Re: [Xen-devel] [PATCH 21/28] libxl: ocaml: add wrappers for poll

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Mon, 2013-03-25 at 14:45 +0000, Rob Hoes wrote:
> We need this in order to wrap the event API of libxl.

Other than Dave's comment it looks good to me.

But how does the event model work in your callers today? The intention
with the libxl event interface is that by implementing the right hooks
to register/deregister fds you can just continue to use your existing
event loop (presuming it can take events on fds).

Ian.

> 
> Signed-off-by: Rob Hoes <rob.hoes@xxxxxxxxxx>
> ---
>  tools/ocaml/libs/xl/Makefile     |    2 +-
>  tools/ocaml/libs/xl/poll_stubs.c |  128 
> ++++++++++++++++++++++++++++++++++++++
>  tools/ocaml/libs/xl/poll_stubs.h |    6 ++
>  3 files changed, 135 insertions(+), 1 deletion(-)
>  create mode 100644 tools/ocaml/libs/xl/poll_stubs.c
>  create mode 100644 tools/ocaml/libs/xl/poll_stubs.h
> 
> diff --git a/tools/ocaml/libs/xl/Makefile b/tools/ocaml/libs/xl/Makefile
> index 5a410d2..beca795 100644
> --- a/tools/ocaml/libs/xl/Makefile
> +++ b/tools/ocaml/libs/xl/Makefile
> @@ -15,7 +15,7 @@ OCAMLINCLUDE += -I ../xentoollog
>  LIBS_xenlight = $(LDLIBS_libxenlight)
>  
>  xenlight_OBJS = $(OBJS)
> -xenlight_C_OBJS = xenlight_stubs
> +xenlight_C_OBJS = xenlight_stubs poll_stubs
>  
>  OCAML_LIBRARY = xenlight
>  
> diff --git a/tools/ocaml/libs/xl/poll_stubs.c 
> b/tools/ocaml/libs/xl/poll_stubs.c
> new file mode 100644
> index 0000000..0cf54b9
> --- /dev/null
> +++ b/tools/ocaml/libs/xl/poll_stubs.c
> @@ -0,0 +1,128 @@
> +#include <poll.h>
> +#include <caml/alloc.h>
> +#include <caml/memory.h>
> +#include <caml/signals.h>
> +#include <caml/fail.h>
> +
> +static int list_len(value v)
> +{
> +     int len = 0;
> +     while ( v != Val_emptylist ) {
> +             len++;
> +             v = Field(v, 1);
> +     }
> +     return len;
> +}
> +
> +short Poll_val(value event)
> +{
> +     CAMLparam1(event);
> +     short res = -1;
> +
> +     switch (Int_val(event)) {
> +             case 0: res = POLLIN; break;
> +             case 1: res = POLLPRI; break;
> +             case 2: res = POLLOUT; break;
> +             case 3: res = POLLERR; break;
> +             case 4: res = POLLHUP; break;
> +             case 5: res = POLLNVAL; break;
> +     }
> +
> +     CAMLreturn(res);
> +}
> +
> +short Poll_events_val(value event_list)
> +{
> +     CAMLparam1(event_list);
> +     short events = 0;
> +
> +     while (event_list != Val_emptylist) {
> +             events |= Poll_val(Field(event_list, 0));
> +             event_list = Field(event_list, 1);
> +     }
> +
> +     CAMLreturn(events);
> +}
> +
> +value Val_poll(short event)
> +{
> +     CAMLparam0();
> +     CAMLlocal1(res);
> +
> +     switch (event) {
> +             case POLLIN: res = Val_int(0); break;
> +             case POLLPRI: res = Val_int(1); break;
> +             case POLLOUT: res = Val_int(2); break;
> +             case POLLERR: res = Val_int(3); break;
> +             case POLLHUP: res = Val_int(4); break;
> +             case POLLNVAL: res = Val_int(5); break;
> +     }
> +
> +     CAMLreturn(res);
> +}
> +
> +value add_event(value event_list, short event)
> +{
> +     CAMLparam1(event_list);
> +     CAMLlocal1(new_list);
> +
> +     new_list = caml_alloc(2, 0);
> +     Store_field(new_list, 0, Val_poll(event));
> +     Store_field(new_list, 1, event_list);
> +
> +     CAMLreturn(new_list);
> +}
> +
> +value Val_poll_events(short events)
> +{
> +     CAMLparam0();
> +     CAMLlocal1(event_list);
> +
> +     event_list = Val_emptylist;
> +     if (events & POLLIN)
> +             event_list = add_event(event_list, POLLIN);
> +     if (events & POLLPRI)
> +             event_list = add_event(event_list, POLLPRI);
> +     if (events & POLLOUT)
> +             event_list = add_event(event_list, POLLOUT);
> +     if (events & POLLERR)
> +             event_list = add_event(event_list, POLLERR);
> +     if (events & POLLHUP)
> +             event_list = add_event(event_list, POLLHUP);
> +     if (events & POLLNVAL)
> +             event_list = add_event(event_list, POLLNVAL);
> +
> +     CAMLreturn(event_list);
> +}
> +
> +value stub_poll(value fds)
> +{
> +     CAMLparam1(fds);
> +     CAMLlocal2(fd, tmp);
> +     int rc, i;
> +     const int c_nfds = list_len(fds);
> +     struct pollfd c_fds[c_nfds];
> +
> +     for (i = 0; fds != Val_emptylist; i++) {
> +             fd = Field(fds, 0);
> +             c_fds[i].fd = Int_val(Field(fd, 0));
> +             c_fds[i].events = Poll_events_val(Field(fd, 1));
> +             fds = Field(fds, 1);
> +     }
> +
> +     caml_enter_blocking_section();
> +     rc = poll(c_fds, c_nfds, -1);
> +     caml_leave_blocking_section();
> +
> +     if (rc > 0) {
> +             for (i = c_nfds - 1; i >= 0; i--) {
> +                     tmp = caml_alloc(2, 0);
> +                     Store_field(tmp, 0, Val_poll_events(c_fds[i].revents));
> +                     Store_field(tmp, 1, fds);
> +                     fds = tmp;
> +             }
> +     }
> +
> +     CAMLreturn(fds);
> +}
> +
> diff --git a/tools/ocaml/libs/xl/poll_stubs.h 
> b/tools/ocaml/libs/xl/poll_stubs.h
> new file mode 100644
> index 0000000..0b2332d
> --- /dev/null
> +++ b/tools/ocaml/libs/xl/poll_stubs.h
> @@ -0,0 +1,6 @@
> +#include <caml/alloc.h>
> +
> +short Poll_events_val(value event_list);
> +value Val_poll_events(short events);
> +value stub_poll(value fds);
> +



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