Queue Module

Deterministic FIFO queue for safety-critical embedded systems. More...

Collaboration diagram for Queue Module:

Modules
	Queue Internal Functions
	Internal helper functions for the queue module (not part of public API).

Files
file	queue.c
	Generic FIFO queue implementation for embedded safety-critical use.

Data Structures
struct	queue_t
	FIFO queue control structure. More...

Enumerations
enum	queue_status_t { QUEUE_OK = 0U , QUEUE_FULL = 1U , QUEUE_EMPTY = 2U , QUEUE_ERROR = 3U }
	Queue operation status codes. More...

Functions
queue_status_t	queue_init (queue_t *q, void *buffer, uint16_t buffer_element_size, uint16_t queue_capacity)
	Initialize a queue instance. More...
queue_status_t	queue_push (queue_t *q, const void *item)
	Push (enqueue) one element into the queue. More...
queue_status_t	queue_pop (queue_t *q, void *item)
	Pop (dequeue) one element from the queue. More...
bool	queue_is_empty (const queue_t *q)
	Check if queue is empty. More...
bool	queue_is_full (const queue_t *q)
	Check if queue is full. More...

Detailed Description

Deterministic FIFO queue for safety-critical embedded systems.

This module provides a generic, deterministic, and type-agnostic FIFO queue implementation suitable for use in MISRA-C and ISO 26262 compliant projects.

See also

MISRA Compliance

MISRA Compliance

Overview

This module is developed with awareness of MISRA-C:2012 guidelines and is suitable for use in ISO 26262 safety-related applications.

The implementation avoids dynamic memory allocation, recursion, and non-deterministic library calls. All memory accesses are bounded and validated before use.

Controlled Deviations

ID	Rule	Description	Justification
DV-QUEUE-001	MISRA-C:2012 Rule 11.4	Cast between void* and uint8_t* for raw byte copying.	Controlled and justified cast, no aliasing or type reinterpretation. Enables a generic queue implementation. Tested indirectly via DV_QUEUE_001 unit tests, including NULL and edge cases.

See also

docs/compliance/MISRA_Deviations.md

Verification

• Static analysis with MISRA checker: PASSED (no critical violations)
• Unit tests (DV_QUEUE_001): cover int, struct, char array, wrap-around, zero-byte elements, NULL pointer handling
• Code review: APPROVED by Software Safety Architect

Enumeration Type Documentation

queue_status_t

enum queue_status_t

Queue operation status codes.

Enumerator
QUEUE_OK	Operation completed successfully.
QUEUE_FULL	Queue full — push failed.
QUEUE_EMPTY	Queue empty — pop failed.
QUEUE_ERROR	General error — invalid parameters.

Function Documentation

queue_init()

queue_status_t queue_init	(	queue_t *	q,
		void *	buffer,
		uint16_t	buffer_element_size,
		uint16_t	queue_capacity
	)

Initialize a queue instance.

Parameters

[in,out]	q	Pointer to queue control structure.
[in]	buffer	Pointer to caller-supplied storage buffer.
[in]	buffer_element_size	Element size in bytes (must > 0).
[in]	queue_capacity	Number of elements in queue (must > 0).

Return values

QUEUE_OK	Initialization succeeded.
QUEUE_ERROR	Invalid arguments (NULL or 0).

Note

Deterministic and reentrant.

queue_is_empty()

bool queue_is_empty

(

const queue_t *

q

)

Check if queue is empty.

Parameters

[in]

q

Pointer to queue instance.

Returns

true — queue empty or q is NULL.

false — otherwise.

queue_is_full()

bool queue_is_full

(

const queue_t *

q

)

Check if queue is full.

Parameters

[in]

q

Pointer to queue instance.

Returns

true — queue full.

false — otherwise (including q is NULL).

queue_pop()

queue_status_t queue_pop	(	queue_t *	q,
		void *	item
	)

Pop (dequeue) one element from the queue.

Parameters

[in,out]	q	Pointer to queue instance.
[out]	item	Pointer to destination buffer to store element.

Return values

QUEUE_OK	Success.
QUEUE_EMPTY	Queue empty — no element available (item unchanged).
QUEUE_ERROR	Invalid parameters.

Note

Deterministic; no blocking.

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queue_push()

queue_status_t queue_push	(	queue_t *	q,
		const void *	item
	)

Push (enqueue) one element into the queue.

Parameters

[in,out]	q	Pointer to queue instance.
[in]	item	Pointer to element data to add.

Return values

QUEUE_OK	Success.
QUEUE_FULL	Queue already full.
QUEUE_ERROR	Invalid parameters.

Note

Deterministic; no blocking.

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