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kolibrios/kernel/trunk/bootloader/extended_primary_loader/after_win/fat.inc
CleverMouse 037099f50d Style corrected for new rules, no semantic changes 
git-svn-id: svn://kolibrios.org@2288 a494cfbc-eb01-0410-851d-a64ba20cac60
2011-10-14 21:38:50 +00:00

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; Copyright (c) 2008-2009, diamond
; All rights reserved.
;
; Redistribution and use in source and binary forms, with or without
; modification, are permitted provided that the following conditions are met:
; * Redistributions of source code must retain the above copyright
; notice, this list of conditions and the following disclaimer.
; * Redistributions in binary form must reproduce the above copyright
; notice, this list of conditions and the following disclaimer in the
; documentation and/or other materials provided with the distribution.
; * Neither the name of the <organization> nor the
; names of its contributors may be used to endorse or promote products
; derived from this software without specific prior written permission.
;
; THIS SOFTWARE IS PROVIDED BY Alexey Teplov aka <Lrz> ''AS IS'' AND ANY
; EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
; WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
; DISCLAIMED. IN NO EVENT SHALL <copyright holder> BE LIABLE FOR ANY
; DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
; (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
; ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
; (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
; SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
;*****************************************************************************
; in: ss:bp = 0:dat
; in: es:bx = address to load file
; in: ds:si -> ASCIIZ name
; in: cx = limit in sectors
; out: bx = status: bx=0 - ok, bx=1 - file is too big, only part of file has been loaded, bx=2 - file not found
; out: dx:ax = file size (0xFFFFFFFF if file not found)
load_file_fat:
mov eax, [bp + root_clus - dat]
mov [bp + cur_obj - dat], root_string
push es
push bx
push cx
.parse_dir_loop:
; convert name to FAT name
push [bp + cur_obj - dat]
push ax
mov [bp + cur_obj - dat], si
push ss
pop es
; convert ASCIIZ filename to FAT name
mov di, fat_filename
push di
mov cx, 8+3
mov al, ' '
rep stosb
pop di
mov cl, 8 ; 8 symbols per name
mov bl, 1
.nameloop:
lodsb
test al, al
jz .namedone
cmp al, '/'
jz .namedone
cmp al, '.'
jz .namedot
dec cx
js .badname
cmp al, 'a'
jb @f
cmp al, 'z'
ja @f
sub al, 'a'-'A'
@@:
stosb
jmp .nameloop
.namedot:
inc bx
jp .badname
add di, cx
mov cl, 3
jmp .nameloop
.badname:
mov si, badname_msg
jmp find_error_si
.namedone:
; scan directory
pop ax ; eax = cluster of directory
; high word of eax is preserved by operations above
push ds
push si
; read a folder sector-by-sector and scan
; first, try to use the cache
push ss
pop ds
mov bx, -2
mov cx, [bp + rootcache_size - dat]
cmp [bp + root_clus - dat], eax
jz .lookcache_root
mov di, foldcache_mark
xor bx, bx
mov cx, [bp + cachelimit - dat]
@@:
lea si, [di+bx]
mov edx, dword [foldcache_clus+si-foldcache_mark+bx]
cmp edx, eax
jz .cacheok
test edx, edx
jz .cacheadd ; the cache has place for new entry
inc bx
inc bx
dec cx
js @b
; the folder is not present in the cache, so add it
; the cache is full; find the oldest entry and replace it with the new one
mov bx, -2
mov dx, [bp + cachelimit - dat]
@@:
inc bx
inc bx
cmp word [di+bx], dx ; marks have values 0 through [cachelimit]
jnz @b
.cacheadd:
or word [di+bx], 0xFFFF ; very big value, it will be changed soon
and [foldcache_size+di-foldcache_mark+bx], 0 ; no folder items yet
lea si, [di+bx]
mov dword [foldcache_clus+si-foldcache_mark+bx], eax
.cacheok:
; update cache marks
mov dx, [di+bx]
mov cx, [foldcache_size+di-foldcache_mark+bx]
mov di, [bp + cachelimit - dat]
add di, di
.cacheupdate:
cmp [foldcache_mark+di], dx
adc [foldcache_mark+di], 0
dec di
dec di
jns .cacheupdate
and [foldcache_mark+bx], 0
; done, bx contains (position in cache)*2
.lookcache_root:
; bx = (position in cache)*2 for non-root folders; bx = -2 for root folder
;mov dx, bx
;shl dx, 8
;add dx, 0x9200
lea dx, [bx + 0x92]
xchg dl, dh
mov ds, dx
mov si, fat_filename ; ss:si -> filename in FAT style
call fat_scan_for_filename
jz .lookup_done
; cache miss, read folder data from disk
; we are reading parent directory, it can result in disk read errors; restore [cur_obj]
mov di, sp
mov bx, [bp + cur_obj - dat]
xchg bx, [ss:di+4]
mov [bp + cur_obj - dat], bx
mov bx, cx
add bx, 0xF
shr bx, 4
shl cx, 5
mov di, cx ; es:di -> free space in cache entry
; external loop: scan clusters
.folder_next_cluster:
; internal loop: scan sectors in cluster
movzx ecx, byte [ss:0x320D] ; BPB_SecPerClus
push eax
; FAT12/16 root - special handling
test eax, eax
jnz .folder_notroot
mov cx, [ss:0x3211] ; BPB_RootEntCnt
mov dx, cx
add cx, 0xF
rcr cx, 1
shr cx, 3
mov eax, [bp + root_start - dat]
jmp .folder_next_sector
.folder_notroot:
mul ecx
add eax, [bp + data_start - dat]
.folder_next_sector:
sub dx, 0x10
; skip first bx sectors
dec bx
jns .folder_skip_sector
push cx
push es di
push 0x8000
pop es
xor bx, bx
mov cx, 1
push es
call read
jc ..found_disk_error
; copy data to the cache...
pop ds
pop di es
cmp di, 0x2000 ; ...if there is free space, of course
jae @f
pusha
mov cx, 0x100
xor si, si
rep movsw
mov di, es
shr di, 8
cmp di, 0x90
jz .update_rootcache_size
add [ss:foldcache_size+di-0x92], 0x10 ; 0x10 new entries in the cache
jmp .updated_cachesize
.update_rootcache_size:
mov cl, 0x10
cmp cx, dx
jb @f
mov cx, dx
@@:
add [bp + rootcache_size - dat], cx
.updated_cachesize:
popa
@@:
push es
mov cl, 0x10 ; ch=0 at this point
cmp cx, dx
jb @f
mov cx, dx
@@:
call fat_scan_for_filename
pop es
pop cx
jz .lookup_done_pop
.folder_skip_sector:
inc eax
loop .folder_next_sector
pop eax ; eax = current cluster
test eax, eax
jz @f
call [bp + get_next_cluster_ptr - dat]
jc .folder_next_cluster
@@:
stc
push eax
.lookup_done_pop:
pop eax
.lookup_done:
pop si
; CF=1 <=> failed
jnc .found
pop ds
pop [bp + cur_obj - dat]
mov si, error_not_found
jmp find_error_si
.found:
mov eax, [di+20-2]
mov edx, [di+28]
mov ax, [di+26] ; get cluster
test byte [di+11], 10h ; directory?
pop ds
pop [bp + cur_obj - dat] ; forget old [cur_obj]
jz .regular_file
cmp byte [si-1], 0
jnz .parse_dir_loop
..directory_error:
mov si, directory_string
jmp find_error_si
.regular_file:
cmp byte [si-1], 0
jz @f
..notdir_error:
mov si, notdir_string
jmp find_error_si
@@:
; ok, we have found a regular file and the caller requested it
; parse FAT chunk
push ss
pop es
push ss
pop ds
mov di, 0x4005
mov byte [di-5], 1 ; non-resident attribute
mov dword [di-4], 1
stosd
pop cx
push cx
.parsefat:
call [bp + get_next_cluster_ptr - dat]
jnc .done
mov esi, [di-8]
add esi, [di-4]
cmp eax, esi
jz .contc
mov dword [di], 1
scasd
stosd
jmp @f
.contc:
inc dword [di-8]
@@:
sub cl, [0x320D]
sbb ch, 0
ja .parsefat
.done:
xor eax, eax
stosd
mov si, 0x4000
load_file_common_end:
xor ecx, ecx
pop cx
pop bx
pop es
mov [bp + filesize - dat], edx
mov [bp + sectors_read - dat], ecx
add edx, 0x1FF
shr edx, 9
mov [bp + filesize_sectors - dat], edx
cmp edx, ecx
seta al
mov ah, 0
push ax
call read_file_chunk
continue_load_common_end:
mov [bp + cur_chunk_ptr - dat], si
pop bx
mov ax, word [bp + filesize - dat]
mov dx, word [bp + filesize+2 - dat]
jnc @f
mov bl, 3 ; read error
@@:
ret
continue_load_file:
; es:bx -> buffer for output, ecx = cx = number of sectors
mov si, [bp + cur_chunk_ptr - dat]
push ecx
add ecx, [bp + sectors_read - dat]
mov [bp + sectors_read - dat], ecx
cmp [bp + filesize_sectors - dat], ecx
pop ecx
seta al
mov ah, 0
push ax
push continue_load_common_end
push ss
pop ds
cmp [bp + cur_chunk_resident - dat], ah
jnz .nonresident
.resident:
mov ax, word [bp + num_sectors - dat]
jmp read_file_chunk.resident.continue
.nonresident:
mov eax, [bp + cur_cluster - dat]
mov edx, [bp + num_sectors - dat]
add eax, [bp + cur_delta - dat]
jmp read_file_chunk.nonresident.continue
fat_scan_for_filename:
; in: ss:si -> 11-bytes FAT name
; in: ds:0 -> part of directory data
; in: cx = number of entries
; out: if found: CF=0, ZF=1, es:di -> directory entry
; out: if not found, but continue required: CF=1 and ZF=0
; out: if not found and zero item reached: CF=1 and ZF=1
push ds
pop es
xor di, di
push cx
jcxz .noent
.loop:
cmp byte [di], 0
jz .notfound
test byte [di+11], 8 ; volume label?
jnz .cont ; ignore volume labels
pusha
mov cx, 11
repz cmps byte [ss:si], byte [es:di]
popa
jz .done
.cont:
add di, 0x20
loop .loop
.noent:
inc cx ; clear ZF flag
.notfound:
stc
.done:
pop cx
ret
fat12_get_next_cluster:
; in: ax = cluster (high word of eax is zero)
; out: if there is next cluster: CF=1, ax = next cluster
; out: if there is no next cluster: CF=0
push si
push ds
push 0x6000
pop ds
mov si, ax
shr si, 1
add si, ax
test al, 1
lodsw
jz @f
shr ax, 4
@@:
and ax, 0xFFF
cmp ax, 0xFF7
pop ds si
ret
fat16_get_next_cluster:
; in: ax = cluster (high word of eax is zero)
; out: if there is next cluster: CF=1, ax = next cluster
; out: if there is no next cluster: CF=0
; each sector contains 200h bytes = 100h FAT entries
; so ah = # of sector, al = offset in sector
push si
mov si, ax
shr si, 8
; calculate segment for this sector of FAT table
; base for FAT table is 6000:0000, so the sector #si has to be loaded to (60000 + 200*si)
; segment = 6000 + 20*si, offset = 0
push es
push si
shl si, 5
add si, 0x6000
mov es, si
pop si
cmp byte [ss:0x3400+si], 0 ; sector already loaded?
jnz .noread
; load corresponding sector, try all FATs if disk read error detected
pusha
movzx di, byte [ss:0x3210] ; BPB_NumFATs
xor bx, bx
mov ax, [ss:0x320E] ; BPB_RsvdSecCnt
xor dx, dx
add ax, si
adc dx, bx
@@:
push es
push dx ax
pop eax
mov cx, 1 ; read 1 sector
call read
pop es
jnc @f
add ax, [ss:0x3216] ; BPB_FATSz16
adc dx, bx
dec di
jnz @b
..found_disk_error:
mov si, disk_error_msg
jmp find_error_si
@@:
popa
.noread:
mov si, ax
and si, 0xFF
add si, si
mov ax, [es:si]
pop es
cmp ax, 0xFFF7
pop si
ret
fat32_get_next_cluster:
; in: eax = cluster
; out: if there is next cluster: CF=1, eax = next cluster
; out: if there is no next cluster: CF=0
push di
push ax
shr eax, 7
; eax = FAT sector number; look in cache
push si
mov si, cache1head
call cache_lookup
pop si
jnc .noread
; read FAT, try all FATs if disk read error detected
push es
pushad
movzx edx, word [ss:0x320E] ; BPB_RsvdSecCnt
add eax, edx
movzx si, byte [ss:0x3210] ; BPB_NumFATs
@@:
lea cx, [di - 0x3400 + (0x6000 shr (9-3))]
shl cx, 9-3
mov es, cx
xor bx, bx
mov cx, 1
call read
jnc @f
add eax, [ss:0x3224] ; BPB_FATSz32
dec si
jnz @b
jmp ..found_disk_error
@@:
popad
pop es
.noread:
; get requested item
lea ax, [di - 0x3400 + (0x6000 shr (9-3))]
pop di
and di, 0x7F
shl di, 2
shl ax, 9-3
push ds
mov ds, ax
and byte [di+3], 0x0F
mov eax, [di]
pop ds
pop di
;and eax, 0x0FFFFFFF
cmp eax, 0x0FFFFFF7
ret
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