simple_circular_buffer.c

/*
 * LKM Sandbox::Rehearsal
 * <https://github.com/tpiekarski/lkm-sandbox>
 * ---
 * Copyright 2020 Thomas Piekarski <t.piekarski@deloquencia.de>
 *
 * This file is part of LKM Sandbox.
 *
 * LKM Sandbox is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * LKM Sandbox is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with LKM Sandbox. If not, see <https://www.gnu.org/licenses/>.
 *
 */

#include <stdio.h>

#define BUFFER_SIZE 8

static int buffer[BUFFER_SIZE];
static int buffer_length = 0;
static int index_read = 0;
static int index_write = 0;

int read(void)
{
	if (buffer_length == 0) {
		fprintf(stderr, "Can not read, buffer is empty, aborting.\n");

		return -1;
	}

	int value = buffer[index_read++];
	buffer_length--;

	if (index_read == BUFFER_SIZE) {
		index_read = 0;
	}

	return value;
}

void write(int value)
{
	if (buffer_length == BUFFER_SIZE) {
		fprintf(stderr, "Can not write, buffer is full, aborting\n");

		return;
	}

	buffer[index_write++] = value;
	buffer_length++;

	if (index_write == BUFFER_SIZE) {
		index_write = 0;
	}
}

void print_buffer()
{
	printf("Contents of buffer: ");
	for (int i = 0; i < BUFFER_SIZE; i++)
		printf("%i ", buffer[i]);
	printf("\n");
}

int main()
{
	int i = 0;

	print_buffer();

	printf("Writing %i values.\n", BUFFER_SIZE);
	for (i = 1; i < BUFFER_SIZE + 1; i++)
		write(i);

	print_buffer();

	printf("Reading %i values.\n", BUFFER_SIZE);
	for (i = 0; i < BUFFER_SIZE; i++)
		printf("%i ", read());
	printf("\n");

	print_buffer();

	printf("Writing another single value.\n");
	write(9);

	print_buffer();

	return 0;
}