; ;
;----------------------------------------------------------;
+ ;---------------------------------------------;
+ ; FAT12 calltable and structure pointer ;
+ ;---------------------------------------------;
+ FAT12:
+ .data_pointer dd 0 ; internal driver data
+ .FSname db 'FAT12' ; 5 char filesystem name
+ .init dd init_fat12 ; pointer to init
+ .deinit dd 0 ; remove driver
+ .format dd 0 ; format drive
+ .mount dd 0 ; mount drive
+ .unmount dd 0 ; unmount drive
+ .find dd 0 ; find file
+ .findnext dd 0 ; get next match
+ .open dd 0 ; open file, get handle
+ .close dd 0 ; close file from handle
+ .attrib dd 0 ; get/set attrib. and time
+ .read dd 0 ; read file from handle
+ .write dd 0 ; write file from handle
+ .seek dd 0 ; seek from handle
+ .rename dd 0 ; rename file
+ .remove dd 0 ; remove file/dir
+ .create dd 0 ; create file/dir
+ .ioctl dd 0 ; extra calls if exists
+
+ ;---------------------------------------------;
+ ; FAT12 main info structure ;
+ ;---------------------------------------------;
+ struc fat12_data
+ {
+ .disk_number db 0 ; which VFS disk number
+ .root_dir dw 0 ; position of rootdir
+ .disk_size dd 0 ; total storage size
+ .free_space dd 0 ; free space available
+ .fat_1 dd 0 ; position of fat1
+ .fat_2 dd 0 ; position of fat2
+ .data_area dw 0 ; position of dataarea
+ .boot: times sizeof.bootsector db 0 ; copy of FAT12 bootsector
+ .dir_entries:
+ times 16 * sizeof.dir_entry db 0 ; 512b dir entry buffer
+ .fat_buffer: times 512 db 0 ; 512b FAT cluster info buffer
+ .foundfile:
+ times 1 * sizeof.search db 0 ; "DTA" like structure
+ .filehandles: ; "System File Table"
+ times 32 * sizeof.filehandle db 0 ; for now, max opened files is 32
+ }
+
+ virtual at 0 ; could use "at esi" instead
+ fat12_data fat12_data
+ sizeof.fat12_data = $-$$
+ end virtual
+
+ ;---------------------------------------------;
+ ; FAT12 bootsector structure ;
+ ;---------------------------------------------;
+ struc bootsector ; 512 bytes
+ {
+ .jumper db 0,0,0
+ .oem db 0,0,0,0,0,0,0,0
+ .sectorsize dw 0
+ .sect_per_clust db 0
+ .reserved_sect dw 0 ; reserved sectors, 1 for bootsector.
+ .fats_per_drive db 0
+ .root_entries dw 0
+ .small_sectors dw 0 ; total sectors on small disk
+ .media_describtor db 0 ; 240 / 0xF0 = 1.44MB, 3.5"
+ .sectors_per_fat dw 0 ; 9 on 1.44MB, 3,5"
+ .sect_per_track dw 0 ; 18 on 1.44MB, 3,5"
+ .heads dw 0 ; 2 on 1.44MB, 3,5"
+ .hidden_sectors dd 0 ; sectors before bootsector
+ .large_sectors dd 0 ; total sectors if large disk
+ .drive_no db 0
+ .reserved_field db 0
+ .bpb_signature db 0 ; 41=3 more (win NT req.), 0=end.
+ .disk_id dd 0 ; random ident number on format.
+ .volume_label db 0,0,0,0,0,0,0,0,0,0,0
+ .filesystem db 0,0,0,0,0,0,0,0 ; "FAT12 " or "FAT16 "
+ .code: times 448 db 0
+ .boot_signature db 0,0 ; 0x55,0xAA
+ }
+
+ virtual at 0
+ bootsector bootsector
+ sizeof.bootsector = $-$$
+ end virtual
+
+ ;---------------------------------------------;
+ ; FAT12 directory entry structure ;
+ ;---------------------------------------------;
+ struc dir_entry
+ {
+ .filename db 0,0,0,0,0,0,0,0
+ .extension db 0,0,0
+ .attributes db 0 ; 0x10 = dir for example.
+ .reserved db 0,0,0,0,0,0,0,0,0,0
+ .changed_time dw 0
+ .changed_date dw 0
+ .start_cluster dw 0
+ .filesize dd 0
+ }
+
+ virtual at 0
+ dir_entry dir_entry
+ sizeof.dir_entry = $-$$
+ end virtual
+
+ ;---------------------------------------------;
+ ; FAT12 directory entry for LFN ;
+ ;---------------------------------------------;
+ struc lfn_entry
+ {
+ .order db 0 ; LFN entry in sequence, never 0x00 or 0xE5.
+ .namefirst dw 0,0,0,0,0 ; 5 first unicode (2byte) chars
+ .attribute db 0 ; 0x0F for Long File Name identification.
+ .reserved db 0
+ .checksum db 0 ; 8.3 name checksum
+ .namemiddle dw 0,0,0,0,0,0 ; middle 6 unicode (2byte) chars
+ .zero_cluster dw 0 ; always zero on LNF entries
+ .namelast dw 0,0 ; last 2 unicode (2byte) characters.
+ }
+
+ virtual at 0
+ lfn_entry lfn_entry
+ sizeof.lfn_entry = $-$$
+ end virtual
+
+ ;---------------------------------------------;
+ ; FAT12 file search/DTA structure ;
+ ;---------------------------------------------;
+ struc search
+ {
+ .searchname:
+ times 255 db 0 ; file search pattern.
+ .attribute db 0 ; search attribute.
+ .direntry dw 0 ; directory entry number, 0 based
+ .dircluster dw 0 ; starting cluster of dir, 0 root
+ .foundattrib db 0 ; attribute of matching file
+ .foundtime dw 0 ; file time
+ .founddate dw 0 ; file date
+ .foundsize dw 0 ; file size
+ }
+
+ virtual at 0
+ search search
+ sizeof.search = $-$$
+ end virtual
+
+ ;---------------------------------------------;
+ ; FAT12 file-handle structure ;
+ ;---------------------------------------------;
+ struc filehandle
+ {
+ .handles db 0 ; reference count or or zero for unused
+ .mode db 0 ; open mode. 0=read, 1=write, 2=r/w.
+ .lfn_entry dw 0 ; file LFN directory entry position
+ .direntry dw 0 ; file directory entry position
+ .cluster dw 0 ; file first cluster
+ .attribute db 0 ; file attributes
+ .filetime dw 0 ; last modified time
+ .filedate dw 0 ; last modified date
+ .filesize dd 0 ; filesize
+ .position dd 0 ; R/W position in file
+ .clusterpos dw 0 ; cluster number of last cluster read
+ .shortname:
+ times 11 db 0 ; short name
+ .fullname:
+ times 255 db 0 ; the full LFN
+ }
+
+ virtual at 0
+ filehandle filehandle
+ sizeof.filehandle = $-$$
+ end virtual
+
+ ;------------------------------------------;
+ ; FAT cluster constants used ;
+ ;------------------------------------------;
+ cluster_free = 0x000 ; up for grabs.
+ cluster_reserved = 0xFF0 ; 0xFF0-0xFF6. 0xFF7=bad.
+ cluster_last = 0xFF8 ; 0xFF8-0xFFF last cluster.
+
+ ;------------------------------------------;
+ ; Directory entry first char constants ;
+ ;------------------------------------------;
+ entry_free = 0xE5 ; up for grabs.
+ entry_last = 0x00 ; this and remaining is free
+ entry_japan_kludge = 0x0E ; should be outputed as 0xE5.
+ entry_dot = 0x2E ; ASCII dot, check for "." or ".." dirs
+
+ ;------------------------------------------;
+ ; Directory entry attribute masks ;
+ ;------------------------------------------;
+ mask_readonly = 0x01
+ mask_hidden = 0x02
+ mask_system = 0x04
+ mask_volume_label = 0x08
+ mask_subdirectory = 0x10
+ mask_archive = 0x20
+
+ ;------------------------------------------;
+ ; Long File Name entry constants ;
+ ;------------------------------------------;
+ lfn_last_entry_mask = 0x40 ; LFN sequence-order mask for last
+ attribute_lfn = 0x0F ; attrb. byte value for LFN dir entry
+
+
+;--------------------------------------------------------------;
+; init_fat12 - detect if drive fs is fat12 and init ;
+;--------------------------------------------------------------;
+; ;
+; in: reg = pointer to VFS drive info ;
+; ;
+; out: reg = pointer to struct(s) if FAT12 found ;
+; ;
+;--------------------------------------------------------------;
init_fat12:
push eax
- ; a bit more code here
+ ;...
+
+ ;-----------------------------;
+ ; calculate root location ;
+ ;-----------------------------;
+ xor eax, eax
+ mov al, byte [fd0.boot.fats_per_drive]
+ mul word [fd0.boot.sectors_per_fat]
+ add ax, word [fd0.boot.reserved_sect]
+ mov [fd0.root_dir], ax
+
+; working with
+;mov si, [drive]
+;mov ax, [si+fat12.boot.sectorssize]
+
+ ; a bit more code here
pop eax
+ ret
+
+;--------------------------------------------------------------;
+; calc_lfn_chksum - get long file name checksum ;
+;--------------------------------------------------------------;
+; ;
+; in: esi = pointer to 11 byte 8.3 filename ;
+; ;
+; out: ax = checksum ;
+; ;
+;--------------------------------------------------------------;
+calc_lfn_chksum:
+ push cx
+ push esi
+
+ mov cx, 11
+ xor ax, ax ; return value start with null
+ .l1:
+ push cx
+ movzx cx, byte [esi] ; add next char to sum
+ add ax, cx
+ pop cx
+ shr ax, 1 ; shift sum right by 1
+ inc esi ; prepare for next character
+ loop .l1
+
+ pop esi
+ pop cx
+ ret
+
+;--------------------------------------------------------------;
+; get_dir_entry - get a directory entry or amount ;
+;--------------------------------------------------------------;
+; ;
+; in: esi = pointer to prev dir entry or 0 for root ;
+; cx = entry no. to extract or 0 for none ;
+; ;
+; out: cx = number of entries or unchanged if set ;
+; edi = pointer to dir entry or unchanged if cx=0 ;
+;--------------------------------------------------------------;
+get_dir_entry:
+ ;......
+ ret
+
+;--------------------------------------------------------------;
+; get_fat_entry - get a fat entry/cluster number ;
+;--------------------------------------------------------------;
+; ;
+; in: cx = fat entry/cluster number ;
+; ;
+; out: cx = next fat entry/cluster no. or 0 if none ;
+;--------------------------------------------------------------;
+get_fat_entry:
+ ;...
+ ret
+
+;--------------------------------------------------------------;
+; get_cluster - get a cluster ;
+;--------------------------------------------------------------;
+; ;
+; in: cx = fat entry/cluster number ;
+; ;
+; out: edi = pointer to cluster or zero if none ;
+;--------------------------------------------------------------;
+get_cluster:
+ ;...
ret
\ No newline at end of file
projects / BOS.git / blobdiff