Eina_Future_Callbacks(3)

NAME
Eina_Future_Callbacks - Eina Future Callbacks

 - Methods and structures dealing with Eina_Future callbacks.

SYNOPSIS

  Data Structures
struct _Eina_Future_Schedule_Entry
A struct that represents an scheduled event.
struct _Eina_Future_Scheduler
This struct is used as a bridge between Eina and the future scheduler.
struct _Eina_Future_Cb_Easy_Desc
A struct with callbacks to be used by eina_future_cb_easy_from_desc() and eina_future_cb_easy()
struct _Eina_Future_Cb_Console_Desc
A struct used to define the prefix and suffix to be printed along side the a future value.
struct _Eina_Future_Cb_Log_Desc
This struct is used by eina_future_cb_log_from_desc() and its contents will be routed to eina_log_print() along side the future value.

  Typedefs
typedef struct _Eina_Future_Cb_Easy_Desc Eina_Future_Cb_Easy_Desc
Convenience wrapper over _Eina_Future_Cb_Easy_Desc.
typedef struct _Eina_Future_Cb_Console_Desc Eina_Future_Cb_Console_Desc
Convenience wrapper over _Eina_Future_Cb_Console_Desc.
typedef struct _Eina_Future_Scheduler Eina_Future_Scheduler
Convenience wrapper over _Eina_Future_Scheduler.
typedef struct _Eina_Future_Schedule_Entry Eina_Future_Schedule_Entry
Convenience wrapper over _Eina_Future_Schedule_Entry.
typedef struct _Eina_Future_Cb_Log_Desc Eina_Future_Cb_Log_Desc
Convenience wrapper over _Eina_Future_Cb_Log_Desc.
typedef Eina_Value(* Eina_Future_Cb) (void *data, const Eina_Value value, const Eina_Future *dead_future)
A callback used to inform that a future was resolved.
typedef void(* Eina_Future_Scheduler_Cb) (Eina_Future *f, Eina_Value value)
A callback used by the Eina_Future_Scheduler to deliver the future operation result.
typedef void(* Eina_Promise_Cancel_Cb) (void *data, const Eina_Promise *dead_promise)
A callback used to inform that a promise was canceled.
typedef Eina_Value(* Eina_Future_Success_Cb) (void *data, const Eina_Value value)
A callback used to inform that the future completed with success.
typedef Eina_Value(* Eina_Future_Error_Cb) (void *data, const Eina_Error error)
A callback used to inform that the future completed with failure.
typedef void(* Eina_Future_Free_Cb) (void *data, const Eina_Future *dead_future)
A callback used to inform that the future was freed and the user should also free the data.

Detailed Description

Methods and structures dealing with Eina_Future callbacks.

Typedef Documentation

  Eina_Future_Cb

A callback used to inform that a future was resolved. Usually this callback is called from a clean context, that is, from the main loop or some platform defined safe context. However there are 2 exceptions:

•   eina_future_cancel() was used, it's called immediately in the context that called cancel using ECANCELED as error.
•   eina_future_then(), eina_future_then_from_desc(), eina_future_chain(), eina_future_chain_array() or similar failed due to invalid pointer or memory allocation. Then the callback is called from the failed context using EINVAL or ENOMEM as errors and dead_future will be NULL.
Parameters
    data The data provided by the user
    value An Eina_Value which contains the operation result. Before using the value, its type must be checked in order to avoid errors. This is needed because if an operation fails the Eina_Value type will be EINA_VALUE_TYPE_ERROR which is a different type than the expected operation result.
    dead_future A pointer to the future that was completed.
Returns
    An Eina_Value to pass to the next Eina_Future in the chain (if any). If there is no need to convert the received value, it's recommended to passthrough the value argument. If you need to convert to a different type or generate a new value, use eina_value_setup() on another Eina_Value and return it. By returning a promise Eina_Value (eina_promise_as_value()) the whole chain will wait until the promise is resolved in order to continue its execution. Note that the value contents must survive this function scope, that is, do not use stack allocated blobs, arrays, structures or types that keep references to memory you give. Values will be automatically cleaned up using eina_value_flush() once they are unused (no more future or futures returned a new value).
Note
    The returned value can be an EINA_VALUE_TYPE_PROMISE! (see eina_promise_as_value() and eina_future_as_value()) In this case the future chain will wait until the promise is resolved.
See also
    eina_future_cancel()
    eina_future_then()
    eina_future_then_from_desc()
    eina_future_then_easy()
    eina_future_chain()
    eina_future_chain_array()
    eina_future_as_value()
    eina_promise_as_value()

  Eina_Future_Scheduler_Cb
A callback used by the Eina_Future_Scheduler to deliver the future operation result.
Parameters
    f The delivered future.
    value The future result
See also
    eina_promise_new()
    Eina_Future_Schedule_Entry
    Eina_Future_Scheduler

  void(* Eina_Promise_Cancel_Cb)(void *data, const Eina_Promise *dead_promise)
A callback used to inform that a promise was canceled. A promise may be canceled by the user calling eina_future_cancel() on any Eina_Future that is part of the chain that uses an Eina_Promise, that will cancel the whole chain and then the promise.
It should stop all asynchronous operations or at least mark them to be discarded instead of resolved. Actually it can't be resolved once canceled since the given pointer dead_promise is now invalid.
Note
    •   This callback is mandatory for a reason, do not provide an empty callback as it'll likely result in memory corruption and invalid access. If impossible to cancel an asynchronous task, then create an intermediate memory to hold Eina_Promise and make it NULL, in this callback. Then prior to resolution check if the pointer is set.
    •   This callback is not called if eina_promise_resolve() or eina_promise_reject() are used. If any cleanup is needed, then call yourself. It's only meant as cancellation, not a general 'free callback'.
Parameters
    data The data provided by the user.
    dead_promise The canceled promise.
See also
    eina_promise_reject()
    eina_promise_resolve()
    eina_future_cancel()

  Eina_Future_Success_Cb
A callback used to inform that the future completed with success. Unlike Eina_Future_Cb this callback is only called if the future operation was successful, this is, no errors occurred (value type differs from EINA_VALUE_TYPE_ERROR) and the value matches _Eina_Future_Cb_Easy_Desc::success_type (if given). In case _Eina_Future_Cb_Easy_Desc::success_type was not supplied (it's NULL) the value type must be checked before using it.
Note
    This function is always called from a safe context (main loop or some platform defined safe context).
Parameters
    data The data provided by the user.
    value The operation result
Returns
    An Eina_Value to pass to the next Eina_Future in the chain (if any). If there is no need to convert the received value, it's recommended to passthrough value argument. If you need to convert to a different type or generate a new value, use eina_value_setup() on another Eina_Value and return it. By returning a promise Eina_Value (eina_promise_as_value()) the whole chain will wait until the promise is resolved in order to continue its execution. Note that the value contents must survive this function scope, that is, do not use stack allocated blobs, arrays, structures or types that keep references to memory you give. Values will be automatically cleaned up using eina_value_flush() once they are unused (no more future or futures returned a new value).
See also
    eina_future_cb_easy_from_desc()
    eina_future_cb_easy()

  Eina_Future_Error_Cb
A callback used to inform that the future completed with failure. Unlike Eina_Future_Success_Cb this function is only called when an error occurs during the future process or when _Eina_Future_Cb_Easy_Desc::success_type differs from the future result. On future creation errors and future cancellation this function will be called from the current context with the following errors: EINVAL, ENOMEM and ECANCELED. Otherwise this function is called from a safe context.
If it was possible to recover from an error this function should return an empty value EINA_VALUE_EMPTY or any other Eina_Value type that differs from EINA_VALUE_TYPE_ERROR. In this case the error will not be reported by the other futures in the chain (if any), otherwise if an Eina_Value type EINA_VALUE_TYPE_ERROR is returned the error will continue to be reported to the other futures in the chain.
Parameters
    data The data provided by the user.
    error The operation error
Returns
    An Eina_Value to pass to the next Eina_Future in the chain (if any). If you need to convert to a different type or generate a new value, use eina_value_setup() on another Eina_Value and return it. By returning a promise Eina_Value (eina_promise_as_value()) the whole chain will wait until the promise is resolved in order to continue its execution. Note that the value contents must survive this function scope, that is, do not use stack allocated blobs, arrays, structures or types that keep references to memory you give. Values will be automatically cleaned up using eina_value_flush() once they are unused (no more future or futures returned a new value).
See also
    eina_future_cb_easy_from_desc()
    eina_future_cb_easy()

  Eina_Future_Free_Cb
A callback used to inform that the future was freed and the user should also free the data. This callback may be called from an unsafe context if the future was canceled or an error occurred.
Note
    This callback is always called, even if Eina_Future_Error_Cb and/or Eina_Future_Success_Cb were not provided, which can also be used to monitor when a future ends.
Parameters
    data The data provided by the user.
    dead_future The future that was freed.
See also
    eina_future_cb_easy_from_desc()
    eina_future_cb_easy()

Author
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