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Assembly Source File | 1992-05-26 | 35KB | 1,296 lines

;==================================================================== ; REDD - Remote Exec Device Driver ; ; Copyright (c) 1992 Douglas Boling ;==================================================================== page 66,132 ;-------------------------------------------------------------------- ; BIOS Data segment ;-------------------------------------------------------------------- bios_data segment at 40h org 17h shift_state db ? ;State of shift keys org 1Ah keybuff_head dw ? ;Start ptr for key buff keybuff_tail dw ? ;End ptr for key buff org 4Eh video_buffoff dw ? ;Offset of video buffer org 63h video_ioregs dw ? ;I/O addr of video ctlr org 80h keybuff_start dw ? ;Start ptr for keybuff keybuff_end dw ? ;End ptr for keybuff video_rows db ? ;Screen rows bios_data ends ;-------------------------------------------------------------------- ; CODE segment ;-------------------------------------------------------------------- code segment assume cs:code generic_req struc Len db ? ;Size of structure Unit db ? Function db ? ;Requested function Status dw ? ;Returned status Reserved db 8 dup (?) generic_req ends init_req struc irLen db ? ;Size of structure irUnit db ? irFunction db ? ;Requested function irStatus dw ? ;Returned status irReserved db 8 dup (?) irUnits db ? ;Number of block drives irEndAddress dd ? ;End addr of driver irParmAddress dd ? ;Ptr to cmd line parms irDriveNumber db ? ;1st drive number irMessageflag dw ? ;Error word init_req ends media_req struc mrLen db ? ;Size of structure mrUnit db ? mrFunction db ? ;Requested function mrStatus dw ? ;Returned status mrReserved db 8 dup (?) mrMediaID db ? ;Media descripter mrReturn db ? ;return value mrVolumeID dd ? ;Ptr to volumne ID string media_req ends buildbpb_req struc bbrLen db ? ;Size of structure bbrUnit db ? bbrFunction db ? ;Requested function bbrStatus dw ? ;Returned status bbrReserved db 8 dup (?) bbrMediaID db ? ;Media descripter bbrFATSector dd ? ;Ptr to 1st FAT sector bbrBPBAddress dd ? ;Ptr to BPB block buildbpb_req ends read_req struc rrLen db ? ;Size of structure rrUnit db ? rrFunction db ? ;Requested function rrStatus dw ? ;Returned status rrReserved db 8 dup (?) rrMediaID db ? ;Media descripter rrBuffer dd ? ;Ptr to data buffer rrBytesSec dw ? ;Number of sectors to read rrStartSec dw ? ;Starting sector number rrVolumeID dd ? ;Ptr to volume ID string rrHugeStartSec dd ? ;Start sec for >32 Meg drive read_req ends ;==================================================================== ;Device driver header ;==================================================================== org 0 ;Offset 0 for DD header dd -1 ;Ptr to next driver dw 0800h ;Attribute word bits ;15 Character device ;14 IOCTL read/write support ;13 (Char) Output till busy ; (Blk) Needs FAT for BPB ;11 Open/Close dev supported ; 7 IOCTL querys supported ; 6 Log drive mapping support ; 4 Fast char input support ; 3 Device is clock device ; 2 Device is NULL device ; 1 (Char) Std out device ; (Blk) 32 bit sector nums ; 0 Device is Std Input dev dw offset strategy ;Ptr to strategy routine dw offset interrupt ;Ptr to interrupt routine db 1,0,0,0,0,0,0,0 ;Num of block devices program db 10,13,"REDD",10,13 db "Copyright (c) 1992 Douglas Boling",13,10 db "First published in PC Magazine, September 15, 1992" db 13,10,"$",1Ah ;-------------------------------------------------------------------- ;Boot Sector data for our imaginary drive ;-------------------------------------------------------------------- boot_sector = $ jmp short boot_sector_end ;obligitory jmp instruction nop db "IBM x.x " ;Stupid IBM tag for DOS 4 BPB_start = $ BytesPerSec dw 200h ;512 bytes per sector SecPerCluster db 1 ;One sec per cluster ResSectors dw 1 ;Reserved sectors NumFATs db 1 ;Number of File Alloc tables RootDirEntries dw 8 ;Num of entries in root dir Sectors dw 8 ;Total number of sectors Media db 0F0h ;Media descriptor byte FATSectors dw 1 ;Number of sectors per FAT SecPerTrack dw 8 ;Num sectors per track Heads dw 1 ;Num of heads HiddenSectors dd 0 ;Num hidden sectors HugeSectors dd 0 ;Num of sec if > 32 Meg DriveNumber db 0 ;Used by DOS Reserved1 db 0 ;Used by DOS BootSignature db 29h ;IDs boot sector format VolumeID dd 12345678h ;Volume ID number VolumeLabel db "REDD " ;ASCII volume label FileSysType db "FAT12 " ;FAT system used boot_sector_end = $ ; ;Data needed for the driver ; req_header_ptr dd 0 ;Ptr to request header bpb_array dw offset BPB_start ;Array of BPB pointers keyname db "KEYBOARDIN " ;Name of keyboard file volume_name db "REDD ",0 ;ASCIIZ string of vol name cr_flag db 1 ;Append CR to video LFs even sys_year db 0 ;Time needed to set sys_month db 0 ; the time and date for sys_day db 0 ; screen file. sys_hours db 0 sys_minutes db 0 sys_seconds db 0 timer_low dw 0 ;Timer ticks since last timer_high dw 0 ; GetSysTime call. scrtick_low dw 0 ;Tick count at last screen scrtick_high dw 0 ; write. int08_active dw -1 ;Interrupt 8 active flag int08h dd -1 ;Old Timer Interrupt int10h dd -1 ;Old Video Interrupt ScreenHead dd -1 ;Head of screen buffer queue ScreenTop dw -1 ;Top of screen buffer ScreenBot dw -1 ;End of screen buffer ScreenTxtSec dw 2 ;Screen file num of sectors fileopen_count dw 0 ;Number of opened files root_update db 0 ;Indicates change in Root dir paste_flag db 0 pastedata_ptr dw 0 pastedata_end dw 0 fpclust_size dw 0 pastecluster dw 0 pastedirent_ptr dw 0 FATPtr dw 0 ;Ptr to FAT table FATSize dw 0 ;Sectors * 1.5 RootSize dw 0 ;Root entries * 32 DataPtr dw ? ;Ptr to data sector start jmptable dw offset init ;0 Initialize driver dw offset media_check ;1 Block device media check dw offset build_bpb ;2 Build BIOS parameter blk dw offset not_implimented ;3 I/O control read dw offset read ;4 Read dw offset not_implimented ;5 Non-destructive read dw offset not_implimented ;6 Get input status dw offset not_implimented ;7 Flush input dw offset write ;8 Write dw offset write ;9 Write with verify dw offset not_implimented ;A Get output status dw offset not_implimented ;B Output flush dw offset not_implimented ;C I/O control write dw offset open_device ;D Open device dw offset close_device ;E Close device dw offset removable_media ;F Removable media check dw offset not_implimented ;10 Output until busy dw offset not_implimented ;11 Reserved dw offset not_implimented ;12 Reserved dw offset not_implimented ;13 Generic I/O control dw offset not_implimented ;14 Reserved dw offset not_implimented ;15 Reserved dw offset not_implimented ;16 Reserved dw offset not_implimented ;17 Get logic drive mapping dw offset not_implimented ;18 Set logic drive mapping dw offset not_implimented ;19 I/O control query jmptable_end = $ max_cmd equ (offset jmptable_end - offset jmptable) shr 1 ;==================================================================== ;STRATEGY - Handles strategy calls from DOS by copying the request ; header pointer into an internal buffer. ;==================================================================== strategy proc far assume cs:code,ds:nothing,es:nothing mov word ptr cs:[req_header_ptr],bx mov word ptr cs:[req_header_ptr+2],es ret strategy endp ;==================================================================== ;INTERRUPT - Handles interrupt calls from DOS by implimenting the ; device driver functions ;==================================================================== interrupt proc far assume cs:code,ds:nothing,es:nothing push ax push bx push cx push dx push di push si push bp push ds push es pushf cld ;All string operations UP mov di,cs mov ds,di assume ds:code les di,req_header_ptr ;Get ptr to request header xor bx,bx mov bl,es:[di.Function] ;Get requested function cmp bl,max_cmd mov ax,8003h ;Load error status ja interrupt_exit nop shl bx,1 call [bx+jmptable] ;Call proper routine push ax cmp cs:root_update,0 je interrupt_1 call check_root interrupt_1: pop ax les di,req_header_ptr ;Get ptr to request header or ax,0100h ;Set done bit interrupt_exit: mov es:[di.Status],ax ;Save status in drvr header popf pop es pop ds pop bp pop si pop di pop dx pop cx pop bx pop ax ret interrupt endp ;-------------------------------------------------------------------- ;MEDIA CHECK - Media check function allows DOS to determine if the ; disk type in the drive has changed. ;Entry: ES:DI - Point to request header structure ;-------------------------------------------------------------------- media_check proc near assume cs:code,ds:code,es:nothing mov es:[di.mrReturn],0 ;Media may have been changed mov word ptr es:[di.rrVolumeID],offset volume_name mov word ptr es:[di.rrVolumeID+2],cs not_implimented: xor ax,ax ;Clear return code ret media_check endp ;-------------------------------------------------------------------- ;BUILD BPB - Build BIOS Parameter Block. ;Entry: ES:DI - Point to request header structure ;-------------------------------------------------------------------- build_bpb proc near assume cs:code,ds:code,es:nothing mov word ptr es:[di.bbrBPBAddress],offset BPB_start mov word ptr es:[di.bbrBPBAddress+2],cs xor ax,ax ret build_bpb endp ;-------------------------------------------------------------------- ;READ - Reads sectors from the block device ;Entry: ES:DI - Point to request header structure ;-------------------------------------------------------------------- read proc near assume cs:code,ds:code,es:nothing mov bx,es:[di.rrStartSec] mov cx,es:[di.rrBytesSec] push cx push di push es les di,es:[di.rrBuffer] nop read_1: call read_sector ;'Read' a sector inc bx ;Inc starting sector loop read_1 ;Read again if not done pop es ;Set output fields and term pop di pop cx mov es:[di.rrBytesSec],cx mov word ptr es:[di.rrVolumeID],offset volume_name mov word ptr es:[di.rrVolumeID+2],cs xor ax,ax ret read endp ;-------------------------------------------------------------------- ;WRITE - Writes sectors from the block device ;Entry: ES:DI - Point to request header structure ;-------------------------------------------------------------------- write proc near assume cs:code,ds:code,es:nothing mov bx,es:[di.rrStartSec] mov cx,es:[di.rrBytesSec] push cx push si push ds lds si,es:[di.rrBuffer] nop write_1: call write_sector ;'Write' a sector inc bx ;Inc starting sector loop write_1 ;Read again if not done pop ds pop si pop cx mov es:[di.rrBytesSec],cx mov word ptr es:[di.rrVolumeID],offset volume_name mov word ptr es:[di.rrVolumeID+2],cs xor ax,ax ret write endp ;-------------------------------------------------------------------- ;OPEN DEVICE - Indicates that a file has been opened on the drive ;Entry: ES:DI - Point to request header structure ;-------------------------------------------------------------------- open_device proc near assume cs:code,ds:code,es:nothing inc cs:fileopen_count xor ax,ax ret open_device endp ;-------------------------------------------------------------------- ;CLOSE DEVICE - Indicates that a file has been closed on the drive ;Entry: ES:DI - Point to request header structure ;-------------------------------------------------------------------- close_device proc near assume cs:code,ds:code,es:nothing dec cs:fileopen_count xor ax,ax ret close_device endp ;-------------------------------------------------------------------- ;REMOVABLE MEDIA - Informs DOS whether the drive is removable ;Entry: ES:DI - Point to request header structure ;-------------------------------------------------------------------- removable_media proc near assume cs:code,ds:code,es:nothing xor ax,ax ;Bit 9 = 0 - drive removable ret removable_media endp ;-------------------------------------------------------------------- ;READ SECTOR - Simulates a read of a mythical disk sector ;Entry: BX - Starting sector ; ES:DI - Ptr to data buffer to read data ;Exit: ES:DI - Points to byte beyond last data read out to DOS ;-------------------------------------------------------------------- read_sector proc near assume cs:code,ds:code,es:nothing push bx push cx cmp bx,1 ;Check what sector to read jb read_boot je read_FAT sub bx,3 jb read_root cmp bx,ScreenTxtSec ;See if reading SCREEN.TXT jb read_screen call getdata_ptr ;Compute buff for sector mov si,bx mov cx,BytesPerSec jmp short read_sector_1 read_screen: mov dx,BytesPerSec xchg bx,dx mov si,word ptr ScreenHead ;Read this sector as a mov ax,bx ; rotating buffer. The mul dx ; ScreenHead ptr points add si,ax ; to the start of the mov cx,ScreenBot ;See if starting past end cmp si,cx ; of buffer. jb read_screen_0 sub si,cx ;Yes, wrap ptr to buff start add si,ScreenTop read_screen_0: sub cx,si ;Compute len till end of buff sub bx,cx ;Sub read len from total jae read_screen_1 ;If read len more than total, mov cx,BytesPerSec ; change read len to total xor bx,bx ;Clear total. read_screen_1: rep movsb mov si,ScreenTop mov cx,bx jcxz read_sector_exit rep movsb jmp short read_sector_exit read_boot: mov si,offset boot_sector mov cx,offset boot_sector_end - offset boot_sector jmp short read_sector_1 read_FAT: mov si,FATPtr mov cx,FATSize jmp short read_sector_1 read_root: mov si,offset root_dir call set_time ;Set time for screen file mov cx,RootSize read_sector_1: mov dx,BytesPerSec ;Copy data sub dx,cx ;See how much is left for rep movsb ; a complete sector xor al,al mov cx,dx ;Fill in remainder of jcxz read_sector_exit ; sector with zeros. rep stosb read_sector_exit: pop cx pop bx ret read_sector endp ;-------------------------------------------------------------------- ;WRITE SECTOR - Simulates a write of a mythical disk sector ;Entry: BX - Starting sector ; DS:SI - Ptr to data buffer ;Exit: DS:SI - Points to byte beyond last data read into drive ;-------------------------------------------------------------------- write_sector proc near assume cs:code,ds:nothing,es:nothing push bx push cx push di push es mov ax,cs mov es,ax assume es:code cmp bx,1 ;Check what sector to write jb write_boot je write_FAT sub bx,3 jb write_root call getdata_ptr ;Compute buff for sector mov di,bx mov cx,BytesPerSec jmp short write_sector_1 write_boot: mov di,offset boot_sector mov cx,offset boot_sector_end - offset boot_sector jmp short write_sector_1 write_FAT: mov di,cs:FATPtr mov cx,cs:FATSize jmp short write_sector_1 write_root: mov di,offset root_dir mov cx,cs:RootSize inc cs:root_update write_sector_1: rep movsb write_sector_exit: pop es pop di pop cx pop bx ret write_sector endp ;-------------------------------------------------------------------- ;GETDATA PTR - Returns the offet in RAM for a given data sector ;Entry: BX - Cluster - 2 ;Exit: BX - Ptr to data ;-------------------------------------------------------------------- getdata_ptr proc near assume cs:code,ds:nothing,es:nothing push ax push dx mov ax,bx ;Copy starting data sec mul cs:BytesPerSec ;Mul by size of data sec mov bx,ax ;Add starting offset of add bx,cs:DataPtr ; data buffer. pop dx pop ax ret getdata_ptr endp ;-------------------------------------------------------------------- ;CHECK ROOT - Checks changes in the root directory ;-------------------------------------------------------------------- check_root proc near assume cs:code,ds:nothing,es:nothing push ds push es mov ax,cs mov ds,ax mov es,ax assume cs:code,ds:code,es:code mov root_update,0 ;Clear flag cmp paste_flag,0 ;Don't bother if we are jne check_root_exit ; already pasting. mov si,offset root_dir mov cx,RootDirEntries mov di,offset keyname check_root_1: push cx ;Scan through root looking push si ; for the name of the push di ; keyboard file. mov cx,11 repe cmpsb pop di pop si pop cx je check_root_2 add si,32 loop check_root_1 jmp short check_root_exit check_root_2: xor bx,bx or bx,[si+1ah] ;See if starting cluster set je check_root_exit mov cx,word ptr [si+1ch] ;Get file size or cx,cx je check_root_exit ;If 0, exit mov ax,cx xor dx,dx div BytesPerSec ;Compute number of sectors mov fpclust_size,dx ; and size of last sector. mov pastedirent_ptr,si mov pastecluster,bx call next_pasteclust ;Compute pointers to sector mov paste_flag,1 ;Allow paste check_root_exit: pop es pop ds ret check_root endp ;------------------------------------------------------------------------- ;DELETE FILE - Deletes a file from the driver disk ;Entry: SI - Pointer to directory entry for file ;------------------------------------------------------------------------- delete_file proc near assume cs:code,ds:code,es:nothing push cx xor ax,ax mov bx,[si+1ah] ;Get starting cluster delete_file_1: mov cx,bx call get_fat_entry xchg bx,cx call set_fat_entry ;Zero entry mov bx,cx cmp bx,0fffh ;See if last entry jne delete_file_1 mov byte ptr [si],0e5h ;Clear name pop cx ret delete_file endp ;------------------------------------------------------------------------- ; GET FAT ENTRY - Returns the contents of a 12 bit FAT entry ; Entry: BX - Entry into FAT table ; Exit: BX - Next entry ;------------------------------------------------------------------------- get_fat_entry proc near assume cs:code,ds:code,es:nothing push ax push di mov di,FATPtr add di,bx shr bx,1 ;12 bit FAT mov ax,ds:[bx+di] jnc get_fat_entry_2 shr ax,1 shr ax,1 shr ax,1 shr ax,1 get_fat_entry_2: and ah,0fh ;Clear top nibble get_fat_entry_3: mov bx,ax ;Copy entry data pop di pop ax ret get_fat_entry endp ;------------------------------------------------------------------------- ; SET FAT ENTRY - Writes a 12 bit FAT table entry ; Entry: BX - Pointer to fat table entry ; AX - Data to write to FAT table ;------------------------------------------------------------------------- set_fat_entry proc near assume cs:code,ds:code,es:nothing push ax push bx push di mov di,FATPtr add di,bx shr bx,1 ;12 bit FAT pushf add di,bx popf mov bx,ds:[di] ;Get data jc set_fat_1 ;Jump if odd and bx,0f000h ;Remove old data jmp short set_fat_2 set_fat_1: and bx,000fh ;Remove old data shl ax,1 shl ax,1 shl ax,1 shl ax,1 set_fat_2: or ax,bx mov ds:[di],ax ;Write data pop di pop bx pop ax ret set_fat_entry endp ;==================================================================== ;TIMER INT - Interrupt 8h timer hook. This routine keeps the time ; and, when necessary, pastes data into the keyboard buff ;==================================================================== timerint proc far assume cs:code,ds:nothing,es:nothing pushf add word ptr cs:timer_low,1 adc word ptr cs:timer_high,0 cmp cs:paste_flag,0 jne timerint_1 timerint_exit: popf jmp cs:[int08h] ;Jmp to old interrupt timerint_1: inc cs:int08_active jne timerint_exit2 push ax push ds mov ax,cs mov ds,ax assume ds:code timerint_2: call push_key jc timerint_exit1 cmp paste_flag,0 jne timerint_2 timerint_exit1: pop ds pop ax timerint_exit2: dec cs:int08_active jmp short timerint_exit timerint endp ;----------------------------------------------------------------------------- ; PUSH KEY Fills the keyboard buffer with data ; Exit: CF - Set if keyboard buffer full ; AX - modified ;----------------------------------------------------------------------------- push_key proc near assume ds:nothing,es:nothing push bx push di push si push es cld ;String moves UP mov ax,bios_data mov es,ax assume es:bios_data cli ;No interrupts mov di,es:[keybuff_tail] push di call inckeyptr cmp di,es:[keybuff_head] ;See if buffer full pop di stc je push_key_exit mov si,pastedata_ptr lodsb ;Get character to paste cmp si,pastedata_end jb push_key_3 push ax mov bx,pastecluster ;See if cluster is the last call get_fat_entry cmp bx,0fffh je push_key_1 mov pastecluster,bx call next_pasteclust ;Compute ptrs for next sector jmp short push_key_2 push_key_1: mov paste_flag,0 ;Disable paste mov si,pastedirent_ptr ;Delete paste file call delete_file push_key_2: pop ax push_key_3: mov pastedata_ptr,si or al,al ;Don't stuff null char je push_key_5 jns push_key_31 and ax,007fh ;Remove sign bit, clear AH xchg ah,al ;Place char in scan code jmp short push_key_4 push_key_31: cmp al,0ah ;Don't stuff line feeds je push_key_5 cmp al,1ah ;Don't stuff End Of File char je push_key_5 xor ah,ah ;Clear scan code cmp al,0dh ;If CR character, add proper jne push_key_4 ; scan code for Word Perfect mov ah,1ch push_key_4: mov es:[di],ax ;Don't use STOSW, ptr must call inckeyptr ; be updated by inckeyptr mov es:[keybuff_tail],di ;Save keybuff ptr push_key_5: clc push_key_exit: pop es pop si pop di pop bx ret push_key endp ;-------------------------------------------------------------------- ;NEXT PASTECLUST - Sets the paste variables for a sector ;Entry: BX - new sector ;-------------------------------------------------------------------- next_pasteclust proc near push dx push bx call get_fat_entry mov dx,BytesPerSec cmp bx,0fffh jne next_pc_1 mov dx,fpclust_size next_pc_1: pop bx sub bx,2 call getdata_ptr mov pastedata_ptr,bx add bx,dx mov pastedata_end,bx pop dx ret next_pasteclust endp ;----------------------------------------------------------------------------- ; INCKEYPTR Incriments the keyboard buffer pointer ; Entry: DI - Current Keyboard tail pointer ;----------------------------------------------------------------------------- inckeyptr proc near assume es:bios_data inc di ;Make room in buffer inc di cmp di,es:[keybuff_end] ;Get ptr to end of buffer jne inckeyptr_1 mov di,es:[keybuff_start] ;Get ptr to buffer offset inckeyptr_1: ret inckeyptr endp ;==================================================================== ;VID INT - Interrupt 10h video hook. This routine monitors and ; records any BIOS writes to the screen into the 'file' ; SCREEN.TXT. ;==================================================================== vidint proc far assume cs:code,ds:nothing,es:nothing cmp ah,9 jae vidint_1 vidint_exit: jmp cs:[int10h] ;Jmp to old interrupt vidint_1: push cx push di push es cmp ah,09h je vidint_wrtchr1 cmp ah,0ah je vidint_wrtchr1 cmp ah,0eh je vidint_wrtchr cmp ah,13h jne vidint_exit1 push ax push si push ds mov si,es mov ds,si mov si,bp ;Copy ptr to string les di,cs:ScreenHead ;Get ptr to buffer mov ah,al vidint_2: jcxz vidint_4 lodsb ;Read character call save_char ;Store character cmp ah,2 jb vidint_3 inc si ;Skip past attribute vidint_3: loop vidint_2 vidint_4: pop ds pop si pop ax jmp short vidint_5 vidint_wrtchr: mov cx,1 vidint_wrtchr1: les di,cs:ScreenHead ;Get ptr to buffer jcxz vidint_5 call save_char ;Save character loop vidint_wrtchr1 vidint_5: mov word ptr cs:ScreenHead,di pushf cli mov di,cs:timer_low ;Mark last time screen mov cx,cs:timer_high ; updated. mov cs:scrtick_low,di mov cs:scrtick_high,cx popf vidint_exit1: pop es pop di pop cx jmp vidint_exit vidint endp ;-------------------------------------------------------------------- ;SAVE CHAR - Saves a character into the SCREEN.TXT file ;-------------------------------------------------------------------- save_char proc near assume cs:code,ds:nothing,es:code cmp al,13 ;See if CR je save_char_2 cmp al,10 je save_char_3 save_char_0: stosb save_char_01: cmp di,cs:ScreenBot jae save_char_1 ret save_char_1: mov di,cs:ScreenTop ret save_char_2: mov cs:cr_flag,0 jmp short save_char_0 save_char_3: cmp cs:cr_flag,0 je save_char_0 stosb mov al,13 stosb mov al,10 jmp short save_char_01 ret save_char endp ;-------------------------------------------------------------------- ;INIT TIMER - Calls the BIOS to retrieve the system time ;-------------------------------------------------------------------- init_timer proc near assume cs:code,ds:code,es:nothing push bx mov ah,2 ;Get system time int 1ah mov al,ch call un_bcd mov sys_hours,al mov al,cl call un_bcd mov sys_minutes,al mov al,dh call un_bcd mov sys_seconds,al mov ah,4 ;Get system time int 1ah mov al,cl call un_bcd xor ah,ah cmp ch,19 ;See if next century je init_timer_1 add ax,100 init_timer_1: sub ax,80 ;Convert to relative date mov sys_year,al mov al,dh call un_bcd mov sys_month,al mov al,dl call un_bcd mov sys_day,al pushf cli mov timer_low,0 mov timer_high,0 popf pop bx ret init_timer endp ;-------------------------------------------------------------------- ;SET TIME - Sets the time of file in the directory ;Entry: SI - Pointer to the directory entry ;-------------------------------------------------------------------- set_time proc near assume cs:code,ds:code,es:nothing mov ax,scrtick_low mov dx,scrtick_high call compute_elapsed add al,sys_seconds cmp al,60 jb set_time_1 inc cl sub al,60 set_time_1: add cl,sys_minutes cmp cl,60 jb set_time_2 inc ch sub cl,60 set_time_2: add ch,sys_hours cmp ch,24 jb set_time_3 inc dh sub ch,24 set_time_3: shr al,1 ;Divide seconds by 2 and ax,1fh mov bh,cl ;Get minutes and bx,3f00h shr bx,1 shr bx,1 shr bx,1 or ax,bx mov bh,ch ;Get hours shl bx,1 shl bx,1 shl bx,1 and bx,0f800h or ax,bx mov [si+16h],ax ;Save time in dir entry mov al,sys_day mov cl,sys_month mov ch,sys_year or dh,dh je set_time_4 call inc_date ;Inc to next day set_time_4: and ax,3fh shl cl,1 shl cl,1 shl cl,1 shl cl,1 shl cx,1 or ax,cx mov [si+18h],ax ;Save date in dir entry ret set_time endp ;-------------------------------------------------------------------- ;COMPUTE ELAPSED - Computes the elapsed time from a 32 bit timer tick ; count. ;Entry: AX,DX - Timer tick count ;Exit: DH - Days ; CH - Hours ; CL - Minutes ; DL - Seconds ;-------------------------------------------------------------------- compute_elapsed proc near assume cs:code,ds:code,es:nothing push bx push di xor bx,bx mov ch,dl ;Save hours cmp dl,24 ;If longer than 24 hours, jb compute_1 ; compute days. push ax xor ax,ax xchg ax,dx mov di,24 div di mov bl,al ;Save days mov dx,ax mul di mov ch,al pop ax compute_1: xor dx,dx mov di,1092 ;Ticks per minute div di mov cl,al ;Save minutes xor ax,ax xchg ax,dx mov di,10 mul di mov di,182 div di mov dl,al mov di,ax mov dh,bl pop di pop bx ret compute_elapsed endp ;-------------------------------------------------------------------- ;INC DATE - Propigates a incrimented date though the month and year. ;Entry: AL - Day ; CL - Month ; CH - Years since 1980 ;-------------------------------------------------------------------- inc_date proc near inc al ;Incriment date push bx mov bx,1f1eh ;bh=31,bl=30 cmp cl,7 ;Up till Aug. odd numbered jbe inc_date_1 ; months have 31 days. xchg bl,bh ; After, even months have 31 inc_date_1: test cl,1 ;See if odd month je inc_date_2 ;No, branch xchg bl,bh inc_date_2: cmp cl,2 ;See if Feb jne inc_date_3 mov bl,28 test ch,3 ;Leap year if 4 year multiple jne inc_date_3 ; of 1980. Fails at 2100 mov bl,29 ; since 2100 not a leap year inc_date_3: cmp al,bl jbe inc_date_exit mov al,1 ;Set to 1st day of the month inc cl ;Inc month cmp cl,13 ;See if end of year jne inc_date_exit mov cl,1 ;Set to Jan. inc ch ;Inc year inc_date_exit: pop bx ret inc_date endp ;-------------------------------------------------------------------- ;UN BCD - Returns a binary number for one coded in BCD ;Entry: AL - BCD number ;Exit: AL - Binary number ;-------------------------------------------------------------------- un_bcd proc near assume cs:code,ds:nothing,es:nothing push bx mov bl,al shr al,1 shr al,1 shr al,1 shr al,1 mov ah,10 mul ah and bl,0fh add al,bl pop bx ret un_bcd endp ;-------------------------------------------------------------------- ;FINAL INSTALL - Initializes the data structures needed for the drive ;Entry: ES:DI - Point to request header structure ; DX - Size of data sectors ;-------------------------------------------------------------------- final_install proc near assume cs:code,ds:code,es:nothing mov di,cs mov es,di assume es:code mov di,offset root_dir + 64 mov cx,RootSize sub cx,64 xor ax,ax rep stosb mov di,FATPtr mov al,Media ;Initialize FAT stosb ;First FAT bytes contain mov ax,-1 ; media descriptor byte stosw ; followed by FF FF. mov cx,ScreenTxtSec mov bx,screen_start final_install_0: dec cx jcxz final_install_01 mov ax,bx inc ax call set_fat_entry mov bx,ax jmp short final_install_0 final_install_01: mov ax,-1 call set_fat_entry final_install_02: inc bx cmp bx,Sectors ja final_install_3 xor ax,ax call set_fat_entry jmp short final_install_02 final_install_3: mov di,DataPtr mov cx,dx ;Fill 1st data sector for mov al,' ' ; SCREEN.TXT file. Might rep stosb ; as well init the rest. mov ax,3510h ;Get video interrupt vector int 21h mov word ptr [int10h],bx mov word ptr [int10h+2],es mov ax,2510h ;Set to our handler mov dx,offset vidint int 21h mov ax,3508h ;Get timer interrupt vector int 21h mov word ptr [int08h],bx mov word ptr [int08h+2],es mov ax,2508h ;Set to our handler mov dx,offset timerint int 21h xor ax,ax ;Clear return code ret final_install endp even ;Keep things on even addrs ; ;Start root directory with entry for screen.txt ; root_dir db "SCREEN OUT" ;Name db 1 ;Attribute (Read only) db 10 dup (0) ;Reserved screen_time dw 0 ;Time of file screen_date dw 0 ;Date of file screen_start dw 2 ;Starting cluster screen_size dd 0 ;Size of file volumne_entry db "REDD " ;Name db 8 ;Attribute (Volume) db 10 dup (0) ;Reserved dw 0 ;Time of file dw 0 ;Date of file dw 0 ;Starting cluster dd 0 ;Size of file end_of_resident = $ ;-------------------------------------------------------------------- ;Non-resident data ;-------------------------------------------------------------------- initmsg db 13,10,"REDD installed as drive " initdrv db " :",13,10,10,'$' ;-------------------------------------------------------------------- ;INIT - Initializes the device driver ;Entry: ES:DI - Point to request header structure ;-------------------------------------------------------------------- init proc near assume cs:code,ds:code,es:nothing mov ah,9 ;Print copyright mov dx,offset program int 21h call init_timer ;Init driver clock mov bx,offset root_dir mov ax,32 ;Compute size of root dir mov dx,RootDirEntries mul dx mov RootSize,ax add bx,ax mov FATPtr,bx mov ax,Sectors mov dx,ax ;Mul sectors by 1.5 shr ax,1 adc ax,dx mov FATSize,ax add bx,ax mov DataPtr,bx mov word ptr ScreenHead,bx ;Init screen buffer ptrs to mov word ptr ScreenHead+2,cs ; 1st data sector. mov ScreenTop,bx mov ax,ScreenTxtSec mul BytesPerSec mov word ptr screen_size,ax add ax,bx mov ScreenBot,ax mov ax,Sectors ;Compute size of data mul BytesPerSec ; sectors. mov dx,ax ;Save data sector size add ax,bx les di,req_header_ptr ;Get ptr to request header mov cl,es:[di.irDriveNumber] ; the drive number being add cl,'A' ; used. mov initdrv,cl mov word ptr es:[di.irEndAddress],ax ;Set memory mov word ptr es:[di.irEndAddress+2],cs ; size mov word ptr es:[di.irParmAddress],offset BPB_array mov word ptr es:[di.irParmAddress+2],cs mov word ptr es:[di.irUnits],1 push dx mov ah,9 ;Print message indicating mov dx,offset initmsg ; disk letter. int 21h pop dx jmp final_install init endp code ends end