commit c3513b192be31af746c5af46aa514e169a5abaea
Author: lukas <lukas.heiligenbrunner@gmail.com>
Date:   Tue Apr 28 21:25:03 2020 +0200

    init

diff --git a/double_chained_functions.c b/double_chained_functions.c
new file mode 100755
index 0000000..65d8c55
--- /dev/null
+++ b/double_chained_functions.c
@@ -0,0 +1,129 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include "double_chained_functions.h"
+
+messdaten* insertFirst (messdaten* firstelem, messdaten* newelement)
+{
+  if (firstelem != NULL)
+    {
+      newelement->next = firstelem;
+      newelement->prev = firstelem->prev;
+      firstelem->prev = newelement;
+    }
+  else
+    {
+      newelement->next = NULL;
+      newelement->prev = newelement;
+    }
+
+  return (newelement);
+}
+
+messdaten* insertLast (messdaten* firstelem, messdaten* newelement)
+{
+  if (firstelem != NULL)
+    {
+      newelement->prev = firstelem->prev;
+      firstelem->prev = newelement;
+      newelement->prev->next = newelement;
+      newelement->next = NULL;
+    }
+
+  else
+    {
+      firstelem = insertFirst (firstelem, newelement);
+    }
+
+  return (firstelem);
+}
+
+messdaten* insertPos (messdaten* firstelem, messdaten* newelement, int pos)
+{
+  int i = 0;
+  messdaten* temp = firstelem;
+
+  if (pos == 0)
+    {
+      firstelem = insertFirst (firstelem, newelement);
+    }
+
+  else
+    {
+      while (temp->next != NULL && i < (pos - 2))
+	{
+	  temp = temp->next;
+	  i++;
+	}
+
+      if (temp->next != NULL)
+	{
+	  newelement->next = temp->next;
+	  temp->next = newelement;
+	  newelement->prev = temp->next->prev;
+	  temp->next->prev = newelement;
+	}
+      else
+	{
+	  firstelem = insertLast (firstelem, newelement);
+	  fprintf (stderr,"llfunct:insertPos->Warning Position is not existing. Element is added to the end of the list!!\n");
+	}
+    }
+
+  return (firstelem);
+}
+
+messdaten* deleteFirst (messdaten* firstelem)
+{
+  messdaten* n = firstelem;
+
+  firstelem = n->next;
+  firstelem->prev = n->prev;
+  free (n);
+
+  return (firstelem);
+}
+
+messdaten* deleteLast (messdaten* firstelem)
+{
+  messdaten* temp = firstelem->prev;
+
+  firstelem->prev = firstelem->prev->prev;
+  free ((firstelem->prev->next));
+  firstelem->prev->next = NULL;
+
+  return (firstelem);
+}
+
+messdaten* deletePos (messdaten* firstelem, int pos)
+{
+  int i = 0;
+  messdaten* temp = firstelem;
+  messdaten* tempsec;
+
+  while (i < (pos - 2))
+    {
+      temp = temp->next;
+      i++;
+    }
+
+  tempsec = temp->next->next;
+  tempsec->prev = temp;
+
+  free (temp->next);
+  temp->next = tempsec;
+
+  return (firstelem);
+}
+
+messdaten* deleteAll (messdaten* firstelem)
+{
+  messdaten* temp;
+
+  while (firstelem->next != NULL)
+    {
+      temp = firstelem;
+      firstelem = temp->next;
+      free (temp);
+    }
+  return (firstelem);
+}
diff --git a/double_chained_functions.h b/double_chained_functions.h
new file mode 100755
index 0000000..c0f729c
--- /dev/null
+++ b/double_chained_functions.h
@@ -0,0 +1,74 @@
+/*
+ * double_chained_functions.h
+ *
+ *  Created on: 14.11.2017
+ *      Author: lukas
+ */
+
+#ifndef DOUBLE_CHAINED_FUNCTIONS_H_
+#define DOUBLE_CHAINED_FUNCTIONS_H_
+
+typedef struct mydata
+{
+  char sensorname[10];
+  float messwert;
+} mydata;
+
+typedef struct messdaten
+{
+  struct messdaten * next;
+  struct messdaten * prev;
+  struct mydata data;
+} messdaten;
+
+/* functon to insert the first element
+ * in: firstelem; newelement
+ * out: newelement
+ * changed: firstelem
+ */
+messdaten* insertFirst (messdaten* firstelem, messdaten* newelement);
+
+/* functon to insert the last element
+ * in: firstelem; newelement
+ * out: newelement
+ * changed: lastelement
+ */
+messdaten* insertLast (messdaten* firstelem, messdaten* newelement);
+
+/* functon to insert the element on a specific position
+ * in: firstelem; newelement; position
+ * out: newelement
+ * changed: one more item in chained list...
+ */
+messdaten* insertPos (messdaten* firstelem, messdaten* newelement, int pos);
+
+/* functon to delete the first element
+ * in: firstelem;
+ * out: newelement
+ * changed: firstelem
+ */
+messdaten*
+deleteFirst (messdaten* firstelem);
+
+/* functon to delete the last element
+ * in: firstelem
+ * out: newelement
+ * changed: lastelement
+ */
+messdaten* deleteLast (messdaten* firstelem);
+
+/* functon to delete the element of a specific element
+ * in: firstelem; newelement
+ * out: newelement
+ * changed: firstelem
+ */
+messdaten* deletePos (messdaten* firstelem, int pos);
+
+/* functon to delete all the list elements
+ * in: firstelem
+ * out: newelement
+ * changed: the whole list
+ */
+messdaten* deleteAll (messdaten* firstelem);
+
+#endif /* DOUBLE_CHAINED_FUNCTIONS_H_ */
diff --git a/double_chained_list.c b/double_chained_list.c
new file mode 100755
index 0000000..652b792
--- /dev/null
+++ b/double_chained_list.c
@@ -0,0 +1,55 @@
+/*
+ ============================================================================
+ Name        : double_chained_list.c
+ Author      : 
+ Version     :
+ Copyright   : Your copyright notice
+ Description : Hello World in C, Ansi-style
+ ============================================================================
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include "double_chained_functions.h"
+
+int main (void)
+{
+
+  messdaten * head;
+  messdaten * erste;
+  messdaten * zweite;
+  messdaten * dritte;
+
+  head = malloc (sizeof(messdaten));
+  erste = malloc (sizeof(messdaten));
+  zweite = malloc (sizeof(messdaten));
+  dritte = malloc (sizeof(messdaten));
+  if (head == NULL || erste == NULL || zweite == NULL || dritte == NULL)
+    {
+      return EXIT_FAILURE;
+    }
+
+  head = insertLast (head, dritte);
+  head = insertPos (head, erste, 1);
+  head = insertPos (head, zweite, 2);
+
+  erste->data.messwert = 42;
+  zweite->data.messwert = 2;
+  dritte->data.messwert = 3;
+
+  printf ("Messwert von head: >%f<\n", head->data.messwert);
+  printf ("Messwert von head next: >%f<\n", head->next->data.messwert);
+  printf ("Messwert von head next next: >%f<\n",
+	  head->next->next->data.messwert);
+  printf ("Messwert von head next next: >%f<\n\n",head->next->next->next->data.messwert);
+
+  printf ("Messwert von head >%f<\n", head->data.messwert);
+  printf ("Messwert von erste: >%f<\n", erste->data.messwert);
+  printf ("Messwert von zweite: >%f<\n", zweite->data.messwert);
+  printf ("Messwert von zweite: >%f<\n", dritte->data.messwert);
+
+  deleteAll (head);
+
+  return EXIT_SUCCESS;
+}
+