static-data-structures/queue.c

   1 #include <stdio.h>
   2
   3 #define MAX_QUEUE_SIZE 16
   4
   5 struct data {
   6         int code;
   7 };
   8
   9 struct queue {
  10         struct data data[MAX_QUEUE_SIZE];
  11         int first;
  12         int last;
  13 };
  14
  15 static void queue_init(struct queue *queue)
  16 {
  17         queue->first = queue->last = 0;
  18 }
  19
  20 static int queue_empty(const struct queue *queue)
  21 {
  22         return queue->first == queue->last;
  23 }
  24
  25 static int queue_insert(struct queue *queue, struct data *data)
  26 {
  27         if (queue->last == MAX_QUEUE_SIZE)
  28                 return -1;
  29
  30         queue->data[queue->last] = *data;
  31         queue->last++;
  32
  33         return 0;
  34 }
  35
  36 static int queue_remove(struct queue *queue, struct data *ret)
  37 {
  38         int i;
  39
  40         if (queue_empty(queue))
  41                 return -1;
  42
  43         if (ret)
  44                 *ret = queue->data[queue->first];
  45
  46         queue->last--;
  47         for (i = queue->first; i < queue->last; i++)
  48                 queue->data[i] = queue->data[i + 1];
  49
  50         return 0;
  51 }
  52
  53 static void queue_print(const struct queue *queue)
  54 {
  55         int i;
  56
  57         if (queue_empty(queue))
  58                 return;
  59
  60         for (i = queue->first; i < queue->last; i++)
  61                 printf("%d ", queue->data[i].code);
  62         printf("\n");
  63 }
  64
  65 static void fill_data(struct data *data, int code)
  66 {
  67         data->code = code;
  68 }
  69
  70 int main(void)
  71 {
  72         struct queue queue;
  73         struct data data1, data2, data3, data_ret;
  74
  75         queue_init(&queue);
  76
  77         if (queue_empty(&queue))
  78                 printf("Queue is empty\n");
  79         else
  80                 printf("Queue is not empty\n");
  81
  82         fill_data(&data1, 0);
  83         fill_data(&data2, 1);
  84         fill_data(&data3, 2);
  85
  86         queue_insert(&queue, &data1);
  87         queue_insert(&queue, &data2);
  88         queue_insert(&queue, &data3);
  89
  90         if (queue_empty(&queue))
  91                 printf("Queue is empty\n");
  92         else
  93                 printf("Queue is not empty\n");
  94
  95         queue_print(&queue);
  96
  97         queue_remove(&queue, &data_ret);
  98         printf("Item removed: %d\n", data_ret.code);
  99
 100         queue_print(&queue);
 101
 102         return 0;
 103 }