-the data item as parameters.
-This function can be quite useful when used as follows:
- void cleanup(STUFF *a)
- { STUFF_free(a); }
- lh_doall(hash,(LHASH_DOALL_FN_TYPE)cleanup);
- lh_free(hash);
-This can be used to free all the entries. lh_free() then cleans up the
-'buckets' that point to nothing. When doing this, be careful if you
-delete entries from the hash table in B<func>: the table may decrease
-in size, moving item that you are currently on down lower in the hash
-table. This could cause some entries to be skipped. The best
-solution to this problem is to set hash-E<gt>down_load=0 before you
-start. This will stop the hash table ever being decreased in size.
-
-lh_doall_arg() is the same as lh_doall() except that B<func> will
-be called with B<arg> as the second argument and B<func> should be
-of type B<LHASH_DOALL_ARG_FN_TYPE> (a callback prototype that is
-passed an extra argument).
-
+the data item as its parameter. For lh_doall() and lh_doall_arg(),
+function pointer casting should be avoided in the callbacks (see
+B<NOTE>) - instead, either declare the callbacks to match the
+prototype required in lh_new() or use the decare/implement macros to
+create type-safe wrappers that cast variables prior to calling your
+type-specific callbacks. An example of this is illustrated here where
+the callback is used to cleanup resources for items in the hash table
+prior to the hashtable itself being deallocated:
+
+ /* Cleans up resources belonging to 'a' (this is implemented elsewhere) */
+ void STUFF_cleanup(STUFF *a);
+ /* Implement a prototype-compatible wrapper for "STUFF_cleanup" */
+ IMPLEMENT_LHASH_DOALL_FN(STUFF_cleanup, STUFF *)
+ /* ... then later in the code ... */
+ /* So to run "STUFF_cleanup" against all items in a hash table ... */
+ lh_doall(hashtable, LHASH_DOALL_FN(STUFF_cleanup));
+ /* Then the hash table itself can be deallocated */
+ lh_free(hashtable);
+
+When doing this, be careful if you delete entries from the hash table
+in your callbacks: the table may decrease in size, moving the item
+that you are currently on down lower in the hash table - this could
+cause some entries to be skipped during the iteration. The second
+best solution to this problem is to set hash-E<gt>down_load=0 before
+you start (which will stop the hash table ever decreasing in size).
+The best solution is probably to avoid deleting items from the hash
+table inside a "doall" callback!
+
+lh_doall_arg() is the same as lh_doall() except that B<func> will be
+called with B<arg> as the second argument and B<func> should be of
+type B<LHASH_DOALL_ARG_FN_TYPE> (a callback prototype that is passed
+both the table entry and an extra argument). As with lh_doall(), you
+can instead choose to declare your callback with a prototype matching
+the types you are dealing with and use the declare/implement macros to
+create compatible wrappers that cast variables before calling your
+type-specific callbacks. An example of this is demonstrated here
+(printing all hash table entries to a BIO that is provided by the
+caller):
+
+ /* Prints item 'a' to 'output_bio' (this is implemented elsewhere) */
+ void STUFF_print(const STUFF *a, BIO *output_bio);
+ /* Implement a prototype-compatible wrapper for "STUFF_print" */
+ static IMPLEMENT_LHASH_DOALL_ARG_FN(STUFF_print, const STUFF *, BIO *)
+ /* ... then later in the code ... */
+ /* Print out the entire hashtable to a particular BIO */
+ lh_doall_arg(hashtable, LHASH_DOALL_ARG_FN(STUFF_print), logging_bio);
+