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Assembly Source File | 1984-09-03 | 10.6 KB | 315 lines

name dump page 55,132 title DUMP --- Display File Contents ;DUMP --- a utility to display the contents of a file in hex ;and ASCII format. Requires PC-DOS or MS-DOS 2.0. ;Used in the form: ;A>dump path\filename.ext [>device] ;(item in square brackets is optional) cr equ 0dh ;ASCII carriage return lf equ 0ah ;ASCII line feed blank equ 20h ;ASCII space code command equ 80h ;buffer for command tail blksize equ 128 ;size of input file records output_handle equ 1 ;handle of standard output de ;(can be redirected) error_handle equ 2 ;handle of standard error dev ;(not redirectable) cseg segment para public 'CODE' assume cs:cseg,ds:data,es:data,ss:stack dump proc far ;entry point from PC-DOS push ds ;save DS:0000 for final xor ax,ax ;return to PC-DOS push ax mov ax,data ;make our data segment mov es,ax ;addressable via ES register. mov ah,30h ;check version of PC-DOS. int 21h cmp al,2 jae dump1 ;proceed, DOS 2.0 or greater. mov dx,offset msg3 ;DOS 1.x --- print error mess mov ax,es ;we must use the old PC-DOS mov ds,ax ;string output function since mov ah,9 ;handles are not available in int 21h ;this version of PC-DOS. ret dump1: call get_filename ;get path and file spec.for ;input file from command line mov ax,es ;set DS = ES for remainder mov ds,ax ;of program. jnc dump2 ;jump,got acceptable name. mov dx,offset msg2 ;missing or illegal filespec. mov cx,msg2_length jmp dump9 ;print error message and exit dump2: call open_input ;now try to open input file jnc dump3 ;jump, opened input ok mov dx,offset msg1 ;open of input file failed. mov cx,msg1_length jmp dump9 ;print error msg and exit. dump3: call read_block ;initialize input file buffer jnc dump4 ;jump,got a block mov dx,offset msg4 ;empty file, print error mov cx,msg4_length jmp dump9 ;message and exit ;file successfully opened. dump4: ;now convert and display it! call get_char ;read 1 character from input. jc dump8 ;jump,end of file inc input_addr ;update relative file positio or bx,bx ;is this 1st char of block? jnz dump5 ;no call print_heading dump5: and bx,0fh ;is this first byte of 16? jnz dump6 ;no, jump push ax ;save the byte mov di,offset output ;convert relative file addr. mov ax,input_addr ;for output string call conv_word pop ax dump6: ;store ASCII version of chara ;if it is alphanumeric, mov di,offset outputb add di,bx ;calculate output string addr mov byte ptr[di],'.' ;if it is control character, cmp al,blank ;just print a dot. jb dump7 ;jump,not alphanumeric, cmp al,7eh ja dump7 ;jump not alphanumberic, mov [di],al ;store ASCII character. dump7: push bx ; save current offset mov di,offset outputa ; offset of hex area add di,bx ; + 3*bx is where next add di,bx ; pair of hex digits go add di,bx call conv_byte ;value => printable hex digits pop bx ;restore offset value cmp bx,0fh ;16 bytes converted? jne dump4 ; no go back and do another mov dx,offset output ; mov cx,output_length call write_std jmp dump4 dump8: call close_input ret dump9: call write_error ret dump endp get_filename proc near mov si,offset command mov di,offset input_name cld lodsb or al,al jz get_filename4 get_filename1: lodsb cmp al,cr je get_filename4 cmp al,blank jz get_filename1 get_filename2: stosb lodsb cmp al,cr je get_filename3 cmp al,blank jne get_filename2 get_filename3: clc ret get_filename4: stc ret get_filename endp open_input proc near mov dx,offset input_name ; ds:dx => addr filename mov al,0 mov ah,3dh ; open file function in DOS int 21h mov input_handle,ax ret open_input endp close_input proc near mov bx,input_handle mov ah,3eh ; DOS closefile function number int 21h ret close_input endp get_char proc near mov bx,input_ptr cmp bx,blksize ; is this the end of a block? jne get_char1 mov input_ptr,0 ; if eob then set pointer to 0 call read_block ; and get another block jnc get_char ret get_char1: mov al,[input_buffer+bx] inc input_ptr clc ; set carry 0 since not eof ret get_char endp read_block proc near mov bx,input_handle mov cx,blksize mov dx,offset input_buffer mov ah,3fh ; dos read disk function int 21h inc input_block mov input_ptr,0 or ax,ax ;ax contains # of bytes read jnz read_block1 ; if not eof ret (carry is 0) stc ; else set carry and ret read_block1: ret read_block endp write_std proc near mov bx,output_handle mov ah,40h ; write device function number int 21h ret write_std endp write_error proc near mov bx,error_handle mov ah,40h int 21h ret write_error endp print_heading proc near push ax push bx mov di,offset headinga mov ax,input_block call conv_word mov dx,offset heading mov cx,heading_length call write_std pop bx pop ax ret print_heading endp conv_word proc near push ax mov al,ah call conv_byte pop ax call conv_byte ret conv_word endp conv_byte proc near sub ah,ah ; zero ah reg mov cl,16 div cl call ascii stosb mov al,ah call ascii stosb ret conv_byte endp ascii proc near add al,'0' ; convert al to ascii char cmp al,'9' jle ascii2 add al,'a'-'9'-1 ; offset to a-f hex range ascii2: ret ascii endp cseg ends data segment para public'DATA' input_name db 64 dup(0) ; buffer for input filespec input_handle dw 0 ;token from DOS for input file input_ptr dw 0 ;pointer to input de-blocking buffer input_addr dw 0 ; relatve address in file input_block dw 0 ;current 128k block byte number output db 'nnnn',blank,blank outputa db 16 dup('00',blank) db blank outputb db '0123456789abcdef',cr,lf output_length equ $-output heading db cr,lf,'Record',blank headinga db 'nnnn',blank,blank,cr,lf db 7 dup(blank) db '0 1 2 3 4 5 6 7 ' db '8 9 A B C D E F',cr,lf heading_length equ $-heading input_buffer db blksize dup(?) msg1 db cr,lf db 'Cannot open file' msg1_length equ $-msg1 msg2 db cr,lf db 'Missing file name' msg2_length equ $-msg2 msg3 db cr,lf db 'Requires DOS 2.0 or greater' msg3_length equ $-msg3 msg4 db cr,lf db 'Empty file',cr,lf msg4_length equ $-msg4 data ends stack segment para stack'STACK' db 64 dup(?) stack ends end dump