new Double Link List

#include "stdio.h"
#include "malloc.h"

struct data{
	int value;
	struct data *next, *prev;
}*head, *tail, *current;


void pushHead(int value){
	struct data *newNode = (struct data*)malloc(sizeof(struct data));
	newNode->value = value;
	newNode->prev = newNode->next = NULL;

	if( head == NULL ){
		head = tail = newNode;
		return;
	}

	newNode->next = head;
	head->prev    = newNode;
	head          = newNode;
}

void pushTail(int value){
	struct data *newNode = (struct data*)malloc(sizeof(struct data));
	newNode->value = value;
	newNode->prev = newNode->next = NULL;

	if( head == NULL ){
		head = tail = newNode;
		return;
	}

	tail->next    = newNode;
	newNode->prev = tail;
	tail          = newNode;
}

void popHead(){
	if( head == NULL )
		return;
	if( head == tail ){
		head = tail = NULL;
		return;
	}

	current    = head;
	head       = head->next;
	head->prev = NULL;
	free(current);
}

void popTail(){
	if( head == NULL )
		return;
	if( head == tail ){
		head = tail = NULL;
		return;
	}

	current    = tail;
	tail       = tail->prev;
	tail->next = NULL;
	free(current);
}

void pushMidByIndex(int index, int value){
	if( head == NULL )
		pushHead(value);

	int dataCounter = 0;
	current         = head;

	while( current != NULL ){
		++dataCounter;
		current = current->next;
	}

	if( index > dataCounter+1 )
		return;

	if( index == 1 )
		pushHead(value);
	else if( index == dataCounter+1 )
		pushTail(value);
	else{
		struct data *newNode = (struct data*)malloc(sizeof(struct data));
		newNode->value = value;
		newNode->prev = newNode->next = NULL;

		dataCounter = 0;
		current     = head;

		while( current != NULL ){
			++dataCounter;
			if( dataCounter == index-1 )
				break;
			current = current->next;
		}

		newNode->next = current->next;
		newNode->prev = current;
		current->next->prev = newNode;
		current->next = newNode;
	}
}

void popMidByIndex(int index){
	if( head == NULL )
		return;
	int dataCounter = 0;
	current         = head;

	while( current != NULL ){
		++dataCounter;
		current = current->next;
	}

	if( index > dataCounter )
		return;
	if( index == 1 )
		popHead();
	else if( index == dataCounter )
		popTail();
	else{
		dataCounter = 0;
		current     = head;

		while( current != NULL ){
			++dataCounter;
			if( dataCounter == index )
				break;
			current = current->next;
		}

		current->next->prev = current->prev;
		current->prev->next = current->next;
		current             = NULL;
		free(current);
	}
}

void viewAllData(){
	if( head == NULL )
		return;

	current = head;
	while( current != NULL ){
		printf("%d ", current->value);
		current = current->next;
	}
}

void deleteAllData(){
	while( head != NULL )
		popHead();
}

int main(int argc, char **argv){
	pushHead(1);
	viewAllData();
	return 0;
}