xmlapi: Working with attributes: xml_set and xml

Working with attributes: xml_set and xml_attrval

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Setting an attribute is a little complicated. If the attribute is already represented in the element's attribute list, then we free the old value, allocate space for a copy of the new value, and copy it. Otherwise we allocate a new attribute holder and copy both name and value into it.

This function comes in three varieties for your viewing pleasure: xml_set just uses strdup to make a copy of the value you give it, xml_setf treats its second parameter as a printf-style format and builds the value, and xml_setnum takes an integer and formats it into a string. As you can imagine, I did xml_setnum before I even thought of xml_setf.

Oh -- another variant. The xml_set_nodup function can be used to take over management of a malloc'd string buffer. It works exactly the same as xml_set except that the string is not duplicated. Useful for when you save locations obtained from xml_getlocbuf, for instance.

July 18, 2001: Yet another variant: xml_attrcat tacks strings onto the end of already-set attribute values. It uses valsize to grow the allocated buffer accordingly. This is support for a better version of wftk_value_interpret, by the way.

XMLAPI void xml_set (XML * xml, const char * name, const char * value)
{
   ATTR * attr;

   attr = xml->attrs;
   while (attr) {
      if (!strcmp (attr->name, name)) break;
      attr = attr->next;
   }

   if (attr) {
      FREE ((void *) (attr->value));
      attr->value = strdup (value);
      attr->valsize = strlen (value) + 1;
      return;
   }

   if (xml->attrs == NULL) {
      attr = (ATTR *) MALLOC (sizeof (struct _attr));
      xml->attrs = attr;
   } else {
      attr = xml->attrs;
      while (attr->next) attr = attr->next;
      attr->next = (ATTR *) MALLOC (sizeof (struct _attr));
      attr = attr->next;
   }

   attr->next = NULL;
   attr->name = strdup (name);
   attr->value = strdup (value);
   attr->valsize = strlen (value + 1);
}
XMLAPI void xml_setf (XML * xml, const char *name, const char *format, ...)
{
   ATTR * attr;
   va_list args;
   char * value;

   va_start (args, format);
   value = _xml_string_format (format, args);
   va_end (args);

   attr = xml->attrs;
   while (attr) {
      if (!strcmp (attr->name, name)) break;
      attr = attr->next;
   }

   if (attr) {
      FREE ((void *) (attr->value));
      attr->value = value;
      attr->valsize = 0;
      return;
   }

   if (xml->attrs == NULL) {
      attr = (ATTR *) MALLOC (sizeof (struct _attr));
      xml->attrs = attr;
   } else {
      attr = xml->attrs;
      while (attr->next) attr = attr->next;
      attr->next = (ATTR *) MALLOC (sizeof (struct _attr));
      attr = attr->next;
   }

   attr->next = NULL;
   attr->name = strdup (name);
   attr->value = value;
   attr->valsize = 0;
}
XMLAPI void xml_setnum (XML * xml, const char *attr, int number)
{
   char buf[sizeof(number) * 3 + 1];
   sprintf (buf, "%d", number);
   xml_set (xml, attr, buf);
}
XMLAPI void xml_set_nodup (XML * xml, const char * name, char * value)
{
   ATTR * attr;

   attr = xml->attrs;
   while (attr) {
      if (!strcmp (attr->name, name)) break;
      attr = attr->next;
   }

   if (attr) {
      FREE ((void *) (attr->value));
      attr->value = value;
      attr->valsize = 0;
      return;
   }

   if (xml->attrs == NULL) {
      attr = (ATTR *) MALLOC (sizeof (struct _attr));
      xml->attrs = attr;
   } else {
      attr = xml->attrs;
      while (attr->next) attr = attr->next;
      attr->next = (ATTR *) MALLOC (sizeof (struct _attr));
      attr = attr->next;
   }

   attr->next = NULL;
   attr->name = strdup (name);
   attr->value = value;
   attr->valsize = 0;
}
XMLAPI void xml_attrcat (XML * xml, const char * name, const char * value)
{
   ATTR * attr;
   int len;

   attr = xml->attrs;
   while (attr) {
      if (!strcmp (attr->name, name)) break;
      attr = attr->next;
   }

   if (!attr) xml_set (xml, name, value);
   else {
      len = strlen (attr->value) + strlen (value) + 1;
      if (len > attr->valsize) {
         while (attr->valsize < len) attr->valsize += 256;
         attr->value = (char *) REALLOC (attr->value, attr->valsize);
      }
      strcat (attr->value, value);
   }
}
XMLAPI void xml_attrncat (XML * xml, const char * name, const char * value, int length)
{
   ATTR * attr;
   int len;

   attr = xml->attrs;
   while (attr) {
      if (!strcmp (attr->name, name)) break;
      attr = attr->next;
   }

   if (!attr) {
      xml_set (xml, name, "");
      attr = xml->attrs;
      while (attr) {
         if (!strcmp (attr->name, name)) break;
         attr = attr->next;
      }
   }
   if (!attr) return; /* This is probably a dumb way to handle low-mem situations, but... */

   len = strlen (attr->value) + length + 1;
   if (len > attr->valsize) {
      while (attr->valsize < len) attr->valsize += 256;
      attr->value = (char *) REALLOC (attr->value, attr->valsize);
   }
   strncat (attr->value, value, length);
}

Retrieving a value, on the other hand, is rather simple. So simple, in fact, that we only have two different ways to do it (instead of six or more).

XMLAPI const char * xml_attrval (XML * element,const char * name)
{
   ATTR * attr;

   attr = element->attrs;
   while (attr) {
      if (!strcmp (attr->name, name)) return (attr->value);
      attr = attr->next;
   }
   return ("");
}
XMLAPI int xml_attrvalnum (XML * element, const char * name)
{
   return (atoi (xml_attrval (element, name)));
}

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This code and documentation are released under the terms of the GNU license. They are additionally copyright (c) 2000, Vivtek. All rights reserved except those explicitly granted under the terms of the GNU license. This presentation was created using LPML.