fat12 structures, constants and general framework done

[BOS.git] / kernel / fat12 / fat12.asm

diff --git a/kernel/fat12/fat12.asm b/kernel/fat12/fat12.asm
index 0b87c662ac429bc8c56b9596fef857f546482251..a96178245aba6e52c2d00cc61c1c300f730e0705 100644 (file)
--- a/kernel/fat12/fat12.asm
+++ b/kernel/fat12/fat12.asm
@@ -5,58 +5,235 @@
 ;    FAT12 driver.                                         ;
 ;                                                          ;
 ;----------------------------------------------------------;
 ;    FAT12 driver.                                         ;
 ;                                                          ;
 ;----------------------------------------------------------;

-      struc disk
-      {
-          .disk_number         db  0                  ; which disk?
-          .root_dir            dw  0                  ; position of rootdir
-          .fat_1               dd  0                  ; position of fat1
-          .fat_2               dd  0                  ; position of fat2
-          .data_area           dw  0                  ; position of dataarea
-          .disk_size           dd  0
-          .free_space          dd  0
-          .boot                bootsector  
-          ; ..... some other values
-      }
-      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  
-          ;.... more values here
-      }
-
-      virtual at 0
-          bootsector bootsector
-          sizeof.bootsector = $
-      end virtual
-
-      virtual at 0
-          disk disk 
-          sizeof.disk = $     
-      end virtual
-
-
-fd0 disk            ; define fd0 data..  
-
-;drv dd 0
-;mov edi, drv+disk.boot

 
 

-     ;-----------------------------; 
-     ;   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  
+    ;---------------------------------------------;
+    ;   main FAT12 info structure                 ;
+    ;---------------------------------------------;
+    struc fat12
+    {
+        .disk_number                     db  0       ; which VFS disk number
+        .root_dir                        dw  0       ; position of rootdir
+        .fat_1                           dd  0       ; position of fat1
+        .fat_2                           dd  0       ; position of fat2
+        .data_area                       dw  0       ; position of dataarea
+        .disk_size                       dd  0       ; total storage size
+        .free_space                      dd  0       ; free space available
+        .boot                            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           
+    }
+
+    ;---------------------------------------------;
+    ;   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
+    }
+
+    ;---------------------------------------------;
+    ;   FAT12 directory entry structure           ;
+    ;---------------------------------------------;
+    struct 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
+    }
+
+    ;---------------------------------------------;
+    ;   FAT12 directory entry for LFN             ;
+    ;---------------------------------------------;
+    struct lnf_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
+
+    virtual at 0
+        dir_entry dir_entry
+        sizeof.dir_entry = $
+    end virtual
+
+    virtual at 0
+        bootsector bootsector
+        sizeof.bootsector = $
+    end virtual
+
+    virtual at 0
+        disk disk 
+        sizeof.disk = $     
+    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
+

 
 

-;mov  si, [dsk] 
-;mov  ax, [si+disk.boot.sectorssize] 

 
 
 
 

+
+fd0: fat12            ; define fd0 data..  tmp example.
+
+; TODO, alloc memory for struct and keep pointer only.
+; ---------------
+;drive dd 0
+;mov edi, drive+fat12into.boot
+
+;--------------------------------------------------------------;
+;   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
 init_fat12:
         push   eax

+        ;...
+
+     ;-----------------------------; 
+     ;   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
         ; 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:
+        add    ax, byte [esi]                         ; add next char to sum
+        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
         ret
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