Better progdocs for filters

1 files changed, 10 insertions, 0 deletions

diff --git a/filter/filter.c b/filter/filter.c
index b4e0105..540ce13 100644
--- a/filter/filter.c
+++ b/filter/filter.c
@@ -260,6 +260,16 @@ rta_cow(void)
  *
  * Interpret given tree of filter instructions. This is core function
  * of filter system and does all the hard work.
+ *
+ * Each instruction has 4 fields: code (which is instruction code),
+ * aux (which is extension to instruction code, typically type),
+ * arg1 and arg2 - arguments. Depending on instruction, arguments
+ * are either integers, or pointers to instruction trees. Common 
+ * instructions like +, that have two expressions as arguments use
+ * TWOARGS macro to get both of them evaluated.
+ *
+ * &f_val structures are copied around, so there are no problems with
+ * memory managment.
  */
 static struct f_val
 interpret(struct f_inst *what)