diff options
Diffstat (limited to 'erts/doc/src/erl_nif.xml')
| -rw-r--r-- | erts/doc/src/erl_nif.xml | 63 |
1 files changed, 59 insertions, 4 deletions
diff --git a/erts/doc/src/erl_nif.xml b/erts/doc/src/erl_nif.xml index 5cbeddabd9..34042cb4de 100644 --- a/erts/doc/src/erl_nif.xml +++ b/erts/doc/src/erl_nif.xml @@ -3056,12 +3056,18 @@ enif_map_iterator_destroy(env, &iter);</code> <p>Argument <c>mode</c> describes the type of events to wait for. It can be <c>ERL_NIF_SELECT_READ</c>, <c>ERL_NIF_SELECT_WRITE</c> or a bitwise OR combination to wait for both. It can also be <c>ERL_NIF_SELECT_STOP</c> - which is described further below. When a read or write event is triggered, + or <c>ERL_NIF_SELECT_CANCEL</c> which are described further + below. When a read or write event is triggered, a notification message like this is sent to the process identified by <c>pid</c>:</p> <code type="none">{select, Obj, Ref, ready_input | ready_output}</code> <p><c>ready_input</c> or <c>ready_output</c> indicates if the event object is ready for reading or writing.</p> + <note><p>For complete control over the message format use the newer functions + <seealso marker="#enif_select_read"><c>enif_select_read</c></seealso> or + <seealso marker="#enif_select_write"><c>enif_select_write</c></seealso> + introduced in erts-11.0 (OTP-22.0).</p> + </note> <p>Argument <c>pid</c> may be <c>NULL</c> to indicate the calling process.</p> <p>Argument <c>obj</c> is a resource object obtained from <seealso marker="#enif_alloc_resource"><c>enif_alloc_resource</c></seealso>. @@ -3077,13 +3083,21 @@ enif_map_iterator_destroy(env, &iter);</code> <p>The notifications are one-shot only. To receive further notifications of the same type (read or write), repeated calls to <c>enif_select</c> must be made after receiving each notification.</p> + <p><c>ERL_NIF_SELECT_CANCEL</c> can be used to cancel previously + selected events. It must be used in a bitwise OR combination with + <c>ERL_NIF_SELECT_READ</c> and/or <c>ERL_NIF_SELECT_WRITE</c> to + indicate which type of event to cancel. The return value will + tell if the event was actualy cancelled or if a notification may + already have been sent.</p> <p>Use <c>ERL_NIF_SELECT_STOP</c> as <c>mode</c> in order to safely close an event object that has been passed to <c>enif_select</c>. The <seealso marker="#ErlNifResourceStop"><c>stop</c></seealso> callback of the resource <c>obj</c> will be called when it is safe to close the event object. This safe way of closing event objects must be used - even if all notifications have been received and no further calls to - <c>enif_select</c> have been made.</p> + even if all notifications have been received (or cancelled) and no + further calls to <c>enif_select</c> have been made. + <c>ERL_NIF_SELECT_STOP</c> will first cancel any selected events + before it calls or schedules the <c>stop</c> callback.</p> <p>The first call to <c>enif_select</c> for a specific OS <c>event</c> will establish a relation between the event object and the containing resource. All subsequent calls for an <c>event</c> must pass its containing resource as argument @@ -3105,7 +3119,15 @@ enif_map_iterator_destroy(env, &iter);</code> <item>The stop callback was called directly by <c>enif_select</c>.</item> <tag><c>ERL_NIF_SELECT_STOP_SCHEDULED</c></tag> <item>The stop callback was scheduled to run on some other thread - or later by this thread.</item> + or later by this thread.</item> + <tag><c>ERL_NIF_SELECT_READ_CANCELLED</c></tag> + <item>A read event was cancelled by <c>ERL_NIF_SELECT_CANCEL</c> or + <c>ERL_NIF_SELECT_STOP</c> and is guaranteed not to generate a + <c>ready_input</c> notification message.</item> + <tag><c>ERL_NIF_SELECT_WRITE_CANCELLED</c></tag> + <item>A write event was cancelled by <c>ERL_NIF_SELECT_CANCEL</c> or + <c>ERL_NIF_SELECT_STOP</c> and is guaranteed not to generate a + <c>ready_output</c> notification message.</item> </taglist> <p>Returns a negative value if the call failed where the following bits can be set:</p> <taglist> @@ -3131,6 +3153,39 @@ if (retval & ERL_NIF_SELECT_STOP_CALLED) { } </code> </note> + <note><p>The mode flag <c>ERL_NIF_SELECT_CANCEL</c> and the return flags + <c>ERL_NIF_SELECT_READ_CANCELLED</c> and + <c>ERL_NIF_SELECT_WRITE_CANCELLED</c> were introduced in erts-11.0 + (OTP-22.0).</p> + </note> + </desc> + </func> + + <func> + <name since="OTP 22.0"><ret>int</ret> + <nametext>enif_select_read(ErlNifEnv* env, ErlNifEvent event, void* obj, + const ErlNifPid* pid, ERL_NIF_TERM msg, ErlNifEnv* msg_env)</nametext> + </name> + <name since="OTP 22.0"><ret>int</ret> + <nametext>enif_select_write(ErlNifEnv* env, ErlNifEvent event, void* obj, + const ErlNifPid* pid, ERL_NIF_TERM msg, ErlNifEnv* msg_env)</nametext> + </name> + <fsummary>Manage subscription on IO event.</fsummary> + <desc> + <p>These are variants of <seealso marker="#enif_select">enif_select</seealso> + where you can supply your own message term <c>msg</c> that will be sent to + the process instead of the predefined tuple <c>{select,_,_,_}.</c></p> + <p>Argument <c>msg_env</c> must either be <c>NULL</c> or the environment of + <c>msg</c> allocated with <seealso marker="#enif_alloc_env"> + <c>enif_alloc_env</c></seealso>. If argument <c>msg_env</c> is + <c>NULL</c> the term <c>msg</c> will be copied, otherwise both + <c>msg</c> and <c>msg_env</c> will be invalidated by a successful call + to <c>enif_select_read</c> or <c>enif_select_write</c>.</p> + <p>Apart from the message format <c>enif_select_read</c> and + <c>enif_select_write</c> behaves exactly the same as <seealso + marker="#enif_select">enif_select</seealso> with argument <c>mode</c> as + either <c>ERL_NIF_SELECT_READ</c> or <c>ERL_NIF_SELECT_WRITE</c>. To + cancel or close events use <seealso marker="#enif_select">enif_select</seealso>.</p> </desc> </func> |