/* gcc -Wall lio_listio.c -lrt
* 
* Written for testing lio_listio() performance while demultiplexing a huge stream-file,
* eg. during recovery of a crashed server: extract 1 transaction log out of, say 32 multiplexed logstreams
*
* example performance for block-aligned data: FEILSIZE=1369084021 (bytes)
* time /tmp/lio_listio 
* real    0m23.075s
* travelspeed = 1369084021 / 23 =  5.95e+07
* extractspeed = travelspeed / (STEPSIZE/BUFSIZE) =  1.86e+06  5-10 MByte would be nicer 
(the 1 tera SATA disk - no raid - can do 40+Mbyte in streaming mode).
* Actual extractspeed will be even worse, since this was on 4kbyte block boundary.
* Example performance for non-block-aligned data (and 5000 byte chunks, which is rather suboptimal):
FILESIZE = 1937838067
TIME=33.803
TRAVELSPEED=FILESIZE/TIME
TRAVELSPEED =  5.7327e+07
extractspeed=TRAVELSPEED/40
extractspeed =  1.4332e+06

*/

#include <aio.h>
#include <stdio.h>
#include <stdlib.h>
#include <strings.h>

#define BUFSIZE 5000
#define MBUFSIZE (BUFSIZE+8)

#define STEPSIZE (200001)
#define FILESIZE 1937838067
#define MAX_LIST ((int)(FILESIZE/STEPSIZE))

struct aiocb aiocbs[MAX_LIST];
struct aiocb *list[MAX_LIST];
int fd, ret;
char *bigbuf; /* will be [MBUFSIZE * MAX_LIST]; */

int main(int argc, char** argv)
{
	int i;
	/* ln -s yourHUGEfile.avi bigfile.dat and #define MAX_LIST filesize / STEPSIZE  */
  fd = open( "bigfile.dat", O_RDONLY );
  if (fd < 0) perror("open");

  /* Zero out the aiocb structure (recommended) */
	bzero( (char *)aiocbs, MAX_LIST * sizeof(struct aiocb) );
	bzero( (char *)list, sizeof(list) ); // overwritten inside the for below:

if(NULL == (bigbuf = malloc( MBUFSIZE * MAX_LIST )))  perror("malloc"); ;

/* Prepare the first aiocb */
for (i=0; i<MAX_LIST; i++){
	struct aiocb *ap = &aiocbs[i];
	list[i] = ap;
	ap->aio_fildes = fd;
	// if(NULL == (ap->aio_buf = malloc( (BUFSIZE & ~7) + 8)))  perror("malloc");
	ap->aio_buf = &bigbuf[i * MBUFSIZE];
	ap->aio_nbytes = BUFSIZE;
	ap->aio_offset = i*STEPSIZE; // next_offset;
	ap->aio_lio_opcode = LIO_READ;
}

ret = lio_listio( LIO_WAIT, list, MAX_LIST, NULL );
if (ret < 0) perror("lio_listio");


/* while ( aio_error( &my_aiocb ) == EINPROGRESS ) ;
*
*  if ((ret = aio_return( &my_iocb )) > 0) {
* got ret bytes on the read
* } else {
* read failed, consult errno
* }
*/

return 0;
}