/*
 * Author: Matt Dillon, placed in the public domain.
 *
 * zoneread device blksize(K) numzones seek-dispersion(M) mode
 */
#include <sys/types.h>
#include <sys/fcntl.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <sys/wait.h>
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>

int
main(int ac, char **av)
{
    int i;
    int fd;
    int bs;
    int numzones;
    off_t seekdisp;
    off_t seekbase;
    off_t count;
    int mode;
    char *buf;

    if (ac != 6) {
	fprintf(stderr, "zoneread device blksize(K) numzones "
			"seek-dispersion(M) mode\n");
	fprintf(stderr, "mode 1 - linear fwd reads from each zone\n"
			"mode 2 - linear rev reads from each zone\n"
			"mode 3 - linear fwd skip interleave x 1\n"
			"mode 4 - linear fwd skip interleave x 2\n"
			"mode 5 - no seeking within the zone\n"
	);
	exit(1);
    }
    fd = open(av[1], O_RDONLY);
    if (fd < 0) {
	perror("open");
	exit(1);
    }
    bs = strtol(av[2], NULL, 0);
    numzones = strtol(av[3], NULL, 0);
    seekdisp = strtoll(av[4], NULL, 0);
    mode = strtol(av[5], NULL, 0);
    bs *= 1024;
    seekdisp *= 1024 * 1024;

    buf = mmap(NULL, bs, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0);
    printf("device %s bs=%d numzones=%d seekdisp=%lld mode=%d",
	    av[1], bs, numzones, (long long)seekdisp, mode);
    switch(mode) {
    case 1:
	printf("(linear fwd read)\n");
	break;
    case 2:
	printf("(linear rev read)\n");
	break;
    case 3:
	printf("(linear fwd skip interleave x 1)\n");
	break;
    case 4:
	printf("(linear fwd skip interleave x 2)\n");
	break;
    default:
	printf("(no seeking within zone)\n");
	break;
    }

    for (i = 0; i < numzones; ++i) {
	if (fork() == 0) {
	    for (;;) {
		for (count = 0; count < seekdisp; count += bs) {
		    switch(mode) {
		    case 1:
			seekbase = seekdisp * i + count;
			break;
		    case 2:
			seekbase = seekdisp * i + (seekdisp - count);
			break;
		    case 3:
			seekbase = seekdisp * i + count;
			if ((count / bs) & 1)
			    seekbase -= bs;
			else
			    seekbase += bs;
			break;
		    case 4:
			seekbase = seekdisp * i + count;
			switch((count / bs) & 3) {
			case 0:
			    seekbase += bs * 3;
			    break;
			case 1:
			    seekbase += bs * 2;
			    break;
			case 2:
			    seekbase -= bs * 2;
			    break;
			case 3:
			    seekbase -= bs * 3;
			    break;
			}
			break;
		    default:
			seekbase = seekdisp * i;
			break;
		    }
		    lseek(fd, seekbase, 0);
		    read(fd, buf, bs);
		}
	    }
	    /* not reached */
	}
    }
    while (waitpid(-1, NULL, 0) > 0)
	;
    exit(0);
}