/** => zzip_entry_findfile
*
* This function is the first call of all the zip access functions here.
* It contains the code to find the first entry of the zip central directory.
* Here we require the stdio handle to represent a real zip file where the
* disk_trailer is _last_ in the file area, so that its position would be at
* a fixed offset from the end of the file area if not for the comment field
* allowed to be of variable length (which needs us to do a little search
* for the disk_tailer). However, in this simple implementation we disregard
* any disk_trailer info telling about multidisk archives, so we just return
* a pointer to the first entry in the zip central directory of that file.
*
* For an actual means, we are going to search backwards from the end
* of the mmaped block looking for the PK-magic signature of a
* disk_trailer. If we see one then we check the rootseek value to
* find the first disk_entry of the root central directory. If we find
* the correct PK-magic signature of a disk_entry over there then we
* assume we are done and we are going to return a pointer to that label.
*
* The return value is a pointer to the first zzip_disk_entry being checked
* to be within the bounds of the file area specified by the arguments. If
* no disk_trailer was found then null is returned, and likewise we only
* accept a disk_trailer with a seekvalue that points to a disk_entry and
* both parts have valid PK-magic parts. Beyond some sanity check we try to
* catch a common brokeness with zip archives that still allows us to find
* the start of the zip central directory.
*/
zzip__new__ ZZIP_ENTRY *
zzip_entry_findfirst(FILE * disk)
{
if (! disk)
return 0;
if (fseeko(disk, 0, SEEK_END) == -1)
return 0;
___ zzip_off_t disksize = ftello(disk);
if (disksize < (zzip_off_t) sizeof(struct zzip_disk_trailer))
return 0;
/* we read out chunks of 8 KiB in the hope to match disk granularity */
___ zzip_off_t pagesize = PAGESIZE; /* getpagesize() */
___ ZZIP_ENTRY *entry = malloc(sizeof(*entry));
if (! entry)
return 0;
___ unsigned char *buffer = malloc(pagesize);
if (! buffer)
goto nomem;
assert(pagesize / 2 > (zzip_off_t) sizeof(struct zzip_disk_trailer));
/* at each step, we will fread a pagesize block which overlaps with the
* previous read by means of pagesize/2 step at the end of the while(1) */
___ zzip_off_t mapoffs = disksize & ~(pagesize - 1);
___ zzip_off_t mapsize = disksize - mapoffs;
if (mapoffs && mapsize < pagesize / 2)
{
mapoffs -= pagesize / 2;
mapsize += pagesize / 2;
}
while (1)
{
if (fseeko(disk, mapoffs, SEEK_SET) == -1)
goto error;
if (fread(buffer, 1, mapsize, disk) != mapsize)
goto error;
___ unsigned char *p =
buffer + mapsize - sizeof(struct zzip_disk_trailer);
for (; p >= buffer; p--)
{
zzip_off_t root; /* (struct zzip_disk_entry*) */
if (zzip_disk_trailer_check_magic(p))
{
root = zzip_disk_trailer_rootseek((struct zzip_disk_trailer *)
p);
if (root > disksize - (long) sizeof(struct zzip_disk_trailer))
{
/* first disk_entry is after the disk_trailer? can't be! */
struct zzip_disk_trailer *trailer =
(struct zzip_disk_trailer *) p;
zzip_off_t rootsize = zzip_disk_trailer_rootsize(trailer);
if (rootsize > mapoffs)
continue;
/* a common brokeness that can be fixed: we just assume the
* central directory was written directly before : */
root = mapoffs - rootsize;
}
} else if (zzip_disk64_trailer_check_magic(p))
{
struct zzip_disk64_trailer *trailer =
(struct zzip_disk64_trailer *) p;
if (sizeof(zzip_off_t) < 8)
return 0;
root = zzip_disk64_trailer_rootseek(trailer);
} else
continue;
assert(0 <= root && root < mapsize);
if (fseeko(disk, root, SEEK_SET) == -1)
goto error;
if (fread(disk_(entry), 1, sizeof(*disk_(entry)), disk)
!= sizeof(*disk_(entry))) goto error;
if (zzip_disk_entry_check_magic(entry))
{
free(buffer);
entry->headseek = root;
entry->diskfile = disk;
entry->disksize = disksize;
if (prescan_entry(entry))
goto nomem;
return entry;
}
}
____;
if (! mapoffs)
break;
assert(mapsize >= pagesize / 2);
mapoffs -= pagesize / 2; /* mapsize += pagesize/2; */
mapsize = pagesize; /* if (mapsize > pagesize) ... */
if (disksize - mapoffs > 64 * 1024)
break;
}
error:
free(buffer);
nomem:
free(entry);
____;
____;
____;
____;
____;
____;
return 0;
}
/** => zzip_entry_findfile
*
* This function is the first call of all the zip access functions here.
* It contains the code to find the first entry of the zip central directory.
* Here we require the stdio handle to represent a real zip file where the
* disk_trailer is _last_ in the file area, so that its position would be at
* a fixed offset from the end of the file area if not for the comment field
* allowed to be of variable length (which needs us to do a little search
* for the disk_tailer). However, in this simple implementation we disregard
* any disk_trailer info telling about multidisk archives, so we just return
* a pointer to the first entry in the zip central directory of that file.
*
* For an actual means, we are going to search backwards from the end
* of the mmaped block looking for the PK-magic signature of a
* disk_trailer. If we see one then we check the rootseek value to
* find the first disk_entry of the root central directory. If we find
* the correct PK-magic signature of a disk_entry over there then we
* assume we are done and we are going to return a pointer to that label.
*
* The return value is a pointer to the first zzip_disk_entry being checked
* to be within the bounds of the file area specified by the arguments. If
* no disk_trailer was found then null is returned, and likewise we only
* accept a disk_trailer with a seekvalue that points to a disk_entry and
* both parts have valid PK-magic parts. Beyond some sanity check we try to
* catch a common brokeness with zip archives that still allows us to find
* the start of the zip central directory.
*/
ZZIP_ENTRY* _zzip_restrict
zzip_entry_findfirst(FILE* disk)
{
if (! disk) return 0;
fseeko (disk, 0, SEEK_END);
___ zzip_off_t disksize = ftello (disk);
if (disksize < (zzip_off_t) sizeof(struct zzip_disk_trailer)) return 0;
/* we read out chunks of 8 KiB in the hope to match disk granularity */
___ zzip_off_t pagesize = PAGESIZE; /* getpagesize() */
___ ZZIP_ENTRY* entry = malloc (sizeof(*entry)); if (! entry) return 0;
___ char* buffer = malloc (pagesize); if (! buffer) goto nomem;
assert (pagesize/2 > (zzip_off_t) sizeof (struct zzip_disk_trailer));
/* at each step, we will fread a pagesize block which overlaps with the
* previous read by means of pagesize/2 step at the end of the while(1) */
___ zzip_off_t mapoffs = disksize &~ (pagesize-1);
___ zzip_off_t mapsize = disksize - mapoffs;
if (mapoffs && mapsize < pagesize/2) {
mapoffs -= pagesize/2; mapsize += pagesize/2; }
while(1)
{
fseeko (disk, mapoffs, SEEK_SET);
fread (buffer, 1, mapsize, disk);
___ char* p = buffer + mapsize - sizeof(struct zzip_disk_trailer);
for (; p >= buffer ; p--)
{
if (! zzip_disk_trailer_check_magic(p)) continue;
___ zzip_off_t root =
zzip_disk_trailer_rootseek ((struct zzip_disk_trailer*)p);
if ((char*) root > p)
{ /* the first disk_entry is after the disk_trailer? can't be! */
zzip_off_t rootsize =
zzip_disk_trailer_rootsize ((struct zzip_disk_trailer*)p);
if (rootsize > mapoffs) continue;
/* a common brokeness that can be fixed: we just assume that
* the central directory was written directly before : */
root = mapoffs - rootsize;
}
assert (0 <= root && root < mapsize);
fseeko (disk, root, SEEK_SET);
fread (disk_(entry), 1, sizeof(*disk_(entry)), disk);
if (zzip_disk_entry_check_magic(entry))
{
free (buffer);
entry->headseek = root;
entry->diskfile = disk;
entry->disksize = disksize;
___ zzip_size_t tailsize =
zzip_disk_entry_sizeof_tails (disk_(entry));
if (!( entry->tail = malloc (tailsize+1) )) goto nomem;
fread (entry->tail, 1, tailsize, disk);
entry->tailalloc = tailsize+1;
return entry; ____;
}
____;
} ____;
if (! mapoffs) break; assert (mapsize >= pagesize/2);
mapoffs -= pagesize/2; /* mapsize += pagesize/2; */
mapsize = pagesize; /* if (mapsize > pagesize) ... */
if (disksize - mapoffs > 64*1024) break;
}
free (buffer);
nomem:
free (entry); ____;____;____;____;____;____;
return 0;
}
