cbuf

README.md

TBD

cbuf.c

#include <assert.h>
#include <stdlib.h>
#include <stdio.h>

#include "cbuf.h"

uint8_t buf[16];

int main() {
	struct cbuf cbuf;
	size_t cur_len = 0;
	uint8_t put_val = 0;
	uint8_t get_val = 0;

	cbuf_init(&cbuf, buf, sizeof buf);

	while (true) {
		if (cur_len == 0) {
			assert(cbuf_is_empty(&cbuf));
		}
		if (cur_len == sizeof buf) {
			assert(cbuf_is_full(&cbuf));
		}

		if (rand() & 1) {
			if (!cbuf_is_empty(&cbuf)) {
				uint8_t val = cbuf_get(&cbuf);
				assert(val == get_val++);
				cur_len--;
				printf("%u len: %u\n",
				       (unsigned)val, (unsigned)
				       cur_len);
			}
		} else {
			if (!cbuf_is_full(&cbuf)) {
				cbuf_put(&cbuf, put_val++);
				cur_len++;
			}
		}
	}


	return 0;
}

cbuf.h

#include <stddef.h>
#include <stdint.h>
#include <stdbool.h>
#include <string.h>

/* TODO: Fix on 64 architecture */
#define CBUF_DATA_BIT (1 << 31)

/**
 * Char circular buffer
 */
struct cbuf {
	uint8_t *data;
	size_t size;
	size_t start;
	size_t end;
};


static inline
bool cbuf_is_empty(struct cbuf* cbuf)
{
	return cbuf->start == cbuf->end;
}

static inline
bool cbuf_is_full(struct cbuf* cbuf)
{
	return (cbuf->start ^ cbuf->end) == CBUF_DATA_BIT;
}

static inline
uint8_t cbuf_get(struct cbuf* cbuf)
{
	uint8_t ret = cbuf->data[cbuf->start & ~CBUF_DATA_BIT];

	cbuf->start++;

	if ((cbuf->start & ~CBUF_DATA_BIT) >= cbuf->size) {
		cbuf->start -= cbuf->size;
		cbuf->start ^= CBUF_DATA_BIT;
	}

	return ret;
}

static inline
void cbuf_put(struct cbuf* cbuf, uint8_t byte)
{
	cbuf->data[cbuf->end & ~CBUF_DATA_BIT] = byte;

	cbuf->end++;

	if ((cbuf->end & ~CBUF_DATA_BIT) >= cbuf->size) {
		cbuf->end -= cbuf->size;
		cbuf->end ^= CBUF_DATA_BIT;
	}
}

static inline
void cbuf_init(struct cbuf* cbuf, uint8_t* data, size_t size)
{
	memset(cbuf, 0, sizeof(*cbuf));
	cbuf->data = data;
	cbuf->size = size;
}

Makefile

cbuf: cbuf.h cbuf.c
	gcc -O3 -std=gnu99 cbuf.c -o cbuf