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    SubjectRe: Filesize limitation
    Andre Uratsuka Manoel <> writes:

    > Hello gentlemen,
    > I was contact by people asking about filesize limits in Linux as
    > they tried to create a 2GB file, but couldn't. I figured the problem
    > might be the filesize limitation. At least that is what I'd expect to
    > happen with a file that size. Am I right on that? If it is so, is there
    > a 64-bit filesystem for Linux?

    There is a very simple workaround for this. Linux allows partitions much
    bigger than 2GB. So just use multiple files:

    /* Only supports one big file, extending it for more is trivial */
    /* Untested and no error checking. */
    /* IO is limited to 2^31 bytes (that's OK because i386 linux only
    * has a address room of 2^30 bytes per process) */
    typedef long long big_offset_t;

    int bigfdtab[NROPEN];
    big_offset_t big_offset;
    char *big_name;
    int big_mode;

    #define BIGFD(offset) (bigfdtab[(offset) >> 31])
    #define BIGOFFSET(offset) ((offset) & 0x7fffffff)

    static int bopen(int fd)
    char name[strlen(big_name) + 10];
    sprintf(name, "%s%d", fd);
    bigfdtab[fd] = open(name, big_flags, big_mode);

    /* Use return value only for error checking */
    int big_open(char *name, int flags, int mode)
    big_name = strdup(name);
    big_flags = flags;
    big_offset = 0;
    big_mode = mode;
    return bopen(0);

    void big_close()
    int n;
    for (n = 2; n < NROPEN; n++)
    if (bigfdtab[n])
    free(big_name); big_name = NULL;

    int big_read(char *buf, long size)
    int fd = BIGFD(big_offset);
    long r;

    if (!bigfdtab[fd]) {
    fd = bigfdtab[fd];

    if (BIGFD(bigoffset+size) != fd) {
    /* Crosses file borders */
    lseek(fd, BIGOFFSET(big_offset), SEEK_SET);
    r = read(fd, buf, (big_offset+size) & 0x7fffffff);
    big_offset += r;
    size -= r;
    fd = BIGFD(big_offset);

    /* Could be optimized. */
    lseek(fd, BIGOFFSET(big_offset), SEEK_SET);
    r = read(fd, buf, size);
    big_offset += r;
    return r;

    That's very simple of course and has a few problems (you can still overflow
    the fd table by using big holes, it does unnecessary seeks etc.) but you get
    the basic idea. I have never tried to compile it, so don't blame me if it
    doesn't :)


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      Last update: 2005-03-22 13:40    [W:0.028 / U:34.396 seconds]
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