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  1.  
  2. $ cat new.c
  3. #include <stdbool.h>
  4. #include <stdio.h>
  5. #include <stdlib.h>
  6. #include <string.h>
  8. #define pp(x) printf("%s = %p\n", #x, x);
  9. #define pi(x) printf("%s = %d\n", #x, x);
  10. #define pc(x) printf("%s = %c\n", #x, x);
  12. // A C program to demonstrate linked list based implementation of queue
  13. // A linked list (LL) node to store a queue entry
  14. int index_start = -1;
  15. int ref_start = 0;
  16. struct QNode
  17. {
  18. int index;
  19. int ref;
  20. struct QNode *next;
  21. };
  23. // The queue, front stores the front node of LL and rear stores ths
  24. // last node of LL
  25. struct Queue
  26. {
  27. struct QNode *front, *rear;
  28. };
  30. // A utility function to create a new linked list node.
  31. struct QNode* newNode(void)
  32. {
  33. struct QNode *temp = (struct QNode*)malloc(sizeof(struct QNode));
  34. temp->index = index_start++;
  35. temp->ref = ref_start++;
  36. temp->next = NULL;
  37. return temp;
  38. }
  40. // A utility function to create an empty queue
  41. struct Queue *createQueue()
  42. {
  43. struct Queue *q = (struct Queue*)malloc(sizeof(struct Queue));
  44. q->front = q->rear = NULL;
  45. return q;
  46. }
  48. void store_asm(struct Queue *q)
  49. {
  50. // Create a new LL node
  51. struct QNode *temp = newNode();
  53. // If queue is empty, then new node is front and rear both
  54. if (q->rear == NULL)
  55. {
  56. q->front = q->rear = temp;
  57. return;
  58. }
  60. // Add the new node at the end of queue and change rear
  61. q->rear->next = temp;
  62. q->rear = temp;
  63. }
  65. struct QNode * load_asm(struct Queue **q)
  66. {
  67. // If queue is empty, return NULL.
  68. if ((q) == NULL) return NULL;
  69. if ((*q) == NULL) return NULL;
  70. if ((*q)->front == NULL)
  71. return NULL;
  73. // Store previous front and move front one node ahead
  74. struct QNode *temp = (*q)->front;
  75. (*q)->front = (*q)->front->next;
  77. // If front becomes NULL, then change rear also as NULL
  78. if ((*q)->front == NULL)
  79. (*q)->rear = NULL;
  80. return temp;
  81. }
  83. int queue_add(struct Queue **q) {
  84. if (!(*q)) (*q) = createQueue();
  85. store_asm((*q));
  86. return 0;
  87. }
  89. struct Queue * list = NULL;
  90. int main(void) {
  91. index_start = 0;
  92. ref_start = 1;
  93. queue_add(&list);
  94. queue_add(&list);
  95. queue_add(&list);
  96. struct QNode * p = list->front;
  97. while(p) {
  98. printf("%d -> %d\n", p->index, p->ref);
  99. p = p->next;
  100. }
  101. puts("NULL");
  102. return 0;
  103. }
  105. $ gcc new.c -o new
  108. $ ./new
  109. 0 -> 1
  110. 1 -> 2
  111. 2 -> 3
  112. NULL
  113.  
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