README fixes, Init circular buffer

README.md

@@ -9,7 +9,7 @@ The goal is to develop and test a distributed messaging application based on an
 
 ## Prerequisites
 
-This project was developed for execution on Raspberry Pi Zero W. The rabian image used during development and testing can be found in the repository [`./rasbian_image/`]() directory. Installation directions can be found in Raspberry's website [here](https://www.raspberrypi.org/documentation/installation/installing-images/linux.md).
+This project was developed for execution on Raspberry Pi Zero W. The rabian image used during development and testing can be found in the repository [`./rasbian_image/`](https://gitlab.com/apostolof-ece-auth-gr/authRTESFinalAssignment/tree/master/rasbian_image) directory. Installation directions can be found in Raspberry's website [here](https://www.raspberrypi.org/documentation/installation/installing-images/linux.md).
 
 There are two ways of connecting to the system. By connecting to the port denoted "USB", a new network interface will appear, Raspberry's IP is 192.168.0.1/24 in that network, so you need to configure a static IP for your PC in the range 192.168.0.[2-254].
 
@@ -68,7 +68,7 @@ Reach out to me:
 
 ## License
 
-[![Beerware License](https://img.shields.io/badge/license-beerware%20%F0%9F%8D%BA-blue.svg)](https://gitlab.com/apostolof-ece-auth-gr/authRTESTask1/blob/master/LICENSE.md)
+[![Beerware License](https://img.shields.io/badge/license-beerware%20%F0%9F%8D%BA-blue.svg)](https://gitlab.com/apostolof-ece-auth-gr/authRTESFinalAssignment/blob/master/LICENSE.md)
 
 ---
-<sub><sub>In Mesopotamian mythology, Zaqar is the messenger of the god Sin. He relays these messages to mortals through his power over their dreams and nightmares. </sub></sub>
+<sub>In Mesopotamian mythology, Zaqar is the messenger of the god Sin. He relays these messages to mortals through his power over their dreams and nightmares. </sub>

lib/circ_buff.c

@@ -0,0 +1,126 @@
+#include <stdlib.h>
+#include <stdint.h>
+#include <stddef.h>
+#include <assert.h>
+#include <string.h>
+
+#include "circ_buff.h"
+
+// Defines the circular buffer structure
+struct circ_buf_t {
+	char** buffer;
+	size_t head;
+	size_t tail;
+	size_t max; // of the buffer
+	bool full;
+};
+
+// Private Functions
+
+static void advance_pointer(cbuf_handle_t cbuf) {
+	assert(cbuf);
+
+	if(cbuf->full) {
+		cbuf->tail = (cbuf->tail + 1) % cbuf->max;
+	}
+
+	cbuf->head = (cbuf->head + 1) % cbuf->max;
+
+	// We mark full because we will advance tail on the next time around
+	cbuf->full = (cbuf->head == cbuf->tail);
+}
+
+static void retreat_pointer(cbuf_handle_t cbuf) {
+	assert(cbuf);
+
+	cbuf->full = false;
+	cbuf->tail = (cbuf->tail + 1) % cbuf->max;
+}
+
+// APIs
+
+cbuf_handle_t circ_buf_init(char** buffer, size_t size) {
+	assert(buffer && size);
+
+	cbuf_handle_t cbuf = malloc(sizeof(circ_buf_t));
+	assert(cbuf);
+
+	cbuf->buffer = buffer;
+	cbuf->max = size;
+	circ_buf_reset(cbuf);
+
+	assert(circ_buf_empty(cbuf));
+
+	return cbuf;
+}
+
+void circ_buf_free(cbuf_handle_t cbuf) {
+	assert(cbuf);
+	free(cbuf);
+}
+
+void circ_buf_reset(cbuf_handle_t cbuf) {
+	assert(cbuf);
+
+	cbuf->head = 0;
+	cbuf->tail = 0;
+	cbuf->full = false;
+}
+
+size_t circ_buf_size(cbuf_handle_t cbuf) {
+	assert(cbuf);
+
+	size_t size = cbuf->max;
+
+	if(!cbuf->full) {
+		if(cbuf->head >= cbuf->tail) {
+			size = (cbuf->head - cbuf->tail);
+		}
+		else {
+			size = (cbuf->max + cbuf->head - cbuf->tail);
+		}
+	}
+
+	return size;
+}
+
+size_t circ_buf_capacity(cbuf_handle_t cbuf) {
+	assert(cbuf);
+
+	return cbuf->max;
+}
+
+void circ_buf_put(cbuf_handle_t cbuf, char data) {
+	assert(cbuf && cbuf->buffer);
+
+	strcpy(cbuf->buffer[cbuf->head], data);
+
+	advance_pointer(cbuf);
+}
+
+int circ_buf_get(cbuf_handle_t cbuf, char* data) {
+	assert(cbuf && data && cbuf->buffer);
+
+	int r = -1;
+
+	if(!circ_buf_empty(cbuf)) {
+		strcpy(data, cbuf->buffer[cbuf->tail]);
+		retreat_pointer(cbuf);
+
+		r = 0;
+	}
+
+	return r;
+}
+
+bool circ_buf_empty(cbuf_handle_t cbuf) {
+	assert(cbuf);
+
+	return (!cbuf->full && (cbuf->head == cbuf->tail));
+}
+
+bool circ_buf_full(cbuf_handle_t cbuf) {
+	assert(cbuf);
+
+	return cbuf->full;
+}

lib/circ_buff.h

@@ -0,0 +1,44 @@
+/*
+ * Implementation of a simple circular buffer data structure.
+ * Based on the example and guide found here:
+ * https://embeddedartistry.com/blog/2017/4/6/circular-buffers-in-cc
+*/
+#ifndef CIRC_BUFF_H_
+#define CIRC_BUFF_H_
+
+#include <stdbool.h>
+
+// Circular buffer structure
+typedef struct circ_buf_t circ_buf_t;
+// and handle type
+typedef circ_buf_t* cbuf_handle_t;
+
+// Initializes a circular buffer structure and returns the circular buffer handle.
+// Pass in a storage buffer and size.
+cbuf_handle_t circ_buf_init(char** buffer, size_t size);
+
+// Frees a circular buffer structure. Does not free data buffer!
+void circ_buf_free(cbuf_handle_t cbuf);
+
+// Resets the circular buffer to empty, head == tail. Data not cleared!
+void circ_buf_reset(cbuf_handle_t cbuf);
+
+// Adds data, even if the buffer is full. Old data is overwritten.
+void circ_buf_put(cbuf_handle_t cbuf, char data);
+
+// Retrieves a value from the buffer.
+int circ_buf_get(cbuf_handle_t cbuf, char* data);
+
+// Checks if the buffer is empty.
+bool circ_buf_empty(cbuf_handle_t cbuf);
+
+// Checks if the buffer is full.
+bool circ_buf_full(cbuf_handle_t cbuf);
+
+// Checks the capacity of the buffer.
+size_t circ_buf_capacity(cbuf_handle_t cbuf);
+
+// Checks the number of elements stored in the buffer.
+size_t circ_buf_size(cbuf_handle_t cbuf);
+
+#endif //CIRC_BUFF_H_