Add zend_future_t structure to async API

  Introduce Future data structure following coroutine architecture patterns:
  - Inherits from zend_async_event_t for event system integration
  - Contains result/exception storage with debug location tracking
  - Provides resolve method pointer for flexible resolution strategies
  - Supports thread-safe creation parameter
  - Uses function pointer pattern consistent with existing async API
  - Includes stub implementation for disabled async mode

  Structure enables passive result containers that integrate with
  existing callback and replay mechanisms

Author: EdmondDantes

Zend/zend_async_API.c

@@ -48,6 +48,12 @@ static void shutdown_stub(void) {}
 
 static zend_array* get_coroutines_stub(void) { return NULL; }
 
+static zend_future_t* future_create_stub(bool thread_safe, size_t extra_size) 
+{
+	ASYNC_THROW_ERROR("Async API is not enabled");
+	return NULL;
+}
+
 static void add_microtask_stub(zend_async_microtask_t *microtask) {}
 
 static zend_array* get_awaiting_info_stub(zend_coroutine_t *coroutine) { return NULL; }
@@ -97,6 +103,7 @@ zend_async_get_coroutines_t zend_async_get_coroutines_fn = get_coroutines_stub;
 zend_async_add_microtask_t zend_async_add_microtask_fn = add_microtask_stub;
 zend_async_get_awaiting_info_t zend_async_get_awaiting_info_fn = get_awaiting_info_stub;
 zend_async_get_class_ce_t zend_async_get_class_ce_fn = get_class_ce;
+zend_async_future_create_t zend_async_future_create_fn = future_create_stub;
 
 static zend_atomic_bool reactor_lock = {0};
 static char * reactor_module_name = NULL;

Zend/zend_async_API.h

@@ -119,6 +119,11 @@ typedef enum
  * zend_coroutine_t is a Basic data structure that represents a coroutine in the Zend Engine.
  */
 typedef struct _zend_coroutine_s zend_coroutine_t;
+
+/**
+ * zend_future_t is a data structure that represents a future result container.
+ */
+typedef struct _zend_future_s zend_future_t;
 typedef struct _zend_async_context_s zend_async_context_t;
 typedef struct _zend_async_waker_s zend_async_waker_t;
 typedef struct _zend_async_microtask_s zend_async_microtask_t;
@@ -127,6 +132,9 @@ typedef struct _zend_async_iterator_s zend_async_iterator_t;
 typedef struct _zend_fcall_s zend_fcall_t;
 typedef void (*zend_coroutine_entry_t)(void);
 
+/* Future resolve function type */
+typedef void (*zend_future_resolve_t)(zend_future_t *future, zval *value, zend_object *exception, bool transfer_error);
+
 /* Coroutine Switch Handlers */
 typedef struct _zend_coroutine_switch_handler_s zend_coroutine_switch_handler_t;
 typedef struct _zend_coroutine_switch_handlers_vector_s zend_coroutine_switch_handlers_vector_t;
@@ -203,6 +211,7 @@ typedef zend_array* (*zend_async_get_coroutines_t)(void);
 typedef void (*zend_async_add_microtask_t)(zend_async_microtask_t *microtask);
 typedef zend_array* (*zend_async_get_awaiting_info_t)(zend_coroutine_t * coroutine);
 typedef zend_class_entry* (*zend_async_get_class_ce_t)(zend_async_class type);
+typedef zend_future_t* (*zend_async_future_create_t)(bool thread_safe, size_t extra_size);
 
 typedef void (*zend_async_reactor_startup_t)(void);
 typedef void (*zend_async_reactor_shutdown_t)(void);
@@ -963,6 +972,25 @@ struct _zend_coroutine_s {
 	zend_coroutine_switch_handlers_vector_t *switch_handlers;
 };
 
+/**
+ * zend_future_t structure represents a future result container.
+ * It inherits from zend_async_event_t to participate in the event system.
+ */
+struct _zend_future_s {
+	zend_async_event_t event;               /* Event inheritance (first member) */
+	zval result;                            /* Result value (UNDEF = pending) */
+	zend_object *exception;                 /* Exception object (NULL = no error) */
+	
+	/* Debug information */
+	zend_string *filename;                  /* Creation file */
+	uint32_t lineno;                        /* Creation line */
+	zend_string *resolved_filename;         /* Resolution file */
+	uint32_t resolved_lineno;               /* Resolution line */
+
+	/* Resolution method */
+	zend_future_resolve_t resolve;
+};
+
 /**
  * The macro evaluates to TRUE if the coroutine is in a waiting state —
  * either waiting for events or waiting in the execution queue.
@@ -1177,6 +1205,7 @@ ZEND_API extern zend_async_get_coroutines_t zend_async_get_coroutines_fn;
 ZEND_API extern zend_async_add_microtask_t zend_async_add_microtask_fn;
 ZEND_API extern zend_async_get_awaiting_info_t zend_async_get_awaiting_info_fn;
 ZEND_API extern zend_async_get_class_ce_t zend_async_get_class_ce_fn;
+ZEND_API extern zend_async_future_create_t zend_async_future_create_fn;
 
 /* Iterator API */
 ZEND_API extern zend_async_new_iterator_t zend_async_new_iterator_fn;
@@ -1361,6 +1390,10 @@ ZEND_API void zend_async_add_main_coroutine_start_handler(
 
 ZEND_API void zend_async_call_main_coroutine_start_handlers(zend_coroutine_t *main_coroutine);
 
+/* Future API Functions */
+#define ZEND_ASYNC_NEW_FUTURE(thread_safe) zend_async_future_create_fn(thread_safe, 0)
+#define ZEND_ASYNC_NEW_FUTURE_EX(thread_safe, extra_size) zend_async_future_create_fn(thread_safe, extra_size)
+
 END_EXTERN_C()
 
 #define ZEND_ASYNC_IS_ENABLED() zend_async_is_enabled()