Messages in this thread | | | Date | Fri, 15 Dec 2000 23:48:57 +0100 | From | "J . A . Magallon" <> |
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On 2000/12/15 Werner Almesberger wrote: > LA Walsh wrote: > > Exception: opaque types; there one would have to go via a __ identifier, > i.e. > > <public>/foo.h defines struct __foo ...; > <public>/bar.h includes <public>/foo.h > and uses #define FOOSIZE sizeof(struct __foo) > <private>/foo.h either typedef struct __foo foo_t; > or #define foo __foo /* ugly */ >
Easier: public kernel interfaces only work through pointers. <public>/foo.h typedef struct foo foo_t; foo_t* foo_new(); <private>/foo.h includes <public>/foo.h struct foo { ............... }; and uses #define FOOSIZE sizeof(foo_t)
Drawback: public access is slow (always through foo_set_xxxx_field(foo_t*)) private access from kernel or modules is fast (foo_t->x = ...) Advantage: kernel can change, foo_t internals can change and it is binary compatible. Even public headers can be kernel version independent.
Too kind-of-classroom-not-real-world-useless-thing ? All depends on public access needing full fast paths...
-- Juan Antonio Magallon Lacarta #> cd /pub mailto:jamagallon@able.es #> more beer
Linux werewolf 2.2.19-pre1 #1 SMP Fri Dec 15 22:25:20 CET 2000 i686
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