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ROSE/dosfs/dosfs.c
Lucia Ceionia ddadeed70c Added a hex viewer, Fixed a bug in dosfs
2023-02-04 18:51:09 -06:00

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/*
DOSFS Embedded FAT-Compatible Filesystem
(C) 2005 Lewin A.R.W. Edwards (sysadm@zws.com)
You are permitted to modify and/or use this code in your own projects without
payment of royalty, regardless of the license(s) you choose for those projects.
You cannot re-copyright or restrict use of the code as released by Lewin Edwards.
*/
#include "dosfs.h"
#include "tmpstring.c"
#include "../interrupt.h"
#include "../v86defs.h"
uint32_t DFS_ReadSector(uint8_t unit, uint8_t *buffer, uint32_t sector, uint32_t count) {
// NOTE If the buffer provided is outside the 0x20000-0x2FE00 range,
// the function will use that buffer for the Virtual 8086 process
// and copy to the other buffer after
uint8_t *v86buf = buffer;
if ((uintptr_t)v86buf < 0x20000 || (uintptr_t)v86buf > 0x2FE00)
v86buf = (uint8_t *)0x20000;
v86disk_addr_packet.start_block = sector;
v86disk_addr_packet.blocks = count;
v86disk_addr_packet.transfer_buffer =
(uintptr_t)v86buf & 0x000F |
(((uintptr_t)v86buf & 0xFFFF0) << 12);
union V86Regs_t regs;
FARPTR v86_entry = i386LinearToFp(v86DiskRead);
enter_v86(0x8000, 0xFF00, FP_SEG(v86_entry), FP_OFF(v86_entry), &regs);
if (v86buf != buffer)
memcpy(buffer, v86buf, count * SECTOR_SIZE);
return 0;
}
uint32_t DFS_WriteSector(uint8_t unit, uint8_t *buffer, uint32_t sector, uint32_t count) {
for(;;);
}
/*
Get starting sector# of specified partition on drive #unit
NOTE: This code ASSUMES an MBR on the disk.
scratchsector should point to a SECTOR_SIZE scratch area
Returns 0xffffffff for any error.
If pactive is non-NULL, this function also returns the partition active flag.
If pptype is non-NULL, this function also returns the partition type.
If psize is non-NULL, this function also returns the partition size.
*/
uint32_t DFS_GetPtnStart(uint8_t unit, uint8_t *scratchsector, uint8_t pnum, uint8_t *pactive, uint8_t *pptype, uint32_t *psize)
{
uint32_t result;
PMBR mbr = (PMBR) scratchsector;
// DOS ptable supports maximum 4 partitions
if (pnum > 3)
return DFS_ERRMISC;
// Read MBR from target media
if (DFS_ReadSector(unit,scratchsector,0,1)) {
return DFS_ERRMISC;
}
result = (uint32_t) mbr->ptable[pnum].start_0 |
(((uint32_t) mbr->ptable[pnum].start_1) << 8) |
(((uint32_t) mbr->ptable[pnum].start_2) << 16) |
(((uint32_t) mbr->ptable[pnum].start_3) << 24);
if (pactive)
*pactive = mbr->ptable[pnum].active;
if (pptype)
*pptype = mbr->ptable[pnum].type;
if (psize)
*psize = (uint32_t) mbr->ptable[pnum].size_0 |
(((uint32_t) mbr->ptable[pnum].size_1) << 8) |
(((uint32_t) mbr->ptable[pnum].size_2) << 16) |
(((uint32_t) mbr->ptable[pnum].size_3) << 24);
return result;
}
/*
Retrieve volume info from BPB and store it in a VOLINFO structure
You must provide the unit and starting sector of the filesystem, and
a pointer to a sector buffer for scratch
Attempts to read BPB and glean information about the FS from that.
Returns 0 OK, nonzero for any error.
*/
uint32_t DFS_GetVolInfo(uint8_t unit, uint8_t *scratchsector, uint32_t startsector, PVOLINFO volinfo)
{
PLBR lbr = (PLBR) scratchsector;
volinfo->unit = unit;
volinfo->startsector = startsector;
if(DFS_ReadSector(unit,scratchsector,startsector,1))
return DFS_ERRMISC;
// tag: OEMID, refer dosfs.h
// strncpy(volinfo->oemid, lbr->oemid, 8);
// volinfo->oemid[8] = 0;
volinfo->secperclus = lbr->bpb.secperclus;
volinfo->reservedsecs = (uint16_t) lbr->bpb.reserved_l |
(((uint16_t) lbr->bpb.reserved_h) << 8);
volinfo->numsecs = (uint16_t) lbr->bpb.sectors_s_l |
(((uint16_t) lbr->bpb.sectors_s_h) << 8);
if (!volinfo->numsecs)
volinfo->numsecs = (uint32_t) lbr->bpb.sectors_l_0 |
(((uint32_t) lbr->bpb.sectors_l_1) << 8) |
(((uint32_t) lbr->bpb.sectors_l_2) << 16) |
(((uint32_t) lbr->bpb.sectors_l_3) << 24);
// If secperfat is 0, we must be in a FAT32 volume; get secperfat
// from the FAT32 EBPB. The volume label and system ID string are also
// in different locations for FAT12/16 vs FAT32.
volinfo->secperfat = (uint16_t) lbr->bpb.secperfat_l |
(((uint16_t) lbr->bpb.secperfat_h) << 8);
if (!volinfo->secperfat) {
volinfo->secperfat = (uint32_t) lbr->ebpb.ebpb32.fatsize_0 |
(((uint32_t) lbr->ebpb.ebpb32.fatsize_1) << 8) |
(((uint32_t) lbr->ebpb.ebpb32.fatsize_2) << 16) |
(((uint32_t) lbr->ebpb.ebpb32.fatsize_3) << 24);
memcpy(volinfo->label, lbr->ebpb.ebpb32.label, 11);
volinfo->label[11] = 0;
// tag: OEMID, refer dosfs.h
// memcpy(volinfo->system, lbr->ebpb.ebpb32.system, 8);
// volinfo->system[8] = 0;
}
else {
memcpy(volinfo->label, lbr->ebpb.ebpb.label, 11);
volinfo->label[11] = 0;
// tag: OEMID, refer dosfs.h
// memcpy(volinfo->system, lbr->ebpb.ebpb.system, 8);
// volinfo->system[8] = 0;
}
// note: if rootentries is 0, we must be in a FAT32 volume.
volinfo->rootentries = (uint16_t) lbr->bpb.rootentries_l |
(((uint16_t) lbr->bpb.rootentries_h) << 8);
// after extracting raw info we perform some useful precalculations
volinfo->fat1 = startsector + volinfo->reservedsecs;
// The calculation below is designed to round up the root directory size for FAT12/16
// and to simply ignore the root directory for FAT32, since it's a normal, expandable
// file in that situation.
if (volinfo->rootentries) {
volinfo->rootdir = volinfo->fat1 + (volinfo->secperfat * 2);
volinfo->dataarea = volinfo->rootdir + (((volinfo->rootentries * 32) + (SECTOR_SIZE - 1)) / SECTOR_SIZE);
}
else {
volinfo->dataarea = volinfo->fat1 + (volinfo->secperfat * 2);
volinfo->rootdir = (uint32_t) lbr->ebpb.ebpb32.root_0 |
(((uint32_t) lbr->ebpb.ebpb32.root_1) << 8) |
(((uint32_t) lbr->ebpb.ebpb32.root_2) << 16) |
(((uint32_t) lbr->ebpb.ebpb32.root_3) << 24);
}
// Calculate number of clusters in data area and infer FAT type from this information.
volinfo->numclusters = (volinfo->numsecs - volinfo->dataarea) / volinfo->secperclus;
if (volinfo->numclusters < 4085)
volinfo->filesystem = FAT12;
else if (volinfo->numclusters < 65525)
volinfo->filesystem = FAT16;
else
volinfo->filesystem = FAT32;
return DFS_OK;
}
/*
Fetch FAT entry for specified cluster number
You must provide a scratch buffer for one sector (SECTOR_SIZE) and a populated VOLINFO
Returns a FAT32 BAD_CLUSTER value for any error, otherwise the contents of the desired
FAT entry.
scratchcache should point to a UINT32. This variable caches the physical sector number
last read into the scratch buffer for performance enhancement reasons.
*/
uint32_t DFS_GetFAT(PVOLINFO volinfo, uint8_t *scratch, uint32_t *scratchcache, uint32_t cluster)
{
uint32_t offset, sector, result;
if (volinfo->filesystem == FAT12) {
offset = cluster + (cluster / 2);
}
else if (volinfo->filesystem == FAT16) {
offset = cluster * 2;
}
else if (volinfo->filesystem == FAT32) {
offset = cluster * 4;
}
else
return 0x0ffffff7; // FAT32 bad cluster
// at this point, offset is the BYTE offset of the desired sector from the start
// of the FAT. Calculate the physical sector containing this FAT entry.
sector = ldiv(offset, SECTOR_SIZE).quot + volinfo->fat1;
// If this is not the same sector we last read, then read it into RAM
if (sector != *scratchcache) {
if(DFS_ReadSector(volinfo->unit, scratch, sector, 1)) {
// avoid anyone assuming that this cache value is still valid, which
// might cause disk corruption
*scratchcache = 0;
return 0x0ffffff7; // FAT32 bad cluster
}
*scratchcache = sector;
}
// At this point, we "merely" need to extract the relevant entry.
// This is easy for FAT16 and FAT32, but a royal PITA for FAT12 as a single entry
// may span a sector boundary. The normal way around this is always to read two
// FAT sectors, but that luxury is (by design intent) unavailable to DOSFS.
offset = ldiv(offset, SECTOR_SIZE).rem;
if (volinfo->filesystem == FAT12) {
// Special case for sector boundary - Store last byte of current sector.
// Then read in the next sector and put the first byte of that sector into
// the high byte of result.
if (offset == SECTOR_SIZE - 1) {
result = (uint32_t) scratch[offset];
sector++;
if(DFS_ReadSector(volinfo->unit, scratch, sector, 1)) {
// avoid anyone assuming that this cache value is still valid, which
// might cause disk corruption
*scratchcache = 0;
return 0x0ffffff7; // FAT32 bad cluster
}
*scratchcache = sector;
// Thanks to Claudio Leonel for pointing out this missing line.
result |= ((uint32_t) scratch[0]) << 8;
}
else {
result = (uint32_t) scratch[offset] |
((uint32_t) scratch[offset+1]) << 8;
}
if (cluster & 1)
result = result >> 4;
else
result = result & 0xfff;
}
else if (volinfo->filesystem == FAT16) {
result = (uint32_t) scratch[offset] |
((uint32_t) scratch[offset+1]) << 8;
}
else if (volinfo->filesystem == FAT32) {
result = ((uint32_t) scratch[offset] |
((uint32_t) scratch[offset+1]) << 8 |
((uint32_t) scratch[offset+2]) << 16 |
((uint32_t) scratch[offset+3]) << 24) & 0x0fffffff;
}
else
result = 0x0ffffff7; // FAT32 bad cluster
return result;
}
/*
Set FAT entry for specified cluster number
You must provide a scratch buffer for one sector (SECTOR_SIZE) and a populated VOLINFO
Returns DFS_ERRMISC for any error, otherwise DFS_OK
scratchcache should point to a UINT32. This variable caches the physical sector number
last read into the scratch buffer for performance enhancement reasons.
NOTE: This code is HIGHLY WRITE-INEFFICIENT, particularly for flash media. Considerable
performance gains can be realized by caching the sector. However this is difficult to
achieve on FAT12 without requiring 2 sector buffers of scratch space, and it is a design
requirement of this code to operate on a single 512-byte scratch.
If you are operating DOSFS over flash, you are strongly advised to implement a writeback
cache in your physical I/O driver. This will speed up your code significantly and will
also conserve power and flash write life.
*/
uint32_t DFS_SetFAT(PVOLINFO volinfo, uint8_t *scratch, uint32_t *scratchcache, uint32_t cluster, uint32_t new_contents)
{
uint32_t offset, sector, result;
if (volinfo->filesystem == FAT12) {
offset = cluster + (cluster / 2);
new_contents &=0xfff;
}
else if (volinfo->filesystem == FAT16) {
offset = cluster * 2;
new_contents &=0xffff;
}
else if (volinfo->filesystem == FAT32) {
offset = cluster * 4;
new_contents &=0x0fffffff; // FAT32 is really "FAT28"
}
else
return DFS_ERRMISC;
// at this point, offset is the BYTE offset of the desired sector from the start
// of the FAT. Calculate the physical sector containing this FAT entry.
sector = ldiv(offset, SECTOR_SIZE).quot + volinfo->fat1;
// If this is not the same sector we last read, then read it into RAM
if (sector != *scratchcache) {
if(DFS_ReadSector(volinfo->unit, scratch, sector, 1)) {
// avoid anyone assuming that this cache value is still valid, which
// might cause disk corruption
*scratchcache = 0;
return DFS_ERRMISC;
}
*scratchcache = sector;
}
// At this point, we "merely" need to extract the relevant entry.
// This is easy for FAT16 and FAT32, but a royal PITA for FAT12 as a single entry
// may span a sector boundary. The normal way around this is always to read two
// FAT sectors, but that luxury is (by design intent) unavailable to DOSFS.
offset = ldiv(offset, SECTOR_SIZE).rem;
if (volinfo->filesystem == FAT12) {
// If this is an odd cluster, pre-shift the desired new contents 4 bits to
// make the calculations below simpler
if (cluster & 1)
new_contents = new_contents << 4;
// Special case for sector boundary
if (offset == SECTOR_SIZE - 1) {
// Odd cluster: High 12 bits being set
if (cluster & 1) {
scratch[offset] = (scratch[offset] & 0x0f) | new_contents & 0xf0;
}
// Even cluster: Low 12 bits being set
else {
scratch[offset] = new_contents & 0xff;
}
result = DFS_WriteSector(volinfo->unit, scratch, *scratchcache, 1);
// mirror the FAT into copy 2
if (DFS_OK == result)
result = DFS_WriteSector(volinfo->unit, scratch, (*scratchcache)+volinfo->secperfat, 1);
// If we wrote that sector OK, then read in the subsequent sector
// and poke the first byte with the remainder of this FAT entry.
if (DFS_OK == result) {
*scratchcache++;
result = DFS_ReadSector(volinfo->unit, scratch, *scratchcache, 1);
if (DFS_OK == result) {
// Odd cluster: High 12 bits being set
if (cluster & 1) {
scratch[0] = new_contents & 0xff00;
}
// Even cluster: Low 12 bits being set
else {
scratch[0] = (scratch[0] & 0xf0) | new_contents & 0x0f;
}
result = DFS_WriteSector(volinfo->unit, scratch, *scratchcache, 1);
// mirror the FAT into copy 2
if (DFS_OK == result)
result = DFS_WriteSector(volinfo->unit, scratch, (*scratchcache)+volinfo->secperfat, 1);
}
else {
// avoid anyone assuming that this cache value is still valid, which
// might cause disk corruption
*scratchcache = 0;
}
}
} // if (offset == SECTOR_SIZE - 1)
// Not a sector boundary. But we still have to worry about if it's an odd
// or even cluster number.
else {
// Odd cluster: High 12 bits being set
if (cluster & 1) {
scratch[offset] = (scratch[offset] & 0x0f) | new_contents & 0xf0;
scratch[offset+1] = new_contents & 0xff00;
}
// Even cluster: Low 12 bits being set
else {
scratch[offset] = new_contents & 0xff;
scratch[offset+1] = (scratch[offset+1] & 0xf0) | new_contents & 0x0f;
}
result = DFS_WriteSector(volinfo->unit, scratch, *scratchcache, 1);
// mirror the FAT into copy 2
if (DFS_OK == result)
result = DFS_WriteSector(volinfo->unit, scratch, (*scratchcache)+volinfo->secperfat, 1);
}
}
else if (volinfo->filesystem == FAT16) {
scratch[offset] = (new_contents & 0xff);
scratch[offset+1] = (new_contents & 0xff00) >> 8;
result = DFS_WriteSector(volinfo->unit, scratch, *scratchcache, 1);
// mirror the FAT into copy 2
if (DFS_OK == result)
result = DFS_WriteSector(volinfo->unit, scratch, (*scratchcache)+volinfo->secperfat, 1);
}
else if (volinfo->filesystem == FAT32) {
scratch[offset] = (new_contents & 0xff);
scratch[offset+1] = (new_contents & 0xff00) >> 8;
scratch[offset+2] = (new_contents & 0xff0000) >> 16;
scratch[offset+3] = (scratch[offset+3] & 0xf0) | ((new_contents & 0x0f000000) >> 24);
// Note well from the above: Per Microsoft's guidelines we preserve the upper
// 4 bits of the FAT32 cluster value. It's unclear what these bits will be used
// for; in every example I've encountered they are always zero.
result = DFS_WriteSector(volinfo->unit, scratch, *scratchcache, 1);
// mirror the FAT into copy 2
if (DFS_OK == result)
result = DFS_WriteSector(volinfo->unit, scratch, (*scratchcache)+volinfo->secperfat, 1);
}
else
result = DFS_ERRMISC;
return result;
}
/*
Convert a filename element from canonical (8.3) to directory entry (11) form
src must point to the first non-separator character.
dest must point to a 12-byte buffer.
*/
uint8_t *DFS_CanonicalToDir(uint8_t *dest, uint8_t *src)
{
uint8_t *destptr = dest;
memset(dest, ' ', 11);
dest[11] = 0;
while (*src && (*src != DIR_SEPARATOR) && (destptr - dest < 11)) {
if (*src >= 'a' && *src <='z') {
*destptr++ = (*src - 'a') + 'A';
src++;
}
else if (*src == '.') {
src++;
destptr = dest + 8;
}
else {
*destptr++ = *src++;
}
}
return dest;
}
/*
Find the first unused FAT entry
You must provide a scratch buffer for one sector (SECTOR_SIZE) and a populated VOLINFO
Returns a FAT32 BAD_CLUSTER value for any error, otherwise the contents of the desired
FAT entry.
Returns FAT32 bad_sector (0x0ffffff7) if there is no free cluster available
*/
uint32_t DFS_GetFreeFAT(PVOLINFO volinfo, uint8_t *scratch)
{
uint32_t i, result = 0xffffffff, scratchcache = 0;
// Search starts at cluster 2, which is the first usable cluster
// NOTE: This search can't terminate at a bad cluster, because there might
// legitimately be bad clusters on the disk.
for (i=2; i < volinfo->numclusters; i++) {
result = DFS_GetFAT(volinfo, scratch, &scratchcache, i);
if (!result) {
return i;
}
}
return 0x0ffffff7; // Can't find a free cluster
}
/*
Open a directory for enumeration by DFS_GetNextDirEnt
You must supply a populated VOLINFO (see DFS_GetVolInfo)
The empty string or a string containing only the directory separator are
considered to be the root directory.
Returns 0 OK, nonzero for any error.
*/
uint32_t DFS_OpenDir(PVOLINFO volinfo, uint8_t *dirname, PDIRINFO dirinfo)
{
// Default behavior is a regular search for existing entries
dirinfo->flags = 0;
if (!strlen((char *) dirname) || (strlen((char *) dirname) == 1 && dirname[0] == DIR_SEPARATOR)) {
if (volinfo->filesystem == FAT32) {
dirinfo->currentcluster = volinfo->rootdir;
dirinfo->currentsector = 0;
dirinfo->currententry = 0;
// read first sector of directory
return DFS_ReadSector(volinfo->unit, dirinfo->scratch, volinfo->dataarea + ((volinfo->rootdir - 2) * volinfo->secperclus), 1);
}
else {
dirinfo->currentcluster = 0;
dirinfo->currentsector = 0;
dirinfo->currententry = 0;
// read first sector of directory
return DFS_ReadSector(volinfo->unit, dirinfo->scratch, volinfo->rootdir, 1);
}
}
// This is not the root directory. We need to find the start of this subdirectory.
// We do this by devious means, using our own companion function DFS_GetNext.
else {
uint8_t tmpfn[12];
uint8_t *ptr = dirname;
uint32_t result;
DIRENT de;
if (volinfo->filesystem == FAT32) {
dirinfo->currentcluster = volinfo->rootdir;
dirinfo->currentsector = 0;
dirinfo->currententry = 0;
// read first sector of directory
if (DFS_ReadSector(volinfo->unit, dirinfo->scratch, volinfo->dataarea + ((volinfo->rootdir - 2) * volinfo->secperclus), 1))
return DFS_ERRMISC;
}
else {
dirinfo->currentcluster = 0;
dirinfo->currentsector = 0;
dirinfo->currententry = 0;
// read first sector of directory
if (DFS_ReadSector(volinfo->unit, dirinfo->scratch, volinfo->rootdir, 1))
return DFS_ERRMISC;
}
// skip leading path separators
while (*ptr == DIR_SEPARATOR && *ptr)
ptr++;
// Scan the path from left to right, finding the start cluster of each entry
// Observe that this code is inelegant, but obviates the need for recursion.
while (*ptr) {
DFS_CanonicalToDir(tmpfn, ptr);
de.name[0] = 0;
do {
result = DFS_GetNext(volinfo, dirinfo, &de);
} while (!result && memcmp(de.name, tmpfn, 11));
if (!memcmp(de.name, tmpfn, 11) && ((de.attr & ATTR_DIRECTORY) == ATTR_DIRECTORY)) {
if (volinfo->filesystem == FAT32) {
dirinfo->currentcluster = (uint32_t) de.startclus_l_l |
((uint32_t) de.startclus_l_h) << 8 |
((uint32_t) de.startclus_h_l) << 16 |
((uint32_t) de.startclus_h_h) << 24;
}
else {
dirinfo->currentcluster = (uint32_t) de.startclus_l_l |
((uint32_t) de.startclus_l_h) << 8;
}
dirinfo->currentsector = 0;
dirinfo->currententry = 0;
if (DFS_ReadSector(volinfo->unit, dirinfo->scratch, volinfo->dataarea + ((dirinfo->currentcluster - 2) * volinfo->secperclus), 1))
return DFS_ERRMISC;
}
else if (!memcmp(de.name, tmpfn, 11) && !(de.attr & ATTR_DIRECTORY))
return DFS_NOTFOUND;
// seek to next item in list
while (*ptr != DIR_SEPARATOR && *ptr)
ptr++;
if (*ptr == DIR_SEPARATOR)
ptr++;
}
if (!dirinfo->currentcluster)
return DFS_NOTFOUND;
}
return DFS_OK;
}
/*
Get next entry in opened directory structure. Copies fields into the dirent
structure, updates dirinfo. Note that it is the _caller's_ responsibility to
handle the '.' and '..' entries.
A deleted file will be returned as a NULL entry (first char of filename=0)
by this code. Filenames beginning with 0x05 will be translated to 0xE5
automatically. Long file name entries will be returned as NULL.
returns DFS_EOF if there are no more entries, DFS_OK if this entry is valid,
or DFS_ERRMISC for a media error
*/
uint32_t DFS_GetNext(PVOLINFO volinfo, PDIRINFO dirinfo, PDIRENT dirent)
{
uint32_t tempint; // required by DFS_GetFAT
// Do we need to read the next sector of the directory?
if (dirinfo->currententry >= SECTOR_SIZE / sizeof(DIRENT)) {
dirinfo->currententry = 0;
dirinfo->currentsector++;
// Root directory; special case handling
// Note that currentcluster will only ever be zero if both:
// (a) this is the root directory, and
// (b) we are on a FAT12/16 volume, where the root dir can't be expanded
if (dirinfo->currentcluster == 0) {
// Trying to read past end of root directory?
if (dirinfo->currentsector * (SECTOR_SIZE / sizeof(DIRENT)) >= volinfo->rootentries)
return DFS_EOF;
// Otherwise try to read the next sector
if (DFS_ReadSector(volinfo->unit, dirinfo->scratch, volinfo->rootdir + dirinfo->currentsector, 1))
return DFS_ERRMISC;
}
// Normal handling
else {
if (dirinfo->currentsector >= volinfo->secperclus) {
dirinfo->currentsector = 0;
if ((dirinfo->currentcluster >= 0xff7 && volinfo->filesystem == FAT12) ||
(dirinfo->currentcluster >= 0xfff7 && volinfo->filesystem == FAT16) ||
(dirinfo->currentcluster >= 0x0ffffff7 && volinfo->filesystem == FAT32)) {
// We are at the end of the directory chain. If this is a normal
// find operation, we should indicate that there is nothing more
// to see.
if (!(dirinfo->flags & DFS_DI_BLANKENT))
return DFS_EOF;
// On the other hand, if this is a "find free entry" search,
// we need to tell the caller to allocate a new cluster
else
return DFS_ALLOCNEW;
}
dirinfo->currentcluster = DFS_GetFAT(volinfo, dirinfo->scratch, &tempint, dirinfo->currentcluster);
}
if (DFS_ReadSector(volinfo->unit, dirinfo->scratch, volinfo->dataarea + ((dirinfo->currentcluster - 2) * volinfo->secperclus) + dirinfo->currentsector, 1))
return DFS_ERRMISC;
}
}
memcpy(dirent, &(((PDIRENT) dirinfo->scratch)[dirinfo->currententry]), sizeof(DIRENT));
if (dirent->name[0] == 0) { // no more files in this directory
// If this is a "find blank" then we can reuse this name.
if (dirinfo->flags & DFS_DI_BLANKENT)
return DFS_OK;
else
return DFS_EOF;
}
if (dirent->name[0] == 0xe5) // handle deleted file entries
dirent->name[0] = 0;
else if ((dirent->attr & ATTR_LONG_NAME) == ATTR_LONG_NAME)
dirent->name[0] = 0;
else if (dirent->name[0] == 0x05) // handle kanji filenames beginning with 0xE5
dirent->name[0] = 0xe5;
dirinfo->currententry++;
return DFS_OK;
}
/*
INTERNAL
Find a free directory entry in the directory specified by path
This function MAY cause a disk write if it is necessary to extend the directory
size.
Note - di.scratch must be preinitialized to point to a sector scratch buffer
de is a scratch structure
Returns DFS_ERRMISC if a new entry could not be located or created
de is updated with the same return information you would expect from DFS_GetNext
*/
uint32_t DFS_GetFreeDirEnt(PVOLINFO volinfo, uint8_t *path, PDIRINFO di, PDIRENT de)
{
uint32_t tempclus,i;
if (DFS_OpenDir(volinfo, path, di))
return DFS_NOTFOUND;
// Set "search for empty" flag so DFS_GetNext knows what we're doing
di->flags |= DFS_DI_BLANKENT;
// We seek through the directory looking for an empty entry
// Note we are reusing tempclus as a temporary result holder.
tempclus = 0;
do {
tempclus = DFS_GetNext(volinfo, di, de);
// Empty entry found
if (tempclus == DFS_OK && (!de->name[0])) {
return DFS_OK;
}
// End of root directory reached
else if (tempclus == DFS_EOF)
return DFS_ERRMISC;
else if (tempclus == DFS_ALLOCNEW) {
tempclus = DFS_GetFreeFAT(volinfo, di->scratch);
if (tempclus == 0x0ffffff7)
return DFS_ERRMISC;
// write out zeroed sectors to the new cluster
memset(di->scratch, 0, SECTOR_SIZE);
for (i=0;i<volinfo->secperclus;i++) {
if (DFS_WriteSector(volinfo->unit, di->scratch, volinfo->dataarea + ((tempclus - 2) * volinfo->secperclus) + i, 1))
return DFS_ERRMISC;
}
// Point old end cluster to newly allocated cluster
i = 0;
DFS_SetFAT(volinfo, di->scratch, &i, di->currentcluster, tempclus);
// Update DIRINFO so caller knows where to place the new file
di->currentcluster = tempclus;
di->currentsector = 0;
di->currententry = 1; // since the code coming after this expects to subtract 1
// Mark newly allocated cluster as end of chain
switch(volinfo->filesystem) {
case FAT12: tempclus = 0xff8; break;
case FAT16: tempclus = 0xfff8; break;
case FAT32: tempclus = 0x0ffffff8; break;
default: return DFS_ERRMISC;
}
DFS_SetFAT(volinfo, di->scratch, &i, di->currentcluster, tempclus);
}
} while (!tempclus);
// We shouldn't get here
return DFS_ERRMISC;
}
/*
Open a file for reading or writing. You supply populated VOLINFO, a path to the file,
mode (DFS_READ or DFS_WRITE) and an empty fileinfo structure. You also need to
provide a pointer to a sector-sized scratch buffer.
Returns various DFS_* error states. If the result is DFS_OK, fileinfo can be used
to access the file from this point on.
*/
uint32_t DFS_OpenFile(PVOLINFO volinfo, uint8_t *path, uint8_t mode, uint8_t *scratch, PFILEINFO fileinfo)
{
uint8_t tmppath[MAX_PATH];
uint8_t filename[12];
uint8_t *p;
DIRINFO di;
DIRENT de;
// larwe 2006-09-16 +1 zero out file structure
memset(fileinfo, 0, sizeof(FILEINFO));
// save access mode
fileinfo->mode = mode;
// Get a local copy of the path. If it's longer than MAX_PATH, abort.
strncpy((char *) tmppath, (char *) path, MAX_PATH);
tmppath[MAX_PATH - 1] = 0;
if (strcmp((char *) path,(char *) tmppath)) {
return DFS_PATHLEN;
}
// strip leading path separators
while (tmppath[0] == DIR_SEPARATOR)
strcpy((char *) tmppath, (char *) tmppath + 1);
// Parse filename off the end of the supplied path
p = tmppath;
while (*(p++));
p--;
while (p > tmppath && *p != DIR_SEPARATOR) // larwe 9/16/06 ">=" to ">" bugfix
p--;
if (*p == DIR_SEPARATOR)
p++;
DFS_CanonicalToDir(filename, p);
if (p > tmppath)
p--;
if (*p == DIR_SEPARATOR || p == tmppath) // larwe 9/16/06 +"|| p == tmppath" bugfix
*p = 0;
// At this point, if our path was MYDIR/MYDIR2/FILE.EXT, filename = "FILE EXT" and
// tmppath = "MYDIR/MYDIR2".
di.scratch = scratch;
if (DFS_OpenDir(volinfo, tmppath, &di))
return DFS_NOTFOUND;
while (!DFS_GetNext(volinfo, &di, &de)) {
if (!memcmp(de.name, filename, 11)) {
// You can't use this function call to open a directory.
if (de.attr & ATTR_DIRECTORY)
return DFS_NOTFOUND;
fileinfo->volinfo = volinfo;
fileinfo->pointer = 0;
// The reason we store this extra info about the file is so that we can
// speedily update the file size, modification date, etc. on a file that is
// opened for writing.
if (di.currentcluster == 0)
fileinfo->dirsector = volinfo->rootdir + di.currentsector;
else
fileinfo->dirsector = volinfo->dataarea + ((di.currentcluster - 2) * volinfo->secperclus) + di.currentsector;
fileinfo->diroffset = di.currententry - 1;
if (volinfo->filesystem == FAT32) {
fileinfo->cluster = (uint32_t) de.startclus_l_l |
((uint32_t) de.startclus_l_h) << 8 |
((uint32_t) de.startclus_h_l) << 16 |
((uint32_t) de.startclus_h_h) << 24;
}
else {
fileinfo->cluster = (uint32_t) de.startclus_l_l |
((uint32_t) de.startclus_l_h) << 8;
}
fileinfo->firstcluster = fileinfo->cluster;
fileinfo->filelen = (uint32_t) de.filesize_0 |
((uint32_t) de.filesize_1) << 8 |
((uint32_t) de.filesize_2) << 16 |
((uint32_t) de.filesize_3) << 24;
return DFS_OK;
}
}
// At this point, we KNOW the file does not exist. If the file was opened
// with write access, we can create it.
if (mode & DFS_WRITE) {
uint32_t cluster, temp;
// Locate or create a directory entry for this file
if (DFS_OK != DFS_GetFreeDirEnt(volinfo, tmppath, &di, &de))
return DFS_ERRMISC;
// put sane values in the directory entry
memset(&de, 0, sizeof(de));
memcpy(de.name, filename, 11);
de.crttime_l = 0x20; // 01:01:00am, Jan 1, 2006.
de.crttime_h = 0x08;
de.crtdate_l = 0x11;
de.crtdate_h = 0x34;
de.lstaccdate_l = 0x11;
de.lstaccdate_h = 0x34;
de.wrttime_l = 0x20;
de.wrttime_h = 0x08;
de.wrtdate_l = 0x11;
de.wrtdate_h = 0x34;
// allocate a starting cluster for the directory entry
cluster = DFS_GetFreeFAT(volinfo, scratch);
de.startclus_l_l = cluster & 0xff;
de.startclus_l_h = (cluster & 0xff00) >> 8;
de.startclus_h_l = (cluster & 0xff0000) >> 16;
de.startclus_h_h = (cluster & 0xff000000) >> 24;
// update FILEINFO for our caller's sake
fileinfo->volinfo = volinfo;
fileinfo->pointer = 0;
// The reason we store this extra info about the file is so that we can
// speedily update the file size, modification date, etc. on a file that is
// opened for writing.
if (di.currentcluster == 0)
fileinfo->dirsector = volinfo->rootdir + di.currentsector;
else
fileinfo->dirsector = volinfo->dataarea + ((di.currentcluster - 2) * volinfo->secperclus) + di.currentsector;
fileinfo->diroffset = di.currententry - 1;
fileinfo->cluster = cluster;
fileinfo->firstcluster = cluster;
fileinfo->filelen = 0;
// write the directory entry
// note that we no longer have the sector containing the directory entry,
// tragically, so we have to re-read it
if (DFS_ReadSector(volinfo->unit, scratch, fileinfo->dirsector, 1))
return DFS_ERRMISC;
memcpy(&(((PDIRENT) scratch)[di.currententry-1]), &de, sizeof(DIRENT));
if (DFS_WriteSector(volinfo->unit, scratch, fileinfo->dirsector, 1))
return DFS_ERRMISC;
// Mark newly allocated cluster as end of chain
switch(volinfo->filesystem) {
case FAT12: cluster = 0xff8; break;
case FAT16: cluster = 0xfff8; break;
case FAT32: cluster = 0x0ffffff8; break;
default: return DFS_ERRMISC;
}
temp = 0;
DFS_SetFAT(volinfo, scratch, &temp, fileinfo->cluster, cluster);
return DFS_OK;
}
return DFS_NOTFOUND;
}
/*
Read an open file
You must supply a prepopulated FILEINFO as provided by DFS_OpenFile, and a
pointer to a SECTOR_SIZE scratch buffer.
Note that returning DFS_EOF is not an error condition. This function updates the
successcount field with the number of bytes actually read.
*/
uint32_t DFS_ReadFile(PFILEINFO fileinfo, uint8_t *scratch, uint8_t *buffer, uint32_t *successcount, uint32_t len)
{
uint32_t remain;
uint32_t result = DFS_OK;
uint32_t sector;
uint32_t bytesread;
// Don't try to read past EOF
if (len > fileinfo->filelen - fileinfo->pointer)
len = fileinfo->filelen - fileinfo->pointer;
remain = len;
*successcount = 0;
while (remain && result == DFS_OK) {
// This is a bit complicated. The sector we want to read is addressed at a cluster
// granularity by the fileinfo->cluster member. The file pointer tells us how many
// extra sectors to add to that number.
sector = fileinfo->volinfo->dataarea +
((fileinfo->cluster - 2) * fileinfo->volinfo->secperclus) +
div(div(fileinfo->pointer,fileinfo->volinfo->secperclus * SECTOR_SIZE).rem, SECTOR_SIZE).quot;
// Case 1 - File pointer is not on a sector boundary
if (div(fileinfo->pointer, SECTOR_SIZE).rem) {
uint16_t tempreadsize;
// We always have to go through scratch in this case
result = DFS_ReadSector(fileinfo->volinfo->unit, scratch, sector, 1);
// This is the number of bytes that we actually care about in the sector
// just read.
tempreadsize = SECTOR_SIZE - (div(fileinfo->pointer, SECTOR_SIZE).rem);
// Case 1A - We want the entire remainder of the sector. After this
// point, all passes through the read loop will be aligned on a sector
// boundary, which allows us to go through the optimal path 2A below.
if (remain >= tempreadsize) {
memcpy(buffer, scratch + (SECTOR_SIZE - tempreadsize), tempreadsize);
bytesread = tempreadsize;
buffer += tempreadsize;
fileinfo->pointer += tempreadsize;
remain -= tempreadsize;
}
// Case 1B - This read concludes the file read operation
else {
memcpy(buffer, scratch + (SECTOR_SIZE - tempreadsize), remain);
buffer += remain;
fileinfo->pointer += remain;
bytesread = remain;
remain = 0;
}
}
// Case 2 - File pointer is on sector boundary
else {
// Case 2A - We have at least one more full sector to read and don't have
// to go through the scratch buffer. You could insert optimizations here to
// read multiple sectors at a time, if you were thus inclined (note that
// the maximum multi-read you could perform is a single cluster, so it would
// be advantageous to have code similar to case 1A above that would round the
// pointer to a cluster boundary the first pass through, so all subsequent
// [large] read requests would be able to go a cluster at a time).
if (remain >= SECTOR_SIZE) {
result = DFS_ReadSector(fileinfo->volinfo->unit, buffer, sector, 1);
remain -= SECTOR_SIZE;
buffer += SECTOR_SIZE;
fileinfo->pointer += SECTOR_SIZE;
bytesread = SECTOR_SIZE;
}
// Case 2B - We are only reading a partial sector
else {
result = DFS_ReadSector(fileinfo->volinfo->unit, scratch, sector, 1);
memcpy(buffer, scratch, remain);
buffer += remain;
fileinfo->pointer += remain;
bytesread = remain;
remain = 0;
}
}
*successcount += bytesread;
// check to see if we stepped over a cluster boundary
if (div(fileinfo->pointer - bytesread, fileinfo->volinfo->secperclus * SECTOR_SIZE).quot !=
div(fileinfo->pointer, fileinfo->volinfo->secperclus * SECTOR_SIZE).quot) {
// An act of minor evil - we use bytesread as a scratch integer, knowing that
// its value is not used after updating *successcount above
bytesread = 0;
if (((fileinfo->volinfo->filesystem == FAT12) && (fileinfo->cluster >= 0xff8)) ||
((fileinfo->volinfo->filesystem == FAT16) && (fileinfo->cluster >= 0xfff8)) ||
((fileinfo->volinfo->filesystem == FAT32) && (fileinfo->cluster >= 0x0ffffff8)))
result = DFS_EOF;
else
fileinfo->cluster = DFS_GetFAT(fileinfo->volinfo, scratch, &bytesread, fileinfo->cluster);
}
}
return result;
}
/*
Seek file pointer to a given position
This function does not return status - refer to the fileinfo->pointer value
to see where the pointer wound up.
Requires a SECTOR_SIZE scratch buffer
*/
void DFS_Seek(PFILEINFO fileinfo, uint32_t offset, uint8_t *scratch)
{
uint32_t tempint;
// larwe 9/16/06 bugfix split case 0a/0b and changed fallthrough handling
// Case 0a - Return immediately for degenerate case
if (offset == fileinfo->pointer) {
return;
}
// Case 0b - Don't allow the user to seek past the end of the file
if (offset > fileinfo->filelen) {
offset = fileinfo->filelen;
// NOTE NO RETURN HERE!
}
// Case 1 - Simple rewind to start
// Note _intentional_ fallthrough from Case 0b above
if (offset == 0) {
fileinfo->cluster = fileinfo->firstcluster;
fileinfo->pointer = 0;
return; // larwe 9/16/06 +1 bugfix
}
// Case 2 - Seeking backwards. Need to reset and seek forwards
else if (offset < fileinfo->pointer) {
fileinfo->cluster = fileinfo->firstcluster;
fileinfo->pointer = 0;
// NOTE NO RETURN HERE!
}
// Case 3 - Seeking forwards
// Note _intentional_ fallthrough from Case 2 above
// Case 3a - Seek size does not cross cluster boundary -
// very simple case
// larwe 9/16/06 changed .rem to .quot in both div calls, bugfix
if (div(fileinfo->pointer, fileinfo->volinfo->secperclus * SECTOR_SIZE).quot ==
div(fileinfo->pointer + offset, fileinfo->volinfo->secperclus * SECTOR_SIZE).quot) {
fileinfo->pointer = offset;
}
// Case 3b - Seeking across cluster boundary(ies)
else {
// round file pointer down to cluster boundary
fileinfo->pointer = div(fileinfo->pointer, fileinfo->volinfo->secperclus * SECTOR_SIZE).quot *
fileinfo->volinfo->secperclus * SECTOR_SIZE;
// seek by clusters
// larwe 9/30/06 bugfix changed .rem to .quot in both div calls
// Lucia 2/4/2023 'fileinfo->pointer + offset' into just 'offset' for bugfix
while (div(fileinfo->pointer, fileinfo->volinfo->secperclus * SECTOR_SIZE).quot !=
div(offset, fileinfo->volinfo->secperclus * SECTOR_SIZE).quot) {
fileinfo->cluster = DFS_GetFAT(fileinfo->volinfo, scratch, &tempint, fileinfo->cluster);
// Abort if there was an error
if (fileinfo->cluster == 0x0ffffff7) {
fileinfo->pointer = 0;
fileinfo->cluster = fileinfo->firstcluster;
return;
}
fileinfo->pointer += SECTOR_SIZE * fileinfo->volinfo->secperclus;
}
// since we know the cluster is right, we have no more work to do
fileinfo->pointer = offset;
}
}
/*
Delete a file
scratch must point to a sector-sized buffer
*/
uint32_t DFS_UnlinkFile(PVOLINFO volinfo, uint8_t *path, uint8_t *scratch)
{
PDIRENT de = (PDIRENT) scratch;
FILEINFO fi;
uint32_t cache = 0;
uint32_t tempclus;
// DFS_OpenFile gives us all the information we need to delete it
if (DFS_OK != DFS_OpenFile(volinfo, path, DFS_READ, scratch, &fi))
return DFS_NOTFOUND;
// First, read the directory sector and delete that entry
if (DFS_ReadSector(volinfo->unit, scratch, fi.dirsector, 1))
return DFS_ERRMISC;
((PDIRENT) scratch)[fi.diroffset].name[0] = 0xe5;
if (DFS_WriteSector(volinfo->unit, scratch, fi.dirsector, 1))
return DFS_ERRMISC;
// Now follow the cluster chain to free the file space
while (!((volinfo->filesystem == FAT12 && fi.firstcluster >= 0x0ff7) ||
(volinfo->filesystem == FAT16 && fi.firstcluster >= 0xfff7) ||
(volinfo->filesystem == FAT32 && fi.firstcluster >= 0x0ffffff7))) {
tempclus = fi.firstcluster;
fi.firstcluster = DFS_GetFAT(volinfo, scratch, &cache, fi.firstcluster);
DFS_SetFAT(volinfo, scratch, &cache, tempclus, 0);
}
return DFS_OK;
}
/*
Write an open file
You must supply a prepopulated FILEINFO as provided by DFS_OpenFile, and a
pointer to a SECTOR_SIZE scratch buffer.
This function updates the successcount field with the number of bytes actually written.
*/
uint32_t DFS_WriteFile(PFILEINFO fileinfo, uint8_t *scratch, uint8_t *buffer, uint32_t *successcount, uint32_t len)
{
uint32_t remain;
uint32_t result = DFS_OK;
uint32_t sector;
uint32_t byteswritten;
// Don't allow writes to a file that's open as readonly
if (!(fileinfo->mode & DFS_WRITE))
return DFS_ERRMISC;
remain = len;
*successcount = 0;
while (remain && result == DFS_OK) {
// This is a bit complicated. The sector we want to read is addressed at a cluster
// granularity by the fileinfo->cluster member. The file pointer tells us how many
// extra sectors to add to that number.
sector = fileinfo->volinfo->dataarea +
((fileinfo->cluster - 2) * fileinfo->volinfo->secperclus) +
div(div(fileinfo->pointer,fileinfo->volinfo->secperclus * SECTOR_SIZE).rem, SECTOR_SIZE).quot;
// Case 1 - File pointer is not on a sector boundary
if (div(fileinfo->pointer, SECTOR_SIZE).rem) {
uint16_t tempsize;
// We always have to go through scratch in this case
result = DFS_ReadSector(fileinfo->volinfo->unit, scratch, sector, 1);
// This is the number of bytes that we don't want to molest in the
// scratch sector just read.
tempsize = div(fileinfo->pointer, SECTOR_SIZE).rem;
// Case 1A - We are writing the entire remainder of the sector. After
// this point, all passes through the read loop will be aligned on a
// sector boundary, which allows us to go through the optimal path
// 2A below.
if (remain >= SECTOR_SIZE - tempsize) {
memcpy(scratch + tempsize, buffer, SECTOR_SIZE - tempsize);
if (!result)
result = DFS_WriteSector(fileinfo->volinfo->unit, scratch, sector, 1);
byteswritten = SECTOR_SIZE - tempsize;
buffer += SECTOR_SIZE - tempsize;
fileinfo->pointer += SECTOR_SIZE - tempsize;
if (fileinfo->filelen < fileinfo->pointer) {
fileinfo->filelen = fileinfo->pointer;
}
remain -= SECTOR_SIZE - tempsize;
}
// Case 1B - This concludes the file write operation
else {
memcpy(scratch + tempsize, buffer, remain);
if (!result)
result = DFS_WriteSector(fileinfo->volinfo->unit, scratch, sector, 1);
buffer += remain;
fileinfo->pointer += remain;
if (fileinfo->filelen < fileinfo->pointer) {
fileinfo->filelen = fileinfo->pointer;
}
byteswritten = remain;
remain = 0;
}
} // case 1
// Case 2 - File pointer is on sector boundary
else {
// Case 2A - We have at least one more full sector to write and don't have
// to go through the scratch buffer. You could insert optimizations here to
// write multiple sectors at a time, if you were thus inclined. Refer to
// similar notes in DFS_ReadFile.
if (remain >= SECTOR_SIZE) {
result = DFS_WriteSector(fileinfo->volinfo->unit, buffer, sector, 1);
remain -= SECTOR_SIZE;
buffer += SECTOR_SIZE;
fileinfo->pointer += SECTOR_SIZE;
if (fileinfo->filelen < fileinfo->pointer) {
fileinfo->filelen = fileinfo->pointer;
}
byteswritten = SECTOR_SIZE;
}
// Case 2B - We are only writing a partial sector and potentially need to
// go through the scratch buffer.
else {
// If the current file pointer is not yet at or beyond the file
// length, we are writing somewhere in the middle of the file and
// need to load the original sector to do a read-modify-write.
if (fileinfo->pointer < fileinfo->filelen) {
result = DFS_ReadSector(fileinfo->volinfo->unit, scratch, sector, 1);
if (!result) {
memcpy(scratch, buffer, remain);
result = DFS_WriteSector(fileinfo->volinfo->unit, scratch, sector, 1);
}
}
else {
result = DFS_WriteSector(fileinfo->volinfo->unit, buffer, sector, 1);
}
buffer += remain;
fileinfo->pointer += remain;
if (fileinfo->filelen < fileinfo->pointer) {
fileinfo->filelen = fileinfo->pointer;
}
byteswritten = remain;
remain = 0;
}
}
*successcount += byteswritten;
// check to see if we stepped over a cluster boundary
if (div(fileinfo->pointer - byteswritten, fileinfo->volinfo->secperclus * SECTOR_SIZE).quot !=
div(fileinfo->pointer, fileinfo->volinfo->secperclus * SECTOR_SIZE).quot) {
uint32_t lastcluster;
// We've transgressed into another cluster. If we were already at EOF,
// we need to allocate a new cluster.
// An act of minor evil - we use byteswritten as a scratch integer, knowing
// that its value is not used after updating *successcount above
byteswritten = 0;
lastcluster = fileinfo->cluster;
fileinfo->cluster = DFS_GetFAT(fileinfo->volinfo, scratch, &byteswritten, fileinfo->cluster);
// Allocate a new cluster?
if (((fileinfo->volinfo->filesystem == FAT12) && (fileinfo->cluster >= 0xff8)) ||
((fileinfo->volinfo->filesystem == FAT16) && (fileinfo->cluster >= 0xfff8)) ||
((fileinfo->volinfo->filesystem == FAT32) && (fileinfo->cluster >= 0x0ffffff8))) {
uint32_t tempclus;
tempclus = DFS_GetFreeFAT(fileinfo->volinfo, scratch);
byteswritten = 0; // invalidate cache
if (tempclus == 0x0ffffff7)
return DFS_ERRMISC;
// Link new cluster onto file
DFS_SetFAT(fileinfo->volinfo, scratch, &byteswritten, lastcluster, tempclus);
fileinfo->cluster = tempclus;
// Mark newly allocated cluster as end of chain
switch(fileinfo->volinfo->filesystem) {
case FAT12: tempclus = 0xff8; break;
case FAT16: tempclus = 0xfff8; break;
case FAT32: tempclus = 0x0ffffff8; break;
default: return DFS_ERRMISC;
}
DFS_SetFAT(fileinfo->volinfo, scratch, &byteswritten, fileinfo->cluster, tempclus);
result = DFS_OK;
}
// No else clause is required.
}
}
// Update directory entry
if (DFS_ReadSector(fileinfo->volinfo->unit, scratch, fileinfo->dirsector, 1))
return DFS_ERRMISC;
((PDIRENT) scratch)[fileinfo->diroffset].filesize_0 = fileinfo->filelen & 0xff;
((PDIRENT) scratch)[fileinfo->diroffset].filesize_1 = (fileinfo->filelen & 0xff00) >> 8;
((PDIRENT) scratch)[fileinfo->diroffset].filesize_2 = (fileinfo->filelen & 0xff0000) >> 16;
((PDIRENT) scratch)[fileinfo->diroffset].filesize_3 = (fileinfo->filelen & 0xff000000) >> 24;
if (DFS_WriteSector(fileinfo->volinfo->unit, scratch, fileinfo->dirsector, 1))
return DFS_ERRMISC;
return result;
}
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