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I'm trying to programm this Queue.

I get an Error at my function calls packet_destroy(p) in the function long queue_store (struct queue_t *q, struct packet_t *p) in line 69 and also in the same function call in line 86 "Implicit declaration of function 'packet_destroy' is invalid in C99"

...now do i have to declare the function struct packet_destroy before i call it in long queue_store (...) ? or what does this error mean in my code?

Code: 

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <limits.h>
#include <string.h>



struct packet_t {
    char *name;
    struct queue_t *queue;
};

struct queue_t {
    char *name;     // Name der Warteschlange
    int size;       // Groesse der Warteschlange
    int entries;    // Anzahl gueltige Eintraege in Warteschlange
    int time;       // Zeitstempel (werden wir erst in P6 beoetigen)
    struct packet_t **packets; // Array von Zeigern auf Pakete
    int read;       // Lese-Position (retrieve_packet())
    int write;      // Schreib-Position (store_packet())
    long lost;      // Anzahl aller verlorenen Pakete
};


struct queue_t *queue_create(char *name, int size) {
    int i;
    struct queue_t *q;           /* temporaerer zeiger auf Queue */

    q = malloc (sizeof(struct queue_t));        //dynamisch

    if (q == NULL) {
        printf("Memory allocation failed");
        return 0;
    }

    q -> name = name;
    q -> size = size;
    q -> entries = 0;
    q -> write   = 0;
    q -> read    = 0;
    q -> lost    = 0;

    return (q);
}


long queue_store(struct queue_t * q, struct packet_t * p) {

    int total = 0;
    p -> name = q -> name;


    if (q -> entries < q -> size) {

        q -> entries++;
        q -> write++;

        total ++;

        if (q -> write > q -> size) {
            q -> write = 0;
        }

        return total;
    }

    else {
        packet_destroy(p);
        q -> lost ++;
        return 0;
}
}


struct packet_t* queue_retrieve(struct queue_t *q) {


    struct packet_t *p;
    p = malloc (sizeof(struct packet_t));
    struct packet_t *queue = NULL;

    if (q -> entries > 0) {
    q -> read ++;
    q -> entries --;
    packet_destroy(p);

        if (q -> read > q -> size ) {
            q -> read = 0;
        }
    }

    return (p);
}

int queue_destroy(struct queue_t *q) {

    free(q);

}

struct packet_t* packet_create(char *p) {
    struct packet_t * packet;
    packet = malloc (sizeof(struct packet_t));

    packet -> name = p;

    return (packet);
}


int packet_destroy(struct packet_t *packet) {

    free(packet);
    return 0;
}






int main(void) {

    long i;

    struct queue_t *Q;                              // Zeiger auf Warteschlange
    struct packet_t *P;                             // Zeiger auf Paket

    clock_t start, ende;

    start = clock();

    for (i = 0; i < 1000000; i++) {
        P = packet_create ("tester");
    }
    ende = clock();
    printf("Pakete erzeugen:\n");
    printf("i     = %ld\n", i);
    printf("T[s]  = %g\n", (double) (ende - start) / CLOCKS_PER_SEC);
    printf("\n");


    start = clock();
    for (i = 0; i < 1000000; i++) {
        Q = queue_create ("test-queue mit 100 Plaetzen", 100);
    }
    ende = clock();

    printf("Queues erzeugen:\n");
    printf("i     =%ld\n", i);
    printf("T[s]  = %g\n", (double) (ende - start) / CLOCKS_PER_SEC);
    printf("\n");




    start = clock();

    Q = queue_create ("test, 100", 100);

    // Queue halb fuellen
    for (i = 0; i < 50; i++) {
        P = packet_create ("nix");
        queue_store (Q,P);
    }

    // viele Pakete erzeugen
    for (i = 0; i < 1000000; i++) {
        P = packet_create ("nix");
        queue_store (Q,P);
        P=queue_retrieve(Q);
        packet_destroy(P);
    }

    // Vorbefuellung entfernen
    for (i = 0; i < 50; i++) {
        P=queue_retrieve(Q);
        packet_destroy(P);
    }


    ende = clock();

    printf("Queue erzeugen, <Paket erzeugen, speichern,laden,zerstoeren>:\n");

    printf("i     =%ld\n", i);
    printf("T[s]  = %g\n", (double) (ende - start) / CLOCKS_PER_SEC);
    printf("\n");




    start = clock();

    Q = queue_create ("test-queue fuer 1000 Pakete", 1000);

    for (i = 0; i < 900; i++) {
        P = packet_create ("aha");
        queue_store (Q,P);

    }
    for (i = 0; i < 901; i++) {
        P=queue_retrieve(Q);
        if (NULL == P)
            printf ("kein Paket\n");
        else
            packet_destroy(P);

    }
    ende = clock();

    printf("Queue erzeugen, <Paket erzeugen, speichern,lasden,zerstoeren>:\n");

    printf("i     =%ld\n", i);
    printf("T[s]  = %g\n", (double) (ende - start) / CLOCKS_PER_SEC);
    printf("\n");


    start = clock();

    Q = queue_create ("test, 1000", 1000);

    for (i = 0; i < 900; i++) {
        P = packet_create ((int)i,0.0,0L,NULL);
        queue_store (Q,P);

    }
    for (i = 0; i < 450; i++) {
        P=queue_retrieve(Q);
        if (NULL == P)
            printf ("kein Paket\n");
        else
            packet_destroy(P);

    }
    ende = clock();

    printf("Queue erzeugen, <Paket erzeugen, speichern,laden,zerstoeren>:\n");

    printf("i     =%ld\n", i);
    printf ("Q->entries = %d\n", Q->entries);
    printf("T[s]  = %g\n", (double) (ende - start) / CLOCKS_PER_SEC);
    printf("\n");
}
Stockmanns
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1 Answers1

1

The error means that you attempt to use the function packet_destroy before you define it, so the compiler doesn't know how the function should be called.

You can fix this by either moving packet_destroy before any function that uses it, or by adding a declaration of the function before you use it.

dbush
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