+=head1 C API
+
+=head2 C<sub_op_config_t>
+
+A typedef'd struct that configures how L<Sub::Op> should handle a given subroutine name.
+It has the following members :
+
+=over 4
+
+=item *
+
+C<const char *name>
+
+The name of the subroutine you want to replace.
+Allowed to be static.
+
+=item *
+
+C<STRLEN namelen>
+
+C<name>'s length, in bytes.
+
+=item *
+
+C<Perl_ppaddr_t pp>
+
+The pp function that will be called instead of the subroutine.
+C<Perl_ppaddr_t> is a typedef'd function pointer defined by perl as :
+
+ typedef OP *(*Perl_ppaddr_t)(pTHX);
+
+=item *
+
+C<sub_op_check_t check>
+
+An optional callback that will be called each time a call to C<name> is replaced.
+You can use it to attach extra info to those ops (e.g. with a pointer table) or to perform more optimizations to the optree.
+C<sub_op_check_t> is a typedef'd function pointer defined by :
+
+ typedef OP *(*sub_op_check_t)(pTHX_ OP *, void *);
+
+=item *
+
+C<void *ud>
+
+An optional user data passed to the C<check> callback.
+
+=back
+
+=head2 C<void sub_op_register(pTHX_ const sub_op_config_t *c)>
+
+Registers a name and its configuration into L<Sub::Op>.
+The caller is responsible for allocating and freeing the C<sub_op_config_t> object.
+No pointer to it or to its members is kept.
+
+=head1 PERL API
+
+=head2 C<enable $name, [ $pkg ]>
+
+Enable the replacement with a custom opcode of calls to the C<$name> subroutine of the C<$pkg> package in the current lexical scope.
+A pp callback must have been registered for C<$name> by calling the C function C<sub_op_register> in the XS section of your module.
+
+When C<$pkg> is not set, it defaults to the caller package.
+
+=cut
+