examples/reference/c/eina/src/eina_future.c

#define EFL_EO_API_SUPPORT 1
#define EFL_BETA_API_SUPPORT 1

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>

#include <Eina.h>
#include <Efl_Core.h>

/*
 * A collection of Eina Future examples.
 * TEST 1: Set up a promised future and resolve it from a timer callback.
 * TEST 2: Set up a promised future and reject it from a timer callback.
 * TEST 3: Set up a promised future and then cancel it.
 * TEST 4: Set up a chain of futures that get called one after the other when
 *         the promise is resolved, passing a value among them.
 */

static void _test1_simple_future(Efl_Loop *loop);
static void _test2_failed_future(Efl_Loop *loop);
static void _test3_cancelled_future(Efl_Loop *loop);
static void _test4_chained_future(Efl_Loop *loop);

/* ----------------------- Generic helper methods ---------------------- */

/*
 * This simple method prints the content of a value and passes it on.
 */
static Eina_Value
_value_print(void *data EINA_UNUSED, const Eina_Value value)
{
   char *str = eina_value_to_string(&value);
   printf("  Success callback: Promise resolved to '%s'\n", str);
   free(str);

   return value;
}

/*
 * This will be called if a promise is cancelled.
 */
static void
_promise_cancel(void *data EINA_UNUSED, const Eina_Promise *dead EINA_UNUSED)
{
   printf("  Promise cancellation callback: Promise cancelled\n");
}

/*
 * This method prints the message of the error encountered and returns no value.
 */
static Eina_Value
_error_print(void *data EINA_UNUSED, const Eina_Error error)
{
   printf("  Error callback: Promise encountered error '%s'\n",
          eina_error_msg_get(error));

   return EINA_VALUE_EMPTY;
}

/* ----------------------- Test 1 ---------------------- */

/* Resolve the promise passed through data to a string and cancel the timer */
static void
_test1_resolve(void *data, const Efl_Event *event)
{
   Eina_Promise *promise = (Eina_Promise *)data;

   eina_promise_resolve(promise, eina_value_string_init("Test 1 Delayed Value"));

   efl_del(event->object);
}

/* Launches the next test */
static void
_test1_next_test(void *data, const Eina_Future *dead_future EINA_UNUSED)
{
   Efl_Loop *loop = data;

   printf("  Test 1 finished\n");
   _test2_failed_future(loop);
}

/* TEST 1: Set up a promised future and resolve it from a timer callback */
static void
_test1_simple_future(Efl_Loop *loop)
{
   Eina_Promise *promise;

   // Create a promise
   promise = eina_promise_new(efl_loop_future_scheduler_get(loop),
                              _promise_cancel, NULL);
   printf("Test 1: Waiting for promise to be resolved...\n");

   // This future will call _value_print() when the promise is resolved and
   // execute the next test when the future is destroyed (for whatever reason)
   eina_future_then_easy(eina_future_new(promise),
                         .success = _value_print,
                         .free = _test1_next_test,
                         .data = loop);

   // Set up a regular timer that will trigger after 1s. We use it to
   // simulate a delayed promise resolve.
   efl_add(EFL_LOOP_TIMER_CLASS, loop,
           efl_loop_timer_interval_set(efl_added, 1),
           efl_event_callback_add(efl_added, EFL_LOOP_TIMER_EVENT_TIMER_TICK,
                                  _test1_resolve, promise));
}

/* ----------------------- Test 2 ---------------------- */

/* Reject the passed promise with an specific error and cancel the timer */
static void
_test2_reject(void *data, const Efl_Event *event)
{
   Eina_Promise *promise = (Eina_Promise *)data;

   eina_promise_reject(promise, EINA_ERROR_NOT_IMPLEMENTED);

   efl_del(event->object);
}

/* Launches the next test */
static void
_test2_next_test(void *data, const Eina_Future *dead_future EINA_UNUSED)
{
   Efl_Loop *loop = data;

   printf("  Test 2 finished\n");
   _test3_cancelled_future(loop);
}

/* TEST 2: Set up a promised future and reject it from a timer callback */
static void
_test2_failed_future(Efl_Loop *loop)
{
   Eina_Promise *promise;

   // Create a promise
   promise = eina_promise_new(efl_loop_future_scheduler_get(loop),
                              _promise_cancel, NULL);
   printf("Test 2: Waiting for promise to be rejected...\n");

   // This future will call _value_print() when the promise is resolved.
   // If there is an error, _error_print() is called instead.
   // It then executes the next test when the future is destroyed.
   eina_future_then_easy(eina_future_new(promise),
                         .success = _value_print,
                         .error = _error_print,
                         .free = _test2_next_test,
                         .data = loop);

   // Set up a regular timer that will trigger after 1s. We use it to
   // simulate a delayed promise rejection.
   efl_add(EFL_LOOP_TIMER_CLASS, loop,
           efl_loop_timer_interval_set(efl_added, 1),
           efl_event_callback_add(efl_added, EFL_LOOP_TIMER_EVENT_TIMER_TICK,
                                  _test2_reject, promise));
}

/* ----------------------- Test 3 ---------------------- */

/* Launches the next test */
static void
_test3_next_test(void *data, const Eina_Future *dead_future EINA_UNUSED)
{
   Efl_Loop *loop = data;

   printf("  Test 3 finished\n");
   _test4_chained_future(loop);
}

/* TEST 3: Set up a promised future and then cancel it */
static void
_test3_cancelled_future(Efl_Loop *loop)
{
   Eina_Promise *promise;
   Eina_Future *future;

   // Create a promise
   promise = eina_promise_new(efl_loop_future_scheduler_get(loop),
                              _promise_cancel, NULL);
   future = eina_future_new(promise);
   printf("Test 3: Waiting for promise to be cancelled...\n");

   // This future will call _value_print() when the promise is resolved.
   // If there is an error, _error_print() is called instead.
   // It then executes the next test when the future is destroyed.
   eina_future_then_easy(future,
                         .success = _value_print,
                         .error = _error_print,
                         .free = _test3_next_test,
                         .data = loop);

   // Cancel the future before it has a chance to resolve
   eina_future_cancel(future);
}

/* ----------------------- Test 4 ---------------------- */

/* Resolve the passed promise to an integer with value 1 and cancel the timer */
static void
_test4_resolve(void *data, const Efl_Event *event)
{
   Eina_Promise *promise = (Eina_Promise *)data;

   eina_promise_resolve(promise, eina_value_int_init(1));

   efl_del(event->object);
}

/*
 * A value callback to chain, taking in an int value and returning to chain
 * the int multiplied by two.
 */
static Eina_Value
_chain_multiply_cb(void *data EINA_UNUSED, const Eina_Value value,
                   const Eina_Future *dead_future EINA_UNUSED)
{
   int i;

   if (value.type != EINA_VALUE_TYPE_INT)
     {
        fprintf(stderr, "Expected type 'int', got '%s'\n", value.type->name);
        return value;
     }

   eina_value_get(&value, &i);
   return *eina_value_util_int_new(i * 2);
}

/* This chained callback exits the example */
static Eina_Value
_exit_cb(void *data EINA_UNUSED, const Eina_Value value EINA_UNUSED,
         const Eina_Future *dead_future EINA_UNUSED)
{
   efl_exit(0);

   printf("  Test 4 finished\n");

   return EINA_VALUE_EMPTY;
}

/*
 * TEST 4: Run a future chain where the initial future returns a single value.
 * Each item in the chain then processes this value and passes it to the next item.
 * The _chain_multiply_cb() returns twice the value it gets and the
 * eina_future_cb_console prints a message including the value before passing
 * it on.
 */
static void
_test4_chained_future(Efl_Loop *loop)
{
   Eina_Promise *promise;

   // Create a promise
   promise = eina_promise_new(efl_loop_future_scheduler_get(loop),
                              _promise_cancel, NULL);

   printf("Test 4: Waiting for promise to be resolved...\n");
   // All these methods, eina_future_cb_console() and _chain_multiply_cb(), will
   // be called one after the other when the promise is resolved.
   // Note how the last one is _exit_cb().
   // There are 10 futures chained in total.
   eina_future_chain(eina_future_new(promise),
                     eina_future_cb_console("  Starting chain with value: ", NULL),
                     {.cb = _chain_multiply_cb, .data = NULL},
                     eina_future_cb_console("  Multiplied by 2: ", NULL),
                     {.cb = _chain_multiply_cb, .data = NULL},
                     eina_future_cb_console("  Multiplied by 2: ", NULL),
                     {.cb = _chain_multiply_cb, .data = NULL},
                     eina_future_cb_console("  Multiplied by 2: ", NULL),
                     {.cb = _chain_multiply_cb, .data = NULL},
                     eina_future_cb_console("  Multiplied by 2: ", NULL),
                     {.cb = _exit_cb, .data = NULL});

   // Set up a regular timer that will trigger after 1s. We use it to
   // simulate a delayed promise resolve.
   efl_add(EFL_LOOP_TIMER_CLASS, loop,
           efl_loop_timer_interval_set(efl_added, 1),
           efl_event_callback_add(efl_added, EFL_LOOP_TIMER_EVENT_TIMER_TICK,
                                  _test4_resolve, promise));
}

/* ----------------------- Main ---------------------- */

EAPI_MAIN void
efl_main(void *data EINA_UNUSED, const Efl_Event *ev)
{
   Efl_Loop *loop = ev->object;

   // Start the first test, the others will be launched when this one finishes
   _test1_simple_future(loop);
}

EFL_MAIN()