +4047,13 @@ wimlib_set_image_name(WIMStruct *wim, int image, const wimlib_tchar *name);
  * @param property_name
  *	The name of the image property in the same format documented for
  *	wimlib_get_image_property().
+ *	<br/>
+ *	Note: if creating a new element using a bracketed index such as
+ *	"WINDOWS/LANGUAGES/LANGUAGE[2]", the highest index that can be specified
+ *	is one greater than the number of existing elements with that same name,
+ *	excluding the index.  That means that if you are adding a list of new
+ *	elements, they must be added sequentially from the first index (1) to
+ *	the last index (n).
  * @param property_value
  *	If not NULL and not empty, the property is set to this value.
  *	Otherwise, the property is removed from the XML document.
@@ -4052,7 +4063,8 @@ wimlib_set_image_name(WIMStruct *wim, int image, const wimlib_tchar *name);
  * @retval ::WIMLIB_ERR_INVALID_IMAGE
  *	@p image does not exist in @p wim.
  * @retval ::WIMLIB_ERR_INVALID_PARAM
- *	@p property_name has an unsupported format.
+ *	@p property_name has an unsupported format, or @p property_name included
+ *	a bracketed index that was too high.
  */
 extern int
 wimlib_set_image_property(WIMStruct *wim, int image,
diff --git a/src/xml.c b/src/xml.c
index 8280e8ed..d4647065 100644
--- a/src/xml.c
+++ b/src/xml.c
@@ -342,6 +342,32 @@ alloc_wim_xml_info(void)
 	return info;
 }
 
+static bool
+parse_index(xmlChar **pp, uint32_t *index_ret)
+{
+	xmlChar *p = *pp;
+	uint32_t index = 0;
+
+	*p++ = '\0'; /* overwrite '[' */
+	while (*p >= '0' && *p <= '9') {
+		uint32_t n = (index * 10) + (*p++ - '0');
+		if (n < index)
+			return false;
+		index = n;
+	}
+	if (index == 0)
+		return false;
+	if (*p != ']')
+		return false;
+	p++;
+	if (*p != '/' && *p != '\0')
+		return false;
+
+	*pp = p;
+	*index_ret = index;
+	return true;
+}
+
 static int
 do_xml_path_walk(xmlNode *node, const xmlChar *path, bool create,
 		 xmlNode **result_ret)
@@ -362,34 +388,44 @@ do_xml_path_walk(xmlNode *node, const xmlChar *path, bool create,
 
 	if (*p == '/')
 		goto bad_syntax;
-	if (strchr(p, '[')) /* reserved for future use */
-		goto bad_syntax;
 	c = *p;
 
 	while (c != '\0') {
 		const xmlChar *name;
 		xmlNode *child;
+		uint32_t index = 1;
 
 		/* We have another path component.  */
 
 		/* Parse the element name.  */
 		name = p;
-		while (*p != '/' && *p != '\0')
+		while (*p != '/' && *p != '\0' && *p != '[')
 			p++;
 		if (p == name) /* empty name?  */
 			goto bad_syntax;
+
+		/* Handle a bracketed index, if one was specified.  */
+		if (*p == '[' && !parse_index(&p, &index))
+			goto bad_syntax;
+
 		c = *p;
 		*p = '\0';
 
 		/* Look for a matching child.  */
 		node_for_each_child(node, child)
-			if (node_is_element(child, name))
+			if (node_is_element(child, name) && !--index)
 				goto next_step;
 
 		/* No child matched the path.  If create=false, the lookup
 		 * failed.  If create=true, create the needed element.  */
 		if (!create)
 			return 0;
+
+		/* We can't create an element at index 'n' if indices 1...n-1
+		 * didn't already exist.  */
+		if (index != 1)
+			return WIMLIB_ERR_INVALID_PARAM;
+
 		child = xmlNewChild(node, NULL, name, NULL);
 		if (!child)
 			return WIMLIB_ERR_NOMEM;
-- 
2.43.0