dp doubly linked list

linkage.c

@@ -0,0 +1,69 @@
+/*
+ * IGC parser - data linking module (doubly linked datapoint list)
+ * @brief parse IGC file, get all data points, compute average horizontal/vertical speed, print to STDOUT
+ *
+ * As per standard: https://xp-soaring.github.io/igc_file_format/igc_format_2008.html
+ *                  https://xp-soaring.github.io/igc_file_format/igc_fr_specification_with_al8_2023-2-1_0.pdf
+ *
+ * @author xamidev <xamidev@riseup.net>
+ * @license GNU GPL v3
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include "igc.h"
+#include "linkage.h"
+
+struct dp_node* create_datapoint_list()
+{
+	struct dp_node* head = (struct dp_node*)calloc(1, sizeof(struct dp_node));
+
+	head->data = NULL;
+	head->prev = NULL;
+	head->next = NULL;
+	return head;	
+}
+
+void append_datapoint(struct dp_node* list, struct IGC_DataPoint* dp)
+{
+	struct dp_node* new = (struct dp_node*)calloc(1, sizeof(struct dp_node));
+
+	if (list->next == NULL)
+	{
+		list->next = new;
+		
+		new->prev = list;
+		new->next = NULL;
+		new->data = dp;
+		return;
+	}
+
+	while (list->next != NULL)
+	{
+		list = list->next;
+	}
+
+	list->next = new;
+	new->prev = list;
+	new->next = NULL;
+	new->data = dp;
+	return;
+}
+
+void print_datapoint_list(struct dp_node* list)
+{
+	if (list->data == NULL)
+	{
+		// We're at head!
+		list = list->next;
+	}
+
+	while (list->next != NULL)
+	{
+		show_datapoint(list->data);
+		printf(" <-> ");
+		list = list->next;		
+	}
+	puts("NULL");
+	return;
+}