queue.c File Reference

Generic FIFO queue implementation for embedded safety-critical use. More...

#include "queue.h"

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Macros
#define	PRIVATE   static

Functions
PRIVATE void	copy_bytes (uint8_t *dst, const uint8_t *src, uint16_t size)
	Deterministic byte-wise copy of memory. More...
queue_status_t	queue_init (queue_t *q, void *buffer, uint16_t element_size, uint16_t capacity)
	Initialize a queue. More...
queue_status_t	queue_push (queue_t *q, const void *item)
	Push an element into the queue. More...
queue_status_t	queue_pop (queue_t *q, void *item)
	Pop an element from the queue. More...
bool	queue_is_empty (const queue_t *q)
	Check whether queue is empty. More...
bool	queue_is_full (const queue_t *q)
	Check whether queue is full. More...

Detailed Description

Generic FIFO queue implementation for embedded safety-critical use.

Version

1.0.2

Date

2025-10-26

Provides deterministic enqueue/dequeue operations on a caller-supplied memory buffer. Implementation uses explicit byte-wise copying and avoids standard library dependencies to ensure deterministic behavior.

MISRA Deviation: DV-QUEUE-001 (Rule 11.4) Controlled cast from void* to uint8_t* for raw byte access. Safe because data is not type-reinterpreted.

Note

Internal helper function copy_bytes(uint8_t*, const uint8_t*, uint16_t) is tested indirectly via DV_QUEUE_001 unit tests, including:

• pushing/popping int, struct, char array elements,
• wrap-around behavior,
• zero-byte edge case,
• NULL pointer handling.

Macro Definition Documentation

PRIVATE

#define PRIVATE   static

Function Documentation

copy_bytes()

PRIVATE void copy_bytes	(	uint8_t *	dst,
		const uint8_t *	src,
		uint16_t	size
	)

Deterministic byte-wise copy of memory.

Parameters

[out]	dst	Destination buffer.
[in]	src	Source buffer.
[in]	size	Number of bytes to copy.

Used internally by queue_push/queue_pop to implement type-agnostic element storage. The PRIVATE macro controls visibility:

• static in production builds
• non-static in UNIT_TESTS build for test coverage

Note

MISRA Deviation DV-QUEUE-001: controlled cast for raw memory access.

Branch with NULL pointers is exercised indirectly in unit tests DV_QUEUE_001.

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queue_init()

queue_status_t queue_init	(	queue_t *	q,
		void *	buffer,
		uint16_t	element_size,
		uint16_t	capacity
	)

Initialize a queue.

Parameters

[in,out]	q	Pointer to queue control structure.
[in]	buffer	Pointer to storage buffer.
[in]	element_size	Element size in bytes (>0).
[in]	capacity	Number of elements (>0).

Return values

QUEUE_OK	Successful initialization.
QUEUE_ERROR	Invalid parameters.

queue_is_empty()

bool queue_is_empty

(

const queue_t *

q

)

Check whether queue is empty.

Parameters

[in]

q

Pointer to queue instance.

Returns

true if empty, false otherwise.

queue_is_full()

bool queue_is_full

(

const queue_t *

q

)

Check whether queue is full.

Parameters

[in]

q

Pointer to queue instance.

Returns

true if full, false otherwise.

queue_pop()

queue_status_t queue_pop	(	queue_t *	q,
		void *	item
	)

Pop an element from the queue.

Parameters

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

Return values

QUEUE_OK	Success.
QUEUE_EMPTY	Queue empty.
QUEUE_ERROR	Invalid parameters.

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queue_push()

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

Push an element into the queue.

Parameters

[in,out]	q	Pointer to queue instance.
[in]	item	Pointer to data to add (element_size bytes).

Return values

QUEUE_OK	Success.
QUEUE_FULL	Queue full.
QUEUE_ERROR	Invalid parameters.

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