[PATCH] hfs: NLS support

This adds NLS support to HFS.  Using the kernel options iocharset and codepage
it's possible to map the disk encoding to a local mapping.  If these options
are not used, it falls back to the old direct mapping.

Signed-off-by: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Roman Zippel 2005-09-06 15:18:49 -07:00 committed by Linus Torvalds
parent 717dd80e99
commit 328b922786
8 changed files with 176 additions and 46 deletions

View file

@ -20,12 +20,12 @@
* *
* Given the ID of the parent and the name build a search key. * Given the ID of the parent and the name build a search key.
*/ */
void hfs_cat_build_key(btree_key *key, u32 parent, struct qstr *name) void hfs_cat_build_key(struct super_block *sb, btree_key *key, u32 parent, struct qstr *name)
{ {
key->cat.reserved = 0; key->cat.reserved = 0;
key->cat.ParID = cpu_to_be32(parent); key->cat.ParID = cpu_to_be32(parent);
if (name) { if (name) {
hfs_triv2mac(&key->cat.CName, name); hfs_asc2mac(sb, &key->cat.CName, name);
key->key_len = 6 + key->cat.CName.len; key->key_len = 6 + key->cat.CName.len;
} else { } else {
memset(&key->cat.CName, 0, sizeof(struct hfs_name)); memset(&key->cat.CName, 0, sizeof(struct hfs_name));
@ -62,13 +62,14 @@ static int hfs_cat_build_record(hfs_cat_rec *rec, u32 cnid, struct inode *inode)
} }
} }
static int hfs_cat_build_thread(hfs_cat_rec *rec, int type, static int hfs_cat_build_thread(struct super_block *sb,
hfs_cat_rec *rec, int type,
u32 parentid, struct qstr *name) u32 parentid, struct qstr *name)
{ {
rec->type = type; rec->type = type;
memset(rec->thread.reserved, 0, sizeof(rec->thread.reserved)); memset(rec->thread.reserved, 0, sizeof(rec->thread.reserved));
rec->thread.ParID = cpu_to_be32(parentid); rec->thread.ParID = cpu_to_be32(parentid);
hfs_triv2mac(&rec->thread.CName, name); hfs_asc2mac(sb, &rec->thread.CName, name);
return sizeof(struct hfs_cat_thread); return sizeof(struct hfs_cat_thread);
} }
@ -93,8 +94,8 @@ int hfs_cat_create(u32 cnid, struct inode *dir, struct qstr *str, struct inode *
sb = dir->i_sb; sb = dir->i_sb;
hfs_find_init(HFS_SB(sb)->cat_tree, &fd); hfs_find_init(HFS_SB(sb)->cat_tree, &fd);
hfs_cat_build_key(fd.search_key, cnid, NULL); hfs_cat_build_key(sb, fd.search_key, cnid, NULL);
entry_size = hfs_cat_build_thread(&entry, S_ISDIR(inode->i_mode) ? entry_size = hfs_cat_build_thread(sb, &entry, S_ISDIR(inode->i_mode) ?
HFS_CDR_THD : HFS_CDR_FTH, HFS_CDR_THD : HFS_CDR_FTH,
dir->i_ino, str); dir->i_ino, str);
err = hfs_brec_find(&fd); err = hfs_brec_find(&fd);
@ -107,7 +108,7 @@ int hfs_cat_create(u32 cnid, struct inode *dir, struct qstr *str, struct inode *
if (err) if (err)
goto err2; goto err2;
hfs_cat_build_key(fd.search_key, dir->i_ino, str); hfs_cat_build_key(sb, fd.search_key, dir->i_ino, str);
entry_size = hfs_cat_build_record(&entry, cnid, inode); entry_size = hfs_cat_build_record(&entry, cnid, inode);
err = hfs_brec_find(&fd); err = hfs_brec_find(&fd);
if (err != -ENOENT) { if (err != -ENOENT) {
@ -127,7 +128,7 @@ int hfs_cat_create(u32 cnid, struct inode *dir, struct qstr *str, struct inode *
return 0; return 0;
err1: err1:
hfs_cat_build_key(fd.search_key, cnid, NULL); hfs_cat_build_key(sb, fd.search_key, cnid, NULL);
if (!hfs_brec_find(&fd)) if (!hfs_brec_find(&fd))
hfs_brec_remove(&fd); hfs_brec_remove(&fd);
err2: err2:
@ -176,7 +177,7 @@ int hfs_cat_find_brec(struct super_block *sb, u32 cnid,
hfs_cat_rec rec; hfs_cat_rec rec;
int res, len, type; int res, len, type;
hfs_cat_build_key(fd->search_key, cnid, NULL); hfs_cat_build_key(sb, fd->search_key, cnid, NULL);
res = hfs_brec_read(fd, &rec, sizeof(rec)); res = hfs_brec_read(fd, &rec, sizeof(rec));
if (res) if (res)
return res; return res;
@ -211,7 +212,7 @@ int hfs_cat_delete(u32 cnid, struct inode *dir, struct qstr *str)
sb = dir->i_sb; sb = dir->i_sb;
hfs_find_init(HFS_SB(sb)->cat_tree, &fd); hfs_find_init(HFS_SB(sb)->cat_tree, &fd);
hfs_cat_build_key(fd.search_key, dir->i_ino, str); hfs_cat_build_key(sb, fd.search_key, dir->i_ino, str);
res = hfs_brec_find(&fd); res = hfs_brec_find(&fd);
if (res) if (res)
goto out; goto out;
@ -239,7 +240,7 @@ int hfs_cat_delete(u32 cnid, struct inode *dir, struct qstr *str)
if (res) if (res)
goto out; goto out;
hfs_cat_build_key(fd.search_key, cnid, NULL); hfs_cat_build_key(sb, fd.search_key, cnid, NULL);
res = hfs_brec_find(&fd); res = hfs_brec_find(&fd);
if (!res) { if (!res) {
res = hfs_brec_remove(&fd); res = hfs_brec_remove(&fd);
@ -280,7 +281,7 @@ int hfs_cat_move(u32 cnid, struct inode *src_dir, struct qstr *src_name,
dst_fd = src_fd; dst_fd = src_fd;
/* find the old dir entry and read the data */ /* find the old dir entry and read the data */
hfs_cat_build_key(src_fd.search_key, src_dir->i_ino, src_name); hfs_cat_build_key(sb, src_fd.search_key, src_dir->i_ino, src_name);
err = hfs_brec_find(&src_fd); err = hfs_brec_find(&src_fd);
if (err) if (err)
goto out; goto out;
@ -289,7 +290,7 @@ int hfs_cat_move(u32 cnid, struct inode *src_dir, struct qstr *src_name,
src_fd.entrylength); src_fd.entrylength);
/* create new dir entry with the data from the old entry */ /* create new dir entry with the data from the old entry */
hfs_cat_build_key(dst_fd.search_key, dst_dir->i_ino, dst_name); hfs_cat_build_key(sb, dst_fd.search_key, dst_dir->i_ino, dst_name);
err = hfs_brec_find(&dst_fd); err = hfs_brec_find(&dst_fd);
if (err != -ENOENT) { if (err != -ENOENT) {
if (!err) if (!err)
@ -305,7 +306,7 @@ int hfs_cat_move(u32 cnid, struct inode *src_dir, struct qstr *src_name,
mark_inode_dirty(dst_dir); mark_inode_dirty(dst_dir);
/* finally remove the old entry */ /* finally remove the old entry */
hfs_cat_build_key(src_fd.search_key, src_dir->i_ino, src_name); hfs_cat_build_key(sb, src_fd.search_key, src_dir->i_ino, src_name);
err = hfs_brec_find(&src_fd); err = hfs_brec_find(&src_fd);
if (err) if (err)
goto out; goto out;
@ -321,7 +322,7 @@ int hfs_cat_move(u32 cnid, struct inode *src_dir, struct qstr *src_name,
goto out; goto out;
/* remove old thread entry */ /* remove old thread entry */
hfs_cat_build_key(src_fd.search_key, cnid, NULL); hfs_cat_build_key(sb, src_fd.search_key, cnid, NULL);
err = hfs_brec_find(&src_fd); err = hfs_brec_find(&src_fd);
if (err) if (err)
goto out; goto out;
@ -330,8 +331,8 @@ int hfs_cat_move(u32 cnid, struct inode *src_dir, struct qstr *src_name,
goto out; goto out;
/* create new thread entry */ /* create new thread entry */
hfs_cat_build_key(dst_fd.search_key, cnid, NULL); hfs_cat_build_key(sb, dst_fd.search_key, cnid, NULL);
entry_size = hfs_cat_build_thread(&entry, type == HFS_CDR_FIL ? HFS_CDR_FTH : HFS_CDR_THD, entry_size = hfs_cat_build_thread(sb, &entry, type == HFS_CDR_FIL ? HFS_CDR_FTH : HFS_CDR_THD,
dst_dir->i_ino, dst_name); dst_dir->i_ino, dst_name);
err = hfs_brec_find(&dst_fd); err = hfs_brec_find(&dst_fd);
if (err != -ENOENT) { if (err != -ENOENT) {

View file

@ -28,7 +28,7 @@ static struct dentry *hfs_lookup(struct inode *dir, struct dentry *dentry,
dentry->d_op = &hfs_dentry_operations; dentry->d_op = &hfs_dentry_operations;
hfs_find_init(HFS_SB(dir->i_sb)->cat_tree, &fd); hfs_find_init(HFS_SB(dir->i_sb)->cat_tree, &fd);
hfs_cat_build_key(fd.search_key, dir->i_ino, &dentry->d_name); hfs_cat_build_key(dir->i_sb, fd.search_key, dir->i_ino, &dentry->d_name);
res = hfs_brec_read(&fd, &rec, sizeof(rec)); res = hfs_brec_read(&fd, &rec, sizeof(rec));
if (res) { if (res) {
hfs_find_exit(&fd); hfs_find_exit(&fd);
@ -56,7 +56,7 @@ static int hfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
struct inode *inode = filp->f_dentry->d_inode; struct inode *inode = filp->f_dentry->d_inode;
struct super_block *sb = inode->i_sb; struct super_block *sb = inode->i_sb;
int len, err; int len, err;
char strbuf[HFS_NAMELEN + 1]; char strbuf[HFS_MAX_NAMELEN];
union hfs_cat_rec entry; union hfs_cat_rec entry;
struct hfs_find_data fd; struct hfs_find_data fd;
struct hfs_readdir_data *rd; struct hfs_readdir_data *rd;
@ -66,7 +66,7 @@ static int hfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
return 0; return 0;
hfs_find_init(HFS_SB(sb)->cat_tree, &fd); hfs_find_init(HFS_SB(sb)->cat_tree, &fd);
hfs_cat_build_key(fd.search_key, inode->i_ino, NULL); hfs_cat_build_key(sb, fd.search_key, inode->i_ino, NULL);
err = hfs_brec_find(&fd); err = hfs_brec_find(&fd);
if (err) if (err)
goto out; goto out;
@ -111,7 +111,7 @@ static int hfs_readdir(struct file *filp, void *dirent, filldir_t filldir)
} }
hfs_bnode_read(fd.bnode, &entry, fd.entryoffset, fd.entrylength); hfs_bnode_read(fd.bnode, &entry, fd.entryoffset, fd.entrylength);
type = entry.type; type = entry.type;
len = hfs_mac2triv(strbuf, &fd.key->cat.CName); len = hfs_mac2asc(sb, strbuf, &fd.key->cat.CName);
if (type == HFS_CDR_DIR) { if (type == HFS_CDR_DIR) {
if (fd.entrylength < sizeof(struct hfs_cat_dir)) { if (fd.entrylength < sizeof(struct hfs_cat_dir)) {
printk("HFS: small dir entry\n"); printk("HFS: small dir entry\n");
@ -307,7 +307,8 @@ static int hfs_rename(struct inode *old_dir, struct dentry *old_dentry,
old_dir, &old_dentry->d_name, old_dir, &old_dentry->d_name,
new_dir, &new_dentry->d_name); new_dir, &new_dentry->d_name);
if (!res) if (!res)
hfs_cat_build_key((btree_key *)&HFS_I(old_dentry->d_inode)->cat_key, hfs_cat_build_key(old_dir->i_sb,
(btree_key *)&HFS_I(old_dentry->d_inode)->cat_key,
new_dir->i_ino, &new_dentry->d_name); new_dir->i_ino, &new_dentry->d_name);
return res; return res;
} }

View file

@ -25,6 +25,7 @@
#define HFS_SECTOR_SIZE 512 /* size of an HFS sector */ #define HFS_SECTOR_SIZE 512 /* size of an HFS sector */
#define HFS_SECTOR_SIZE_BITS 9 /* log_2(HFS_SECTOR_SIZE) */ #define HFS_SECTOR_SIZE_BITS 9 /* log_2(HFS_SECTOR_SIZE) */
#define HFS_NAMELEN 31 /* maximum length of an HFS filename */ #define HFS_NAMELEN 31 /* maximum length of an HFS filename */
#define HFS_MAX_NAMELEN 128
#define HFS_MAX_VALENCE 32767U #define HFS_MAX_VALENCE 32767U
/* Meanings of the drAtrb field of the MDB, /* Meanings of the drAtrb field of the MDB,

View file

@ -141,6 +141,8 @@ struct hfs_sb_info {
int session, part; int session, part;
struct nls_table *nls_io, *nls_disk;
struct semaphore bitmap_lock; struct semaphore bitmap_lock;
unsigned long flags; unsigned long flags;
@ -168,7 +170,7 @@ extern int hfs_cat_create(u32, struct inode *, struct qstr *, struct inode *);
extern int hfs_cat_delete(u32, struct inode *, struct qstr *); extern int hfs_cat_delete(u32, struct inode *, struct qstr *);
extern int hfs_cat_move(u32, struct inode *, struct qstr *, extern int hfs_cat_move(u32, struct inode *, struct qstr *,
struct inode *, struct qstr *); struct inode *, struct qstr *);
extern void hfs_cat_build_key(btree_key *, u32, struct qstr *); extern void hfs_cat_build_key(struct super_block *, btree_key *, u32, struct qstr *);
/* dir.c */ /* dir.c */
extern struct file_operations hfs_dir_operations; extern struct file_operations hfs_dir_operations;
@ -222,8 +224,8 @@ extern int hfs_strcmp(const unsigned char *, unsigned int,
extern int hfs_compare_dentry(struct dentry *, struct qstr *, struct qstr *); extern int hfs_compare_dentry(struct dentry *, struct qstr *, struct qstr *);
/* trans.c */ /* trans.c */
extern void hfs_triv2mac(struct hfs_name *, struct qstr *); extern void hfs_asc2mac(struct super_block *, struct hfs_name *, struct qstr *);
extern int hfs_mac2triv(char *, const struct hfs_name *); extern int hfs_mac2asc(struct super_block *, char *, const struct hfs_name *);
extern struct timezone sys_tz; extern struct timezone sys_tz;

View file

@ -160,7 +160,7 @@ struct inode *hfs_new_inode(struct inode *dir, struct qstr *name, int mode)
init_MUTEX(&HFS_I(inode)->extents_lock); init_MUTEX(&HFS_I(inode)->extents_lock);
INIT_LIST_HEAD(&HFS_I(inode)->open_dir_list); INIT_LIST_HEAD(&HFS_I(inode)->open_dir_list);
hfs_cat_build_key((btree_key *)&HFS_I(inode)->cat_key, dir->i_ino, name); hfs_cat_build_key(sb, (btree_key *)&HFS_I(inode)->cat_key, dir->i_ino, name);
inode->i_ino = HFS_SB(sb)->next_id++; inode->i_ino = HFS_SB(sb)->next_id++;
inode->i_mode = mode; inode->i_mode = mode;
inode->i_uid = current->fsuid; inode->i_uid = current->fsuid;

View file

@ -10,6 +10,7 @@
#include <linux/cdrom.h> #include <linux/cdrom.h>
#include <linux/genhd.h> #include <linux/genhd.h>
#include <linux/nls.h>
#include "hfs_fs.h" #include "hfs_fs.h"
#include "btree.h" #include "btree.h"
@ -343,6 +344,11 @@ void hfs_mdb_put(struct super_block *sb)
brelse(HFS_SB(sb)->mdb_bh); brelse(HFS_SB(sb)->mdb_bh);
brelse(HFS_SB(sb)->alt_mdb_bh); brelse(HFS_SB(sb)->alt_mdb_bh);
if (HFS_SB(sb)->nls_io)
unload_nls(HFS_SB(sb)->nls_io);
if (HFS_SB(sb)->nls_disk)
unload_nls(HFS_SB(sb)->nls_disk);
kfree(HFS_SB(sb)); kfree(HFS_SB(sb));
sb->s_fs_info = NULL; sb->s_fs_info = NULL;
} }

View file

@ -17,6 +17,7 @@
#include <linux/blkdev.h> #include <linux/blkdev.h>
#include <linux/mount.h> #include <linux/mount.h>
#include <linux/init.h> #include <linux/init.h>
#include <linux/nls.h>
#include <linux/parser.h> #include <linux/parser.h>
#include <linux/seq_file.h> #include <linux/seq_file.h>
#include <linux/vfs.h> #include <linux/vfs.h>
@ -130,6 +131,10 @@ static int hfs_show_options(struct seq_file *seq, struct vfsmount *mnt)
seq_printf(seq, ",part=%u", sbi->part); seq_printf(seq, ",part=%u", sbi->part);
if (sbi->session >= 0) if (sbi->session >= 0)
seq_printf(seq, ",session=%u", sbi->session); seq_printf(seq, ",session=%u", sbi->session);
if (sbi->nls_disk)
seq_printf(seq, ",codepage=%s", sbi->nls_disk->charset);
if (sbi->nls_io)
seq_printf(seq, ",iocharset=%s", sbi->nls_io->charset);
if (sbi->s_quiet) if (sbi->s_quiet)
seq_printf(seq, ",quiet"); seq_printf(seq, ",quiet");
return 0; return 0;
@ -163,6 +168,7 @@ static struct super_operations hfs_super_operations = {
enum { enum {
opt_uid, opt_gid, opt_umask, opt_file_umask, opt_dir_umask, opt_uid, opt_gid, opt_umask, opt_file_umask, opt_dir_umask,
opt_part, opt_session, opt_type, opt_creator, opt_quiet, opt_part, opt_session, opt_type, opt_creator, opt_quiet,
opt_codepage, opt_iocharset,
opt_err opt_err
}; };
@ -177,6 +183,8 @@ static match_table_t tokens = {
{ opt_type, "type=%s" }, { opt_type, "type=%s" },
{ opt_creator, "creator=%s" }, { opt_creator, "creator=%s" },
{ opt_quiet, "quiet" }, { opt_quiet, "quiet" },
{ opt_codepage, "codepage=%s" },
{ opt_iocharset, "iocharset=%s" },
{ opt_err, NULL } { opt_err, NULL }
}; };
@ -282,11 +290,46 @@ static int parse_options(char *options, struct hfs_sb_info *hsb)
case opt_quiet: case opt_quiet:
hsb->s_quiet = 1; hsb->s_quiet = 1;
break; break;
case opt_codepage:
if (hsb->nls_disk) {
printk("HFS+-fs: unable to change codepage\n");
return 0;
}
p = match_strdup(&args[0]);
hsb->nls_disk = load_nls(p);
if (!hsb->nls_disk) {
printk("HFS+-fs: unable to load codepage \"%s\"\n", p);
kfree(p);
return 0;
}
kfree(p);
break;
case opt_iocharset:
if (hsb->nls_io) {
printk("HFS: unable to change iocharset\n");
return 0;
}
p = match_strdup(&args[0]);
hsb->nls_io = load_nls(p);
if (!hsb->nls_io) {
printk("HFS: unable to load iocharset \"%s\"\n", p);
kfree(p);
return 0;
}
kfree(p);
break;
default: default:
return 0; return 0;
} }
} }
if (hsb->nls_disk && !hsb->nls_io) {
hsb->nls_io = load_nls_default();
if (!hsb->nls_io) {
printk("HFS: unable to load default iocharset\n");
return 0;
}
}
hsb->s_dir_umask &= 0777; hsb->s_dir_umask &= 0777;
hsb->s_file_umask &= 0577; hsb->s_file_umask &= 0577;

View file

@ -9,12 +9,15 @@
* with ':' vs. '/' as the path-element separator. * with ':' vs. '/' as the path-element separator.
*/ */
#include <linux/types.h>
#include <linux/nls.h>
#include "hfs_fs.h" #include "hfs_fs.h"
/*================ Global functions ================*/ /*================ Global functions ================*/
/* /*
* hfs_mac2triv() * hfs_mac2asc()
* *
* Given a 'Pascal String' (a string preceded by a length byte) in * Given a 'Pascal String' (a string preceded by a length byte) in
* the Macintosh character set produce the corresponding filename using * the Macintosh character set produce the corresponding filename using
@ -27,23 +30,58 @@
* by ':' which never appears in HFS filenames. All other characters * by ':' which never appears in HFS filenames. All other characters
* are passed unchanged from input to output. * are passed unchanged from input to output.
*/ */
int hfs_mac2triv(char *out, const struct hfs_name *in) int hfs_mac2asc(struct super_block *sb, char *out, const struct hfs_name *in)
{ {
const char *p; struct nls_table *nls_disk = HFS_SB(sb)->nls_disk;
char c; struct nls_table *nls_io = HFS_SB(sb)->nls_io;
int i, len; const char *src;
char *dst;
int srclen, dstlen, size;
len = in->len; src = in->name;
p = in->name; srclen = in->len;
for (i = 0; i < len; i++) { dst = out;
c = *p++; dstlen = HFS_MAX_NAMELEN;
*out++ = c == '/' ? ':' : c; if (nls_io) {
wchar_t ch;
while (srclen > 0) {
if (nls_disk) {
size = nls_disk->char2uni(src, srclen, &ch);
if (size <= 0) {
ch = '?';
size = 1;
}
src += size;
srclen -= size;
} else {
ch = *src++;
srclen--;
}
if (ch == '/')
ch = ':';
size = nls_io->uni2char(ch, dst, dstlen);
if (size < 0) {
if (size == -ENAMETOOLONG)
goto out;
*dst = '?';
size = 1;
}
dst += size;
dstlen -= size;
}
} else {
char ch;
while (--srclen >= 0)
*dst++ = (ch = *src++) == '/' ? ':' : ch;
} }
return i; out:
return dst - out;
} }
/* /*
* hfs_triv2mac() * hfs_asc2mac()
* *
* Given an ASCII string (not null-terminated) and its length, * Given an ASCII string (not null-terminated) and its length,
* generate the corresponding filename in the Macintosh character set * generate the corresponding filename in the Macintosh character set
@ -54,19 +92,57 @@ int hfs_mac2triv(char *out, const struct hfs_name *in)
* This routine is a inverse to hfs_mac2triv(). * This routine is a inverse to hfs_mac2triv().
* A ':' is replaced by a '/'. * A ':' is replaced by a '/'.
*/ */
void hfs_triv2mac(struct hfs_name *out, struct qstr *in) void hfs_asc2mac(struct super_block *sb, struct hfs_name *out, struct qstr *in)
{ {
struct nls_table *nls_disk = HFS_SB(sb)->nls_disk;
struct nls_table *nls_io = HFS_SB(sb)->nls_io;
const char *src; const char *src;
char *dst, c; char *dst;
int i, len; int srclen, dstlen, size;
out->len = len = min((unsigned int)HFS_NAMELEN, in->len);
src = in->name; src = in->name;
srclen = in->len;
dst = out->name; dst = out->name;
for (i = 0; i < len; i++) { dstlen = HFS_NAMELEN;
c = *src++; if (nls_io) {
*dst++ = c == ':' ? '/' : c; wchar_t ch;
while (srclen > 0) {
size = nls_io->char2uni(src, srclen, &ch);
if (size < 0) {
ch = '?';
size = 1;
}
src += size;
srclen -= size;
if (ch == ':')
ch = '/';
if (nls_disk) {
size = nls_disk->uni2char(ch, dst, dstlen);
if (size < 0) {
if (size == -ENAMETOOLONG)
goto out;
*dst = '?';
size = 1;
}
dst += size;
dstlen -= size;
} else {
*dst++ = ch > 0xff ? '?' : ch;
dstlen--;
}
}
} else {
char ch;
if (dstlen > srclen)
dstlen = srclen;
while (--dstlen >= 0)
*dst++ = (ch = *src++) == ':' ? '/' : ch;
} }
for (; i < HFS_NAMELEN; i++) out:
out->len = dst - (char *)out->name;
dstlen = HFS_NAMELEN - out->len;
while (--dstlen >= 0)
*dst++ = 0; *dst++ = 0;
} }