From 45c5dcc531fbc80d1e62e2e845723d423e5660b3 Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Wed, 17 Apr 2024 18:46:01 +0200 Subject: Adding upstream version 0.16.1. Signed-off-by: Daniel Baumann --- doc/tevent_data.dox | 137 ++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 137 insertions(+) create mode 100644 doc/tevent_data.dox (limited to 'doc/tevent_data.dox') diff --git a/doc/tevent_data.dox b/doc/tevent_data.dox new file mode 100644 index 0000000..dbe7a04 --- /dev/null +++ b/doc/tevent_data.dox @@ -0,0 +1,137 @@ +/** +@page tevent_data Chapter 3: Accessing data +@section data Accessing data with tevent + +A tevent request is (usually) created together with a structure for storing the +data necessary for an asynchronous computation. For these private data, tevent +library uses void (generic) pointers, therefore any data type can be very +simply pointed at. However, this attitude requires clear and guaranteed +knowledge of the data type that will be handled, in advance. Private data can +be of 2 types: connected with a request itself or given as an individual +argument to a callback. It is necessary to differentiate these types, because +there is a slightly different method of data access for each. There are two +possibilities how to access data that is given as an argument directly to a +callback. The difference lies in the pointer that is returned. In one case it +is the data type specified in the function’s argument, in another void* is +returned. + +@code +void tevent_req_callback_data (struct tevent_req *req, #type) +void tevent_req_callback_data_void (struct tevent_req *req) +@endcode + + +To obtain data that are strictly bound to a request, this function is the only +direct procedure. + +@code +void *tevent_req_data (struct tevent_req *req, #type) +@endcode + +Example with both calls which differs between private data within tevent +request and data handed over as an argument. + +@code +#include +#include +#include + +struct foo_state { + int x; +}; + +struct testA { + int y; +}; + + +static void foo_done(struct tevent_req *req) { + // a->x contains 10 since it came from foo_send + struct foo_state *a = tevent_req_data(req, struct foo_state); + + // b->y contains 9 since it came from run + struct testA *b = tevent_req_callback_data(req, struct testA); + + // c->y contains 9 since it came from run we just used a different way + // of getting it. + struct testA *c = (struct testA *)tevent_req_callback_data_void(req); + + printf("a->x: %d\n", a->x); + printf("b->y: %d\n", b->y); + printf("c->y: %d\n", c->y); +} + + +struct tevent_req * foo_send(TALLOC_CTX *mem_ctx, struct tevent_context *event_ctx) { + +printf("_send\n"); +struct tevent_req *req; +struct foo_state *state; + +req = tevent_req_create(event_ctx, &state, struct foo_state); +state->x = 10; + +return req; +} + +static void run(struct tevent_context *ev, struct tevent_timer *te, + struct timeval current_time, void *private_data) { + struct tevent_req *req; + struct testA *tmp = talloc(ev, struct testA); + + // Note that we did not use the private data passed in + + tmp->y = 9; + req = foo_send(ev, ev); + + tevent_req_set_callback(req, foo_done, tmp); + tevent_req_done(req); + +} + +int main (int argc, char **argv) { + + struct tevent_context *event_ctx; + struct testA *data; + TALLOC_CTX *mem_ctx; + struct tevent_timer *time_event; + + mem_ctx = talloc_new(NULL); //parent + if (mem_ctx == NULL) + return EXIT_FAILURE; + + event_ctx = tevent_context_init(mem_ctx); + if (event_ctx == NULL) + return EXIT_FAILURE; + + data = talloc(mem_ctx, struct testA); + data->y = 11; + + time_event = tevent_add_timer(event_ctx, + mem_ctx, + tevent_timeval_current(), + run, + data); + if (time_event == NULL) { + fprintf(stderr, " FAILED\n"); + return EXIT_FAILURE; + } + + tevent_loop_once(event_ctx); + + talloc_free(mem_ctx); + + printf("Quit\n"); + return EXIT_SUCCESS; +} +@endcode + +Output of this example is: + +@code +a->x: 10 +b->y: 9 +c->y: 9 +@endcode + +*/ -- cgit v1.2.3