/*      $OpenBSD: shortseek.c,v 1.1 2013/11/03 00:20:24 schwarze Exp $  */

/*      Written by Otto Moerbeek, 2006,  Public domain. */
/*      Modified by Ingo Schwarze, 2013,  Public domain. */

#include <sys/types.h>
#include <dirent.h>
#include <err.h>
#include <limits.h>
#include <stdio.h>
#include <string.h>

#include "utils.h"

#define NFILES 5

static void
shortloop(DIR *dp, int iend, int iback)
{
        struct dirent *f;
        char fend[PATH_MAX], fback[PATH_MAX];
        long pos, t, remember = -1;
        int i;

        rewinddir(dp);
        snprintf(fend, sizeof fend, "%d", iend);
        snprintf(fback, sizeof fback, "%d", iback);

        /* Scan to iend, remember where iback is. */

        for (;;) {
                pos = telldir(dp);
                f = readdir(dp);
                if (f == NULL)
                        errx(1, "file %s not found", fend);
                if (strcmp(fback, f->d_name) == 0)
                        remember = pos;
                if (strcmp(fend, f->d_name) == 0)
                        break;
        }
        if (remember == -1)
                errx(1, "file %s not found", fback);

        /* Go back to iback, checking seekdir, telldir and readdir. */

        seekdir(dp, remember);
        if ((t = telldir(dp)) != remember)
                errx(1, "tell after seek %s %ld != %ld", fback, t, remember);
        if ((t = telldir(dp)) != remember)
                errx(1, "tell after tell %s %ld != %ld", fback, t, remember);
        f = readdir(dp);
        if (f == NULL)
                errx(1, "readdir %s at %ld", fback, remember);

        if (strcmp(f->d_name, fback))
                errx(1, "name mismatch: %s != %s", f->d_name, fback);

        /* Check that readdir can iterate the remaining files. */

        for (i = iback + 1; i < NFILES; i++) {
                f = readdir(dp);
                if (f == NULL)
                        errx(1, "readdir %i failed", i);
        }

        /* Check that readdir stops at the right place. */

        f = readdir(dp);
        if (f != NULL)
                errx(1, "readdir %i returned %s", NFILES, f->d_name);
}

void
shortseek(void)
{
        DIR *dp;
        int iend, iback;

        createfiles(NFILES);

        dp = opendir("d");
        if (dp == NULL)
                err(1, "shortseek: opendir");

        for (iend = 0; iend < NFILES; iend++)
                for (iback = 0; iback <= iend; iback++)
                        shortloop(dp, iend, iback);

        closedir(dp);
        delfiles();
}