byte_queue

byte_queue

A small caller-buffer-only byte ring queue (FIFO). The queue does no allocation: you supply the backing buffer and capacity at init time. Useful for UART RX/TX buffering, command queues, anything that needs a fixed-size byte FIFO.

API

#include "byte_queue.h"

uint8_t       backing[256];
st_byte_queue q;

bq_init(&q, backing, sizeof backing);

while (uart_byte_available()) {
    if (!bq_put(&q, uart_read())) {
        /* queue full */
        break;
    }
}

uint8_t v;
while (bq_get(&q, &v)) {
    process(v);
}

Function	Purpose
bq_init(q, buffer, cap)	Wrap a caller-supplied buffer in a queue. Call again to re-target the queue at different storage.
bq_clear(q)	Drop every byte (count -> 0). Backing buffer untouched.
bq_count(q)	Bytes currently in the queue.
bq_capacity(q)	Maximum bytes the queue can hold.
bq_is_empty(q)	1 if empty, 0 otherwise.
bq_is_full(q)	1 if full, 0 otherwise.
bq_put(q, v)	Push one byte. Returns 1 on success, 0 if full.
bq_get(q, &out)	Pop one byte into *out. Returns 1 on success, 0 if empty.

Notes

• A separate count field disambiguates the empty / full states, so the queue can hold its full advertised capacity without the classic head == tail ambiguity.
• Not thread-safe / interrupt-safe. If you bq_put from a thread and bq_get from an ISR (or vice versa), wrap the calls in a critical section.

Build the self-test

make test       # from this directory

Prints byte_queue: All OK. on success. The test exercises FIFO order, full / empty boundaries, wrap-around, and the failure modes (put on full, get on empty).

Use in another project

Drop byte_queue.h and byte_queue.c into your sources.

License

MIT.