Add support for iterating over tag data container

- rpmtd iterator init + next methods
- string accessor method for RPM_STRING_TYPE and RPM_STRING_ARRAY_TYPE

lib/rpmtd.c

@@ -52,3 +52,42 @@ rpmTag rpmtdTag(rpmtd td)
     return td->tag;
 }
 
+int rpmtdInit(rpmtd td)
+{
+    assert(td != NULL);
+
+    /* XXX check that this is an array type? */
+    td->ix = -1;
+    return 0;
+}
+
+int rpmtdNext(rpmtd td)
+{
+    int i = -1;
+
+    assert(td != NULL);
+    if (++td->ix >= 0) {
+	if (td->ix < td->count) {
+	    i = td->ix;
+	} else {
+	    td->ix = i;
+	}
+    }
+    return i;
+}
+
+const char * rpmtdGetString(rpmtd td)
+{
+    const char *str = NULL;
+
+    assert(td != NULL);
+
+    if (td->type == RPM_STRING_TYPE) {
+	str = (const char *) td->data;
+    } else if (td->type == RPM_STRING_ARRAY_TYPE) {
+	/* XXX TODO: check for array bounds */
+	int ix = (td->ix >= 0 ? td->ix : 0);
+	str = *((const char**) td->data + ix);
+    } 
+    return str;
+}

lib/rpmtd.h

@@ -56,4 +56,28 @@ rpm_count_t rpmtdCount(rpmtd td);
  */
 rpmTag rpmtdTag(rpmtd td);
 
+/** \ingroup rpmtd
+ * Initialize tag container for iteration
+ * @param td		Tag data container
+ * @return		0 on success
+ */
+int rpmtdInit(rpmtd td);
+
+/** \ingroup rpmtd
+ * Iterate over tag data container.
+ * @param td		Tag data container
+ * @return		Tag data container iterator index, -1 on termination
+ */
+int rpmtdNext(rpmtd td);
+
+/** \ingroup rpmtd
+ * Return string data from tag container.
+ * For string types, just return the string. On string array types,
+ * return the string from current iteration index. If the tag container
+ * is not for a string type, NULL is returned.
+ * @param td		Tag data container
+ * @return		String constant from container, NULL on error
+ */
+const char * rpmtdGetString(rpmtd td);
+
 #endif /* _RPMTD_H */