Deterministic Observer pattern implementation for safety-critical systems. More...

#include "observer.h"
#include "observer_public_types.h"
#include <stddef.h>
#include <stdint.h>

Include dependency graph for observer.c:

Functions
subscr_status_e	subscribe (observer_cb_t *subscription_table, observer_cb_t cb_2_register, uint8_t subscription_table_size)
	Register a callback in the subscription table (void callbacks). More...

subscr_status_e	unsubscribe (observer_cb_t *subscription_table, observer_cb_t cb_2_remove, uint8_t subscription_table_size)
	Unregister a callback from the subscription table (void callbacks). More...

subscr_status_e	notify (observer_cb_t *subscription_table, uint8_t subscription_table_size)
	Notify all registered callbacks (no argument). More...

subscr_status_e	subscribe_state_change (observer_cb_state_t *subscription_table, observer_cb_state_t cb_2_register, uint8_t subscription_table_size)
	Register a callback with event_state_e argument. More...

subscr_status_e	unsubscribe_state_change (observer_cb_state_t *subscription_table, observer_cb_state_t cb_2_remove, uint8_t subscription_table_size)
	Unregister a callback with event_state_e argument. More...

subscr_status_e	notify_state_change (observer_cb_state_t *subscription_table, uint8_t subscription_table_size, event_state_e state)
	Notify all registered callbacks with event_state_e argument. More...

subscr_status_e	subscribe_u8 (observer_cb_u8_arg_t *subscription_table, observer_cb_u8_arg_t cb_2_register, uint8_t subscription_table_size)
	Register a callback with uint8_t argument. More...

subscr_status_e	unsubscribe_u8 (observer_cb_u8_arg_t *subscription_table, observer_cb_u8_arg_t cb_2_remove, uint8_t subscription_table_size)
	Unregister a callback with uint8_t argument. More...

subscr_status_e	notify_u8 (observer_cb_u8_arg_t *subscription_table, uint8_t subscription_table_size, uint8_t data)
	Notify all registered callbacks with uint8_t argument. More...

Detailed Description

Deterministic Observer pattern implementation for safety-critical systems.

Implements a static, deterministic variant of the Observer pattern suitable for safety-critical and resource-constrained embedded environments.

All API functions:

Validate input parameters.
Return deterministic status codes.
Avoid dynamic memory allocation.
Use single-point return for MISRA C Rule 15.5 compliance.

@thread_safety None of the API functions are reentrant or thread-safe. Caller must ensure synchronization if used concurrently.

Version: 1.0.0

Date: 2025-10-25

@autho niwciu (niwci.nosp@m.u@gm.nosp@m.ail.c.nosp@m.om)

Copyright: Copyright (c) 2025

@safety Designed to meet MISRA C 2012 and ISO 26262 Part 6 software safety goals.

Function Documentation

◆ notify()

subscr_status_e notify	(	observer_cb_t *	subscription_table,
		uint8_t	subscription_table_size
	)

Notify all registered callbacks (no argument).

Invokes all non-NULL callbacks in ascending index order.

Parameters

[in]	subscription_table	Pointer to an array of observer_cb_t.
[in]	subscription_table_size	Table length.

Returns: OBSERVER_OK At least one callback invoked.; OBSERVER_INVALID_ARGUMENT_ERROR Null pointer or zero size.; OBSERVER_TABLE_EMPTY_ERROR No callbacks registered.

Precondition: Valid table pointer of given size.

Postcondition: All active callbacks are executed once. @safety Not reentrant; caller must ensure synchronization. @traceability OBSR-FUNC-003

◆ notify_state_change()

subscr_status_e notify_state_change	(	observer_cb_state_t *	subscription_table,
		uint8_t	subscription_table_size,
		event_state_e	state
	)

Notify all registered callbacks with event_state_e argument.

Calls all valid (non-NULL) callbacks, passing the given event state.

Parameters

[in]	subscription_table	Pointer to array of observer_cb_state_t.
[in]	subscription_table_size	Table length.
[in]	state	Event state passed to callbacks.

Returns: OBSERVER_OK At least one callback invoked.; OBSERVER_INVALID_ARGUMENT_ERROR Null pointer or zero size.; OBSERVER_TABLE_EMPTY_ERROR No callbacks registered.

Precondition: Valid table pointer of given size.

Postcondition: All registered callbacks called with state. @safety Not reentrant; caller must ensure synchronization. @traceability OBSR-FUNC-006

◆ notify_u8()

subscr_status_e notify_u8	(	observer_cb_u8_arg_t *	subscription_table,
		uint8_t	subscription_table_size,
		uint8_t	data
	)

Notify all registered callbacks with uint8_t argument.

Invokes all registered callbacks, passing a uint8_t data value.

Parameters

[in]	subscription_table	Pointer to array of observer_cb_u8_arg_t.
[in]	subscription_table_size	Table length.
[in]	data	Data argument passed to each callback.

Returns: OBSERVER_OK At least one callback invoked.; OBSERVER_INVALID_ARGUMENT_ERROR Null pointer or zero size.; OBSERVER_TABLE_EMPTY_ERROR No callbacks registered.

Precondition: Valid table pointer of given size.

Postcondition: All registered callbacks called with data. @safety Not reentrant; caller must ensure synchronization. @traceability OBSR-FUNC-009

◆ subscribe()

subscr_status_e subscribe	(	observer_cb_t *	subscription_table,
		observer_cb_t	cb_2_register,
		uint8_t	subscription_table_size
	)

Register a callback in the subscription table (void callbacks).

Registers a callback function in the provided subscription table. If the callback is already present, it is not added again.

Parameters

[in,out]	subscription_table	Pointer to an array of observer_cb_t.
[in]	cb_2_register	Callback function to register.
[in]	subscription_table_size	Number of entries in the table (must be > 0).

Returns: OBSERVER_OK Callback registered or already present.; OBSERVER_INVALID_ARGUMENT_ERROR Null pointer or zero size.; OBSERVER_TABLE_FULL_ERROR No free slot available.

Precondition: subscription_table points to a valid array of given size.

Postcondition: On success, cb_2_register is stored in the table. @safety Not reentrant; caller must ensure synchronization. @traceability OBSR-FUNC-001

◆ subscribe_state_change()

subscr_status_e subscribe_state_change	(	observer_cb_state_t *	subscription_table,
		observer_cb_state_t	cb_2_register,
		uint8_t	subscription_table_size
	)

Register a callback with event_state_e argument.

Registers a state-change callback in the given subscription table. Prevents duplicate registrations.

Parameters

[in,out]	subscription_table	Pointer to array of observer_cb_state_t.
[in]	cb_2_register	Callback function to register.
[in]	subscription_table_size	Table length (must be > 0).

Returns: OBSERVER_OK Callback registered or already present.; OBSERVER_INVALID_ARGUMENT_ERROR Null pointer or zero size.; OBSERVER_TABLE_FULL_ERROR No free slot available.

Precondition: Valid table pointer of given size.

Postcondition: Callback stored on success. @safety Not reentrant; caller must ensure synchronization. @traceability OBSR-FUNC-004

◆ subscribe_u8()

subscr_status_e subscribe_u8	(	observer_cb_u8_arg_t *	subscription_table,
		observer_cb_u8_arg_t	cb_2_register,
		uint8_t	subscription_table_size
	)

Register a callback with uint8_t argument.

Registers a callback in the given table if not already present.

Parameters

[in,out]	subscription_table	Pointer to array of observer_cb_u8_arg_t.
[in]	cb_2_register	Callback to register.
[in]	subscription_table_size	Table length (must be > 0).

Returns: OBSERVER_OK Callback registered or already present.; OBSERVER_INVALID_ARGUMENT_ERROR Null pointer or zero size.; OBSERVER_TABLE_FULL_ERROR No free slot.

Precondition: Valid table pointer of given size.

Postcondition: Callback stored on success. @safety Not reentrant; caller must ensure synchronization. @traceability OBSR-FUNC-007

◆ unsubscribe()

subscr_status_e unsubscribe	(	observer_cb_t *	subscription_table,
		observer_cb_t	cb_2_remove,
		uint8_t	subscription_table_size
	)

Unregister a callback from the subscription table (void callbacks).

Removes a registered callback and compacts the table by shifting subsequent entries left.

Parameters

[in,out]	subscription_table	Pointer to an array of observer_cb_t.
[in]	cb_2_remove	Callback function to remove.
[in]	subscription_table_size	Table length.

Returns: OBSERVER_OK Callback successfully removed.; OBSERVER_TABLE_EMPTY_ERROR Callback not found.; OBSERVER_INVALID_ARGUMENT_ERROR Null pointer or zero size.

Precondition: Valid table pointer of given size.

Postcondition: Table compacted after removal. @safety Not reentrant; caller must ensure synchronization. @traceability OBSR-FUNC-002

◆ unsubscribe_state_change()

subscr_status_e unsubscribe_state_change	(	observer_cb_state_t *	subscription_table,
		observer_cb_state_t	cb_2_remove,
		uint8_t	subscription_table_size
	)

Unregister a callback with event_state_e argument.

Removes a previously registered callback from the table and compacts it.

Parameters

[in,out]	subscription_table	Pointer to array of observer_cb_state_t.
[in]	cb_2_remove	Callback function to remove.
[in]	subscription_table_size	Table length.

Returns: OBSERVER_OK Callback removed.; OBSERVER_TABLE_EMPTY_ERROR Callback not found.; OBSERVER_INVALID_ARGUMENT_ERROR Null pointer or zero size.

Precondition: Valid table pointer of given size.

Postcondition: Table compacted after removal. @safety Not reentrant; caller must ensure synchronization. @traceability OBSR-FUNC-005

◆ unsubscribe_u8()

subscr_status_e unsubscribe_u8	(	observer_cb_u8_arg_t *	subscription_table,
		observer_cb_u8_arg_t	cb_2_remove,
		uint8_t	subscription_table_size
	)

Unregister a callback with uint8_t argument.

Removes a callback from the table and shifts subsequent entries left.

Parameters

[in,out]	subscription_table	Pointer to array of observer_cb_u8_arg_t.
[in]	cb_2_remove	Callback to remove.
[in]	subscription_table_size	Table length.

Returns: OBSERVER_OK Callback removed.; OBSERVER_TABLE_EMPTY_ERROR Callback not found.; OBSERVER_INVALID_ARGUMENT_ERROR Null pointer or zero size.

Precondition: Valid table pointer of given size.

Postcondition: Table compacted after removal. @safety Not reentrant; caller must ensure synchronization. @traceability OBSR-FUNC-008

Functions

Detailed Description

Function Documentation

◆ notify()

◆ notify_state_change()

◆ notify_u8()

◆ subscribe()

◆ subscribe_state_change()

◆ subscribe_u8()

◆ unsubscribe()

◆ unsubscribe_state_change()

◆ unsubscribe_u8()