Add safe macros for switching over sbuffs

diff --git a/src/lib/util/sbuff.h b/src/lib/util/sbuff.h
index 77c5bbc3faebe853de3155c04ea9e47a0e5d548a..79aa855899da2135cecc4e85cbd4150ce4494c17 100644 (file)
--- a/src/lib/util/sbuff.h
+++ b/src/lib/util/sbuff.h
@@ -788,6 +788,9 @@ static inline fr_sbuff_t *fr_sbuff_init_talloc(TALLOC_CTX *ctx,
        ))
 
 /** Return a pointer to the 'current' position of an sbuff or one of its markers
+ *
+ * @note Should not be derferenced as it may point past the end of the buffer.
+ * Use #fr_sbuff_char to get the current char.
  *
  * @param[in] _sbuff_or_marker to return the current position of.
  * @return A pointer to the current position of the buffer or marker.
@@ -825,6 +828,27 @@ static inline fr_sbuff_t *fr_sbuff_init_talloc(TALLOC_CTX *ctx,
                  fr_sbuff_marker_t *           : ((fr_sbuff_marker_t const *)(_sbuff_or_marker))->parent->shifted, \
                  fr_sbuff_marker_t const *     : ((fr_sbuff_marker_t const *)(_sbuff_or_marker))->parent->shifted \
        ))
+
+/** Return the current char pointed to by the sbuff or '\0' if no more chars remain
+ *
+ * @note Should be used in place of #fr_sbuff_current if switching over the current char.
+ *
+ * @param[in] _sbuff_or_marker to return the current char from.
+ * @param[in] _eob             char used to indicate End of Buffer, usually '\0'.
+ * @return The current char pointed to be the sbuff.
+ */
+#define fr_sbuff_char(_sbuff_or_marker, _eob) \
+       (fr_sbuff_current(_sbuff_or_marker) >= fr_sbuff_end(_sbuff_or_marker) ? _eob : *fr_sbuff_current(_sbuff_or_marker))
+
+/** Start a switch block over the current sbuff char
+ *
+ * @note '\0' is used to indicate EOB.
+ *
+ * @param[in] _sbuff_or_marker to return the current char from.
+ * @param[in] _eob             char used to indicate End of Buffer, usually '\0'.
+ */
+#define fr_sbuff_switch(_sbuff_or_marker, _eob) \
+       switch (fr_sbuff_char(_sbuff_or_marker, _eob))
 /** @} */
 
 /** @name Length calculations