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DEFINITIONS
This source file includes following functions.
- umsdos_manglename
- umsdos_evalrecsize
- umsdos_evalrecsize_old
- umsdos_parse
- main
/*
* 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)
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{
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)
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{
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)
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{
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 (
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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",
#else
/*
* 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[])
/* [<][>][^][v][top][bottom][index][help] */
{
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