Linux 2.2.0

[davej-history.git] / fs / umsdos / mangle.c

/*
 *  linux/fs/umsdos/mangle.c
 *
 *      Written 1993 by Jacques Gelinas 
 *
 * Control the mangling of file name to fit msdos name space.
 * Many optimisations by GLU == dglaude@is1.vub.ac.be (Glaude David)
 */

#include <linux/errno.h>
#include <linux/string.h>
#include <linux/kernel.h>
#include <linux/umsdos_fs.h>

/* (This file is used outside of the kernel) */
#ifndef __KERNEL__
#define KERN_WARNING
#endif

/*
 * Complete the mangling of the MSDOS fake name
 * based on the position of the entry in the EMD file.
 * 
 * Simply complete the job of umsdos_parse; fill the extension.
 * 
 * Beware that info->f_pos must be set.
 */
void umsdos_manglename (struct umsdos_info *info)
{
        if (info->msdos_reject) {
                /* #Specification: file name / non MSDOS conforming / mangling
                 * Each non MSDOS conforming file has a special extension
                 * build from the entry position in the EMD file.
                 * 
                 * This number is then transform in a base 32 number, where
                 * each digit is expressed like hexadecimal number, using
                 * digit and letter, except it uses 22 letters from 'a' to 'v'.
                 * The number 32 comes from 2**5. It is faster to split a binary
                 * number using a base which is a power of two. And I was 32
                 * when I started this project. Pick your answer :-) .
                 * 
                 * If the result is '0', it is replace with '_', simply
                 * to make it odd.
                 * 
                 * This is true for the first two character of the extension.
                 * The last one is taken from a list of odd character, which
                 * are:
                 * 
                 * { } ( ) ! ` ^ & @
                 * 
                 * With this scheme, we can produce 9216 ( 9* 32 * 32)
                 * different extensions which should not clash with any useful
                 * extension already popular or meaningful. Since most directory
                 * have much less than 32 * 32 files in it, the first character
                 * of the extension of any mangled name will be {.
                 * 
                 * Here are the reason to do this (this kind of mangling).
                 * 
                 * -The mangling is deterministic. Just by the extension, we
                 * are able to locate the entry in the EMD file.
                 * 
                 * -By keeping to beginning of the file name almost unchanged,
                 * we are helping the MSDOS user.
                 * 
                 * -The mangling produces names not too ugly, so an msdos user
                 * may live with it (remember it, type it, etc...).
                 * 
                 * -The mangling produces names ugly enough so no one will
                 * ever think of using such a name in real life. This is not
                 * fool proof. I don't think there is a total solution to this.
                 */
                int entry_num;
                char *pt = info->fake.fname + info->fake.len;
                /* lookup for encoding the last character of the extension 
                 * It contains valid character after the ugly one to make sure 
                 * even if someone overflows the 32 * 32 * 9 limit, it still 
                 * does something 
                 */
#define SPECIAL_MANGLING '{','}','(',')','!','`','^','&','@'
                static char lookup3[] =
                {
                        SPECIAL_MANGLING,
                /* This is the start of lookup12 */
                        '_', '1', '2', '3', '4', '5', '6', '7', '8', '9',
                        'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o',
                        'p', 'q', 'r', 's', 't', 'u', 'v'
                };

#define lookup12 (lookup3+9)
                entry_num = info->f_pos / UMSDOS_REC_SIZE;
                if (entry_num > (9* 32 * 32)){
                        printk (KERN_WARNING "UMSDOS: more than 9216 files in a directory.\n"
                                "This may break the mangling strategy.\n"
                                "Not a killer problem. See doc.\n");
                }
                *pt++ = '.';
                *pt++ = lookup3 [(entry_num >> 10) & 31];
                *pt++ = lookup12[(entry_num >> 5) & 31];
                *pt++ = lookup12[entry_num & 31];
                *pt = '\0';             /* help doing printk */ 
                info->fake.len += 4;
                info->msdos_reject = 0;         /* Avoid mangling twice */
        }
}

/*
 * Evaluate the record size needed to store of name of len character.
 * The value returned is a multiple of UMSDOS_REC_SIZE.
 */
int umsdos_evalrecsize (int len)
{
        struct umsdos_dirent dirent;
        int nbrec = 1 + ((len - 1 + (dirent.name - (char *) &dirent))
                         / UMSDOS_REC_SIZE);

        return nbrec * UMSDOS_REC_SIZE;
        /*
         * GLU        This should be inlined or something to speed it up to the max.
         * GLU        nbrec is absolutely not needed to return the value.
         */
}
#ifdef TEST
int umsdos_evalrecsize_old (int len)
{
        struct umsdos_dirent dirent;
        int size = len + (dirent.name - (char *) &dirent);
        int nbrec = size / UMSDOS_REC_SIZE;
        int extra = size % UMSDOS_REC_SIZE;

        if (extra > 0)
                nbrec++;
        return nbrec * UMSDOS_REC_SIZE;
}
#endif


/*
 * Fill the struct info with the full and msdos name of a file
 * Return 0 if all is OK, a negative error code otherwise.
 */
int umsdos_parse (
                         const char *fname,
                         int len,
                         struct umsdos_info *info)
{
        int ret = -ENAMETOOLONG;

        /* #Specification: file name / too long
         * If a file name exceed UMSDOS maxima, the file name is silently
         * truncated. This makes it conformant with the other file system
         * of Linux (minix and ext2 at least).
         */
        if (len > UMSDOS_MAXNAME)
                len = UMSDOS_MAXNAME;
        {
                const char *firstpt = NULL;     /* First place we saw a "." in fname */

                /* #Specification: file name / non MSDOS conforming / base length 0
                 * file names beginning with a period '.' are invalid for MS-DOS.
                 * It needs absolutely a base name. So the file name is mangled
                 */
                int ivldchar = fname[0] == '.';         /* At least one invalid character */
                int msdos_len = len;
                int base_len;

                /*
                 * cardinal_per_size tells if there exists at least one
                 * DOS pseudo device on length n.  See the test below.
                 */
                static const char cardinal_per_size[9] =
                {
                        0, 0, 0, 1, 1, 0, 1, 0, 1
                };

                /*
                 * lkp translate all character to acceptable character (for DOS).
                 * When lkp[n] == n, it means also it is an acceptable one.
                 * So it serves both as a flag and as a translator.
                 */
                static char lkp[256];
                static char is_init = 0;

                if (!is_init) {
                        /*
                         * Initialisation of the array is easier and less error
                         * prone like this.
                         */
                        int i;
                        static const char *spc = "\"*+,/:;<=>?[\\]|~";

                        is_init = 1;
                        for (i = 0; i <= 32; i++)
                                lkp[i] = '#';
                        for (i = 33; i < 'A'; i++)
                                lkp[i] = (char) i;
                        for (i = 'A'; i <= 'Z'; i++)
                                lkp[i] = (char) (i + ('a' - 'A'));
                        for (i = 'Z' + 1; i < 127; i++)
                                lkp[i] = (char) i;
                        for (i = 128; i < 256; i++)
                                lkp[i] = '#';

                        lkp['.'] = '_';
                        while (*spc != '\0')
                                lkp[(unsigned char) (*spc++)] = '#';
                }
                /*  GLU
                 * File names longer than 8+'.'+3 are invalid for MS-DOS,
                 * so the file name is to be mangled--no further test is needed.
                 * This speeds up handling of long names.
                 * The position of the last point is no more necessary anyway.
                 */
                if (len <= (8 + 1 + 3)) {
                        const char *pt = fname;
                        const char *endpt = fname + len;

                        while (pt < endpt) {
                                if (*pt == '.') {
                                        if (firstpt != NULL) {
                                                /* 2 . in a file name. Reject */
                                                ivldchar = 1;
                                                break;
                                        } else {
                                                int extlen = (int) (endpt - pt);

                                                firstpt = pt;
                                                if (firstpt - fname > 8) {
                                                        /* base name longer than 8: reject */
                                                        ivldchar = 1;
                                                        break;
                                                } else if (extlen > 4) {
                                                        /* Extension longer than 4 (including .): reject */
                                                        ivldchar = 1;
                                                        break;
                                                } else if (extlen == 1) {
                                                        /* #Specification: file name / non MSDOS conforming / last char == .
                                                         * If the last character of a file name is
                                                         * a period, mangling is applied. MS-DOS does
                                                         * not support those file names.
                                                         */
                                                        ivldchar = 1;
                                                        break;
                                                } else if (extlen == 4) {
                                                        /* #Specification: file name / non MSDOS conforming / mangling clash
                                                         * To avoid clash with    the umsdos mangling, any file
                                                         * with a special character as the first character
                                                         * of the extension will be mangled. This solves the
                                                         * following problem:
                                                         * 
                                                         * #
                                                         * touch FILE
                                                         * # FILE is invalid for DOS, so mangling is applied
                                                         * # file.{_1 is created in the DOS directory
                                                         * touch file.{_1
                                                         * # To UMSDOS file point to a single DOS entry.
                                                         * # So file.{_1 has to be mangled.
                                                         * #
                                                         */
                                                        static char special[] =
                                                        {
                                                                SPECIAL_MANGLING, '\0'
                                                        };

                                                        if (strchr (special, firstpt[1]) != NULL) {
                                                                ivldchar = 1;
                                                                break;
                                                        }
                                                }
                                        }
                                } else if (lkp[(unsigned char) (*pt)] != *pt) {
                                        ivldchar = 1;
                                        break;
                                }
                                pt++;
                        }
                } else {
                        ivldchar = 1;
                }
                if (ivldchar
                    || (firstpt == NULL && len > 8)
                    || (len == UMSDOS_EMD_NAMELEN
                        && memcmp (fname, UMSDOS_EMD_FILE, UMSDOS_EMD_NAMELEN) == 0)) {
                        /* #Specification: file name / --linux-.---
                         * The name of the EMD file --linux-.--- is map to a mangled
                         * name. So UMSDOS does not restrict its use.
                         */
                        /* #Specification: file name / non MSDOS conforming / mangling
                         * Non MSDOS conforming file names must use some alias to fit
                         * in the MSDOS name space.
                         * 
                         * The strategy is simple. The name is simply truncated to
                         * 8 char. points are replace with underscore and a
                         * number is given as an extension. This number correspond
                         * to the entry number in the EMD file. The EMD file
                         * only need to carry the real name.
                         * 
                         * Upper case is also converted to lower case.
                         * Control character are converted to #.
                         * Spaces are converted to #.
                         * The following characters are also converted to #.
                         * #
                         * " * + , / : ; < = > ? [ \ ] | ~
                         * #
                         * 
                         * Sometimes the problem is not in MS-DOS itself but in
                         * command.com.
                         */
                        int i;
                        char *pt = info->fake.fname;

                        base_len = msdos_len = (msdos_len > 8) ? 8 : msdos_len;
                        /*
                         * There is no '.' any more so we know for a fact that
                         * the base length is the length.
                         */
                        memcpy (info->fake.fname, fname, msdos_len);
                        for (i = 0; i < msdos_len; i++, pt++)
                                *pt = lkp[(unsigned char) (*pt)];
                        *pt = '\0';     /* GLU  We force null termination. */
                        info->msdos_reject = 1;
                        /*
                         * The numeric extension is added only when we know
                         * the position in the EMD file, in umsdos_newentry(),
                         * umsdos_delentry(), and umsdos_findentry().
                         * See umsdos_manglename().
                         */
                } else {
                        /* Conforming MSDOS file name */
                        strncpy (info->fake.fname, fname, len);
                        info->msdos_reject = 0;
                        base_len = firstpt != NULL ? (int) (firstpt - fname) : len;
                }
                if (cardinal_per_size[base_len]) {
                        /* #Specification: file name / MSDOS devices / mangling
                         * To avoid unreachable file from MS-DOS, any MS-DOS conforming
                         * file with a basename equal to one of the MS-DOS pseudo
                         * devices will be mangled.
                         * 
                         * If a file such as "prn" was created, it would be unreachable
                         * under MS-DOS because "prn" is assumed to be the printer, even
                         * if the file does have an extension.
                         * 
                         * Since the extension is unimportant to MS-DOS, we must patch
                         * the basename also. We simply insert a minus '-'. To avoid
                         * conflict with valid file with a minus in front (such as
                         * "-prn"), we add an mangled extension like any other
                         * mangled file name.
                         * 
                         * Here is the list of DOS pseudo devices:
                         * 
                         * #
                         * "prn","con","aux","nul",
                         * "lpt1","lpt2","lpt3","lpt4",
                         * "com1","com2","com3","com4",
                         * "clock$"
                         * #
                         * 
                         * and some standard ones for common DOS programs
                         * 
                         * "emmxxxx0","xmsxxxx0","setverxx"
                         * 
                         * (Thanks to Chris Hall <cah17@phoenix.cambridge.ac.uk>
                         * for pointing these out to me).
                         * 
                         * Is there one missing?
                         */
                        /* This table must be ordered by length */
                        static const char *tbdev[] =
                        {
                                "prn", "con", "aux", "nul",
                                "lpt1", "lpt2", "lpt3", "lpt4",
                                "com1", "com2", "com3", "com4",
                                "clock$",
                                "emmxxxx0", "xmsxxxx0", "setverxx"
                        };

                        /* Tell where to find in tbdev[], the first name of */
                        /* a certain length */
                        static const char start_ind_dev[9] =
                        {
                                0, 0, 0, 4, 12, 12, 13, 13, 16
                        };
                        char basen[9];
                        int i;

                        for (i = start_ind_dev[base_len - 1]; i < start_ind_dev[base_len]; i++) {
                                if (memcmp (info->fake.fname, tbdev[i], base_len) == 0) {
                                        memcpy (basen, info->fake.fname, base_len);
                                        basen[base_len] = '\0';         /* GLU  We force null termination. */
                                        /*
                                         * GLU        We do that only if necessary; we try to do the
                                         * GLU        simple thing in the usual circumstance. 
                                         */
                                        info->fake.fname[0] = '-';
                                        strcpy (info->fake.fname + 1, basen);   /* GLU  We already guaranteed a null would be at the end. */
                                        msdos_len = (base_len == 8) ? 8 : base_len + 1;
                                        info->msdos_reject = 1;
                                        break;
                                }
                        }
                }
                info->fake.fname[msdos_len] = '\0';     /* Help doing printk */
                /* GLU      This zero should (always?) be there already. */
                info->fake.len = msdos_len;
                /* Why not use info->fake.len everywhere? Is it longer?
                 */
                memcpy (info->entry.name, fname, len);
                info->entry.name[len] = '\0';   /* for printk */
                info->entry.name_len = len;
                ret = 0;
        }
        /*
         * Evaluate how many records are needed to store this entry.
         */
        info->recsize = umsdos_evalrecsize (len);
        return ret;
}

#ifdef TEST

struct MANG_TEST {
        char *fname;            /* Name to validate */
        int msdos_reject;       /* Expected msdos_reject flag */
        char *msname;           /* Expected msdos name */
};

struct MANG_TEST tb[] =
{
        "hello", 0, "hello",
        "hello.1", 0, "hello.1",
        "hello.1_", 0, "hello.1_",
        "prm", 0, "prm",

#ifdef PROPOSITION
        "HELLO", 1, "hello",
        "Hello.1", 1, "hello.1",
        "Hello.c", 1, "hello.c",
#elseif
/*
 * I find the three examples below very unfortunate.  I propose to
 * convert them to lower case in a quick preliminary pass, then test
 * whether there are other troublesome characters.  I have not made
 * this change, because it is not easy, but I wanted to mention the 
 * principle.  Obviously something like that would increase the chance
 * of collisions, for example between "HELLO" and "Hello", but these
 * can be treated elsewhere along with the other collisions.
 */

        "HELLO", 1, "hello",
        "Hello.1", 1, "hello_1",
        "Hello.c", 1, "hello_c",
#endif

        "hello.{_1", 1, "hello_{_",
        "hello\t", 1, "hello#",
        "hello.1.1", 1, "hello_1_",
        "hel,lo", 1, "hel#lo",
        "Salut.Tu.vas.bien?", 1, "salut_tu",
        ".profile", 1, "_profile",
        ".xv", 1, "_xv",
        "toto.", 1, "toto_",
        "clock$.x", 1, "-clock$",
        "emmxxxx0", 1, "-emmxxxx",
        "emmxxxx0.abcd", 1, "-emmxxxx",
        "aux", 1, "-aux",
        "prn", 1, "-prn",
        "prn.abc", 1, "-prn",
        "PRN", 1, "-prn",
  /* 
   * GLU        WARNING:  the results of these are different with my version
   * GLU        of mangling compared to the original one.
   * GLU        CAUSE:  the manner of calculating the baselen variable.
   * GLU                For you they are always 3.
   * GLU                For me they are respectively 7, 8, and 8.

   */
        "PRN.abc", 1, "prn_abc",
        "Prn.abcd", 1, "prn_abcd",
        "prn.abcd", 1, "prn_abcd",
        "Prn.abcdefghij", 1, "prn_abcd"
};

int main (int argc, char *argv[])
{
        int i, rold, rnew;

        printf ("Testing the umsdos_parse.\n");
        for (i = 0; i < sizeof (tb) / sizeof (tb[0]); i++) {
                struct MANG_TEST *pttb = tb + i;
                struct umsdos_info info;
                int ok = umsdos_parse (pttb->fname, strlen (pttb->fname), &info);

                if (strcmp (info.fake.fname, pttb->msname) != 0) {
                        printf ("**** %s -> ", pttb->fname);
                        printf ("%s <> %s\n", info.fake.fname, pttb->msname);
                } else if (info.msdos_reject != pttb->msdos_reject) {
                        printf ("**** %s -> %s ", pttb->fname, pttb->msname);
                        printf ("%d <> %d\n", info.msdos_reject, pttb->msdos_reject);
                } else {
                        printf ("     %s -> %s %d\n", pttb->fname, pttb->msname
                                ,pttb->msdos_reject);
                }
        }
        printf ("Testing the new umsdos_evalrecsize.");
        for (i = 0; i < UMSDOS_MAXNAME; i++) {
                rnew = umsdos_evalrecsize (i);
                rold = umsdos_evalrecsize_old (i);
                if (!(i % UMSDOS_REC_SIZE)) {
                        printf ("\n%d:\t", i);
                }
                if (rnew != rold) {
                        printf ("**** %d newres: %d != %d \n", i, rnew, rold);
                } else {
                        printf (".");
                }
        }
        printf ("\nEnd of Testing.\n");

        return 0;
}

#endif