Fill file ASCII values

Question

I want to create a file filled with 0 or other letters. Here's my function

int fill(const int d, struct aiocb *aiorp, void *buf, const int count){
        int rv = 0;
        memset( (void *)aiorp, 0, sizeof( struct aiocb ) ); // <-here second paramether is 0
        aiorp->aio_fildes = d;
        aiorp->aio_buf = buf;
        aiorp->aio_nbytes = count;
        aiorp->aio_offset = 0;
        rv = aio_write( aiorp );
        return rv;
}

Here's my main

int main(int argc, char * argv[]){
        int des;
        int rv;
        struct aiocb aior;
        char buffer[1000];
        if(argc == 3){
                printf("just %s\n", argv[1]);
                des = createFile(argv[1]);
                rv = fill(des, &aior, buffer, sizeof(buffer));
        }
        return 0;
}

So my output should be file filled with zero values, but my fle is filled with garbage

^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@$
y▒^X^@^@^@^@^@^@^@
s|▒^@^@^@^@^@^@^@^@^@^@^@^@▒r|▒^@^@^@^@▒▒^?▒(▒▒▒▒▒{▒▒
y▒^P^@^@^@▒
y▒^A^@^@^@d^Cy▒^@^@^@^@▒
y▒^T
y▒^P▒▒▒^@^@^@^@^@^@^@^
...

Why? What's wrong?

Here's the code :

sukurti - create new file if that file don't exist and fill - fill created file

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <aio.h>
#define MB 1024

int sukurti(char *name);
int fill(const int d, struct aiocb *aiorp, void *buf, const int count);

int sukurti(char *name){
   int dskr;
   dskr = open( name, O_RDONLY );
   if( dskr == -1 ){
          printf("Failas sukurtas, nes jo nebuvo\n");
          dskr = open( name, O_WRONLY | O_CREAT, 0644);

   }else{
           printf("Jau yra toks failas!\n");
           exit(1);
   }
   return dskr;
}

int fill(const int d, struct aiocb *aiorp, void *buf, const int count){
        int rv = 0;
        memset( (void *)aiorp, 'A', sizeof( struct aiocb ) );
        aiorp->aio_fildes = d;
        aiorp->aio_buf = buf;
        aiorp->aio_nbytes = count;
        aiorp->aio_offset = 0;
        rv = aio_write( aiorp );
        return rv;

}

int main(int argc, char * argv[]){
        int des;
        int rv;
        struct aiocb aior;
        int x = atoi(argv[2]);
        printf("%d\n", x);
        int size = MB * MB * x;
        char buffer[size];
        if(argc == 3){
                printf("just %s\n", argv[1]);
                des = sukurti(argv[1]);
                rv = fill(des, &aior, buffer, sizeof(buffer));
        }else{
                printf("Blogas\n");
        }
        return 0;
}

EDIT: I know that my writting to file ends

Answer 1

Three ssues here:

1. buffer is not initalised. Do this using

   memset(buffer, 
     <what ever 8bit value you want the file to be filled with>, 
     sizeof buffer);
   

   right after defining it in main().

2. aior is initialise wrongly. Initialise it to all 0 using

   memset(aiorb, 0, sizeof aior);
   

   right after defining it in main() and remove the call to memset() in fill().

3. Finally the program most likely ends before the buffer had been asynchronously written to disk.

   To fix this define a notification method as mentioned under man 7 aio. And make the program wait for this notification to be received before ending the program.

   This for example can be done by asking for completion notification via signal and wait for this signal.

   To do so modify your code as follows:

   • Add the following two lines to the intialisation of what aiorp is pointing to in fill():

     aiorp->aio_sigevent.sigev_notify = SIGEV_SIGNAL;
     aiorp->aio_sigevent.sigev_signo = SIGUSR1;
     

   • To be able to handle the notifying signal sent (without ending the program) a signal handler needs to be setup:

     void handler(int sig)
     {
       /* Do nothing. */
     }
     

   • Install this handler by calling

     signal(handler, SIGUSR1);
     

     right at the beginning of the program.

   • Before returning from main() call wait_for_completion(SIGUSR1) which might look like this:

     void wait_for_completion(int sig)
     {
       sigset_t set;
       sigemptyset(&set);
       sigaddset(&set, sig);
     
       sigwait(&set, &sig); /* This blocks until sig had 
                               been received by the program. */
       printf("Completion notification for asynchronous 'write'-operation received.\n");
     }  
     

   ^{Add error handling as appropriate. I left it out for the sake of readability.}

Answer 2

  memset( (void *)aiorp, '0', sizeof( struct aiocb ) );

0 is not '0', you need to actually use the ASCII value (48 if i recall correctly.)