Queue.h

00001 // downloaded from: https://gist.github.com/ArnonEilat/4471278
00002 
00003 #include <stdlib.h>
00004 #include <stdio.h>
00005 
00006 #define TRUE  1
00007 #define FALSE   0
00008 #define QUEUE_STRING_LENGTH 40
00009 
00010 /* a link in the queue, holds the info and point to the next Node*/
00011 typedef struct {
00012     int length;
00013     char payload[QUEUE_STRING_LENGTH-1];  // null-terminated string, max 256 characters long, this may be JSON or any other format, depending on the application
00014 } DATA;
00015 
00016 typedef struct Node_t {
00017     DATA data;
00018     struct Node_t *prev;
00019 } NODE;
00020 
00021 /* the HEAD of the Queue, hold the amount of node's that are in the queue*/
00022 typedef struct Queue {
00023     NODE *head;
00024     NODE *tail;
00025     int size;
00026     int limit;
00027 } Queue;
00028 
00029 Queue *ConstructQueue(int limit);
00030 void DestructQueue(Queue *queue);
00031 int Enqueue(Queue *pQueue, NODE *item);
00032 NODE *Dequeue(Queue *pQueue);
00033 int isEmpty(Queue* pQueue);
00034 
00035 Queue *ConstructQueue(int limit) {
00036     Queue *queue = (Queue*) malloc(sizeof (Queue));
00037     if (queue == NULL) {
00038         return NULL;
00039     }
00040     if (limit <= 0) {
00041         limit = 65535;
00042     }
00043     queue->limit = limit;
00044     queue->size = 0;
00045     queue->head = NULL;
00046     queue->tail = NULL;
00047 
00048     return queue;
00049 }
00050 
00051 void DestructQueue(Queue *queue) {
00052     NODE *pN;
00053     while (!isEmpty(queue)) {
00054         pN = Dequeue(queue);
00055         free(pN);
00056     }
00057     free(queue);
00058 }
00059 
00060 int Enqueue(Queue *pQueue, NODE *item) {
00061     /* Bad parameter */
00062     if ((pQueue == NULL) || (item == NULL)) {
00063         return FALSE;
00064     }
00065     // if(pQueue->limit != 0)
00066     if (pQueue->size >= pQueue->limit) {
00067         return FALSE;
00068     }
00069     /*the queue is empty*/
00070     item->prev = NULL;
00071     if (pQueue->size == 0) {
00072         pQueue->head = item;
00073         pQueue->tail = item;
00074 
00075     } else {
00076         /*adding item to the end of the queue*/
00077         pQueue->tail->prev = item;
00078         pQueue->tail = item;
00079     }
00080     pQueue->size++;
00081     return TRUE;
00082 }
00083 
00084 NODE * Dequeue(Queue *pQueue) {
00085     /*the queue is empty or bad param*/
00086     NODE *item;
00087     if (isEmpty(pQueue))
00088         return NULL;
00089     item = pQueue->head;
00090     pQueue->head = (pQueue->head)->prev;
00091     pQueue->size--;
00092     return item;
00093 }
00094 
00095 int isEmpty(Queue* pQueue) {
00096     if (pQueue == NULL) {
00097         return FALSE;
00098     }
00099     if (pQueue->size == 0) {
00100         return TRUE;
00101     } else {
00102         return FALSE;
00103     }
00104 }
00105 /*
00106 int main() {
00107     int i;
00108     Queue *pQ = ConstructQueue(7);
00109     NODE *pN;
00110 
00111     for (i = 0; i < 9; i++) {
00112         pN = (NODE*) malloc(sizeof (NODE));
00113         pN->data.info = 100 + i;
00114         Enqueue(pQ, pN);
00115     }
00116 
00117     while (!isEmpty(pQ)) {
00118         pN = Dequeue(pQ);
00119         printf("\nDequeued: %d", pN->data);
00120         free(pN);
00121     }
00122     DestructQueue(pQ);
00123     return (EXIT_SUCCESS);
00124 }
00125 
00126 */