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Assembly Source File | 1984-04-25 | 13.8 KB | 343 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 2.0 or MS-DOS 2.0. ; Used in the form: ; A>dump path\filename.ext [ >device ] ; (item in square brackets is optional) ; version 1.0 March 25, 1984 ; Copyright (c) 1984 by Ray Duncan ; May be freely reproduced for non-commercial use. 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 device ;(can be redirected) error_handle equ 2 ;handle of standard error device ;(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 message; 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 tail. 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 position 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 character, ;if it is alphanumeric, mov di,offset outputb add di,bx ;calculate output string address 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 alphanumeric. mov [di],al ;store ASCII character. dump7: ;now convert binary byte ;to hex ASCII equivalent. push bx ;save offset 0-15 of this byte. ;calc. its position in ;output string. mov di,offset outputa add di,bx ;base addr + (offset*3) add di,bx add di,bx call conv_byte ;convert data byte to hex pop bx ;restore byte offset cmp bx,0fh ;16 bytes converted yet? jne dump4 ;no,get another byte mov dx,offset output mov cx,output_length call write_std ;yes, print the line jmp dump4 ;get next char. from input file. dump8: ;end of file detected, call close_input ;close input file. ret ;now return to PC-DOS. dump9: ;come here to print message ;on standard error device, call write_error ;and return control to PC-DOS ret dump endp get_filename proc near ;process name of input file ;return Carry = 0 if successful ;return Carry = 1 if no filename ;DS:SI <- addr command line mov si,offset command ;ES:DI <- addr filespec buffer mov di,offset input_name cld lodsb ;any command line present? or al,al ;return error status if not. jz get_filename4 get_filename1: ;scan over leading blanks lodsb ;to file name. cmp al,cr ;if we hit carriage return... je get_filename4 ;jump, name is missing cmp al,20h ;is this a blank? jz get_filename1 ;if so keep scanning. get_filename2: ;found first char of name, stosb ;move last char. to output ;file name buffer. lodsb ;check next character, found cmp al,cr ;carriage return yet? je get_filename3 ;yes,exit with success code. cmp al,20h ;is this a blank? jne get_filename2 ;if not keep moving chars. get_filename3: ;exit with carry =0 clc ;for success flag ret get_filename4: ;exit with carry =1 stc ;for error flag ret get_filename endp open_input proc near ;open input file ;DS:DX=addr filename mov dx,offset input_name mov al,0 ;AL=0 for read only mov ah,3dh ;function 3dh=open int 21h ;handle returned in AX, mov input_handle,ax ;save it for later. ret ;CY is set if error open_input endp close_input proc near ;close input file mov bx,input_handle ;BX=handle mov ah,3eh int 21h ret close_input endp get_char proc near ;get one character from input buffer ;return AL = char, BX = buffer offset ;return CY flag = 1 if end of file mov bx,input_ptr ;is pointer at end of buffer? cmp bx,blksize jne get_char1 ;no,jump ;yes, buffer is exhausted, mov input_ptr,0 call read_block ;new block must be read from disk. jnc get_char ;got block, start routine over. ret ;end of file detected ;so return CY flag = True. get_char1: ;get data byte into AL, mov al,[input_buffer+bx] inc input_ptr ;bump input buffer pointer. clc ;return CY flag =0 since ret ;not end of file. get_char endp read_block proc near ;read block of data from input file. ;return CY flag = 0 if read ok. ; CY flag = 1 if end of file. mov bx,input_handle ;request read from PC-DOS. mov cx,blksize mov dx,offset input_buffer mov ah,3fh int 21h ;initialize pointers inc input_block mov input_ptr,0 or ax,ax ;was anything read in? (the OR ; incidentally turns off the CY flag) jnz read_block1 ;yes,jump stc ;no,end of file so return CY=True read_block1: ret read_block endp write_std proc near ;write string to standard output. ;call DX = addr of output string ; CX = length of string mov bx,output_handle;BX=handle for standard list device. mov ah,40h ;function 40h=write to device. int 21h ;request service from DOS. ret write_std endp write_error proc near ;write string to standard error device. ;call DX = addr of output string ; CX = length of string mov bx,error_handle ;BX=handle for standard error device. mov ah,40h ;function 40h=write to device. int 21h ;request service from DOS. ret write_error endp print_heading proc near ;print record number and heading push ax ;for a block of data push bx ;first save registers mov di,offset headinga mov ax,input_block call conv_word ;convert record number to ASCII mov dx,offset heading mov cx,heading_length call write_std ;now print heading pop bx ;restore registers pop ax ret ;and exit print_heading endp conv_word proc near ;convert 16-bit binary word ; to hex ASCII ;call with AX=binary value ; DI=addr to store string ;returns AX, DI, CX destroyed push ax mov al,ah call conv_byte ;convert upper byte pop ax call conv_byte ;convert lower byte ret conv_word endp conv_byte proc near ;convert binary byte to hex ASCII ;call with AL=binary value ; DI=addr to store string ;returns AX, DI, CX modified sub ah,ah ;clear upper byte mov cl,16 div cl ;divide binary data by 16 call ascii ;the quotient becomes the first stosb ;ASCII character mov al,ah call ascii ;the remainder becomes the stosb ;second ASCII character ret conv_byte endp ascii proc near ;convert bottom 4 bits in AL add al,'0' ;into the hex ASCII character cmp al,'9' jle ascii2 ;jump if in range 0-9, add al,'A'-'9'-1 ;offset it to range A-F, ascii2: ret ;return ASCII char. in AL. 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 PCDOS for input file. input_ptr dw 0 ;pointer to input deblocking buffer input_addr dw -1 ;relative address in file input_block dw 0 ;current 128 byte block 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 (?) ;deblocking buffer for input file msg1 db cr,lf db 'Cannot find input file.' db cr,lf msg1_length equ $-msg1 msg2 db cr,lf db 'Missing file name.' db cr,lf msg2_length equ $-msg2 msg3 db cr,lf db 'Requires PC-DOS version 2 or greater.' db cr,lf,'$' msg4 db cr,lf,'Empty file.',cr,lf msg4_length equ $-msg4 data ends stack segment para stack 'STACK' db 64 dup (?) stack ends end dump Press ENTER to continue: