Microsoft Programmer's Library 1.3

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/ Microsoft Programmer's Library 1.3 / Microsoft-Programers-Library-v1.3.iso / sampcode / advmsdos / chap08 / dump.asm next >

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Assembly Source File | 1988-10-01 | 11.0 KB | 437 lines

title DUMP --- display file contents page 55,132 ; ; DUMP --- Display contents of file in hex and ASCII ; ; Build: C>MASM DUMP; ; C>LINK DUMP; ; ; Usage: C>DUMP unit:\path\filename.exe [ >device ] ; ; Copyright 1988 Ray Duncan ; cr equ 0dh ; ASCII carriage return lf equ 0ah ; ASCII line feed tab equ 09h ; ASCII tab code blank equ 20h ; ASCII space code cmd equ 80h ; buffer for command tail blksize equ 16 ; input file record size stdin equ 0 ; standard input handle stdout equ 1 ; standard output handle stderr equ 2 ; standard error handle _TEXT segment word public 'CODE' assume cs:_TEXT,ds:_DATA,es:_DATA,ss:STACK dump proc far ; entry point from MS-DOS push ds ; save DS:0000 for final xor ax,ax ; return to MS-DOS, in case push ax ; Function 4CH can't be used. mov ax,_DATA ; make our data segment mov ds,ax ; addressable via DS register. ; check MS-DOS version mov ax,3000h ; Fxn 30H = get version int 21h ; transfer to MS-DOS cmp al,2 ; major version 2 or later? jae dump1 ; yes, proceed ; if MS-DOS 1.x, display ; error message and exit mov dx,offset msg3 ; DS:DX = message address mov ah,9 ; Fxn 9 = print string int 21h ; transfer to MS-DOS ret ; then exit the old way dump1: ; check if filename present mov bx,offset cmd ; ES:BX = command tail call argc ; count command arguments cmp ax,2 ; are there 2 arguments? je dump2 ; yes, proceed ; missing filename, display ; error message and exit mov dx,offset msg2 ; DS:DX = message address mov cx,msg2_len ; CX = message length jmp dump9 ; go display it dump2: ; get address of filename mov ax,1 ; AX = argument number ; ES:BX still = command tail call argv ; returns ES:BX = address, ; and AX = length mov di,offset fname ; copy filename to buffer mov cx,ax ; CX = length dump3: mov al,es:[bx] ; copy one byte mov [di],al inc bx ; bump string pointers inc di loop dump3 ; loop until string done mov byte ptr [di],0 ; add terminal null byte mov ax,ds ; make our data segment mov es,ax ; addressable by ES too ; now open the file mov ax,3d00h ; Fxn 3DH = open file ; mode 0 = read only mov dx,offset fname ; DS:DX = filename int 21h ; transfer to MS-DOS jnc dump4 ; jump, open successful ; open failed, display ; error message and exit mov dx,offset msg1 ; DS:DX = message address mov cx,msg1_len ; CX = message length jmp dump9 ; go display it dump4: mov fhandle,ax ; save file handle dump5: ; read block of file data mov bx,fhandle ; BX = file handle mov cx,blksize ; CX = record length mov dx,offset fbuff ; DS:DX = buffer mov ah,3fh ; Fxn 3FH = read int 21h ; transfer to MS-DOS mov flen,ax ; save actual length cmp ax,0 ; end of file reached? jne dump6 ; no, proceed cmp word ptr fptr,0 ; was this the first read? jne dump8 ; no, exit normally ; display empty file ; message and exit mov dx,offset msg4 ; DS:DX = message address mov cx,msg4_len ; CX = length jmp dump9 ; go display it dump6: ; display heading at ; each 128 byte boundary test fptr,07fh ; time for a heading? jnz dump7 ; no, proceed ; display a heading mov dx,offset hdg ; DS:DX = heading address mov cx,hdg_len ; CX = heading length mov bx,stdout ; BX = standard output mov ah,40h ; Fxn 40H = write int 21h ; transfer to MS-DOS dump7: call conv ; convert binary record ; to formatted ASCII ; display formatted output mov dx,offset fout ; DX:DX = output address mov cx,fout_len ; CX = output length mov bx,stdout ; BX = standard output mov ah,40h ; Fxn 40H = write int 21h ; transfer to MS-DOS jmp dump5 ; go get another record dump8: ; close input file mov bx,fhandle ; BX = file handle mov ah,3eh ; Fxn 3EH = close int 21h ; transfer to MS-DOS mov ax,4c00h ; Fxn 4CH = terminate, ; return code = 0 int 21h ; transfer to MS-DOS dump9: ; display message on ; standard error device ; DS:DX = message address ; CX = message length mov bx,stderr ; standard error handle mov ah,40h ; Fxn 40H = write int 21h ; transfer to MS-DOS mov ax,4c01h ; Fxn 4CH = terminate, ; return code = 1 int 21h ; transfer to MS-DOS dump endp conv proc near ; convert block of data ; from input file mov di,offset fout ; clear output format mov cx,fout_len-2 ; area to blanks mov al,blank rep stosb mov di,offset fout ; convert file offset mov ax,fptr ; to ASCII for output call w2a mov bx,0 ; init. buffer pointer conv1: mov al,[fbuff+bx] ; fetch byte from buffer mov di,offset foutb ; point to output area ; format ASCII part... ; store '.' as default mov byte ptr [di+bx],'.' cmp al,blank ; in range 20H - 7EH? jb conv2 ; jump, not alphanumeric. cmp al,7eh ; in range 20H - 7EH? ja conv2 ; jump, not alphanumeric. mov [di+bx],al ; store ASCII character. conv2: ; format hex part... mov di,offset fouta ; point to output area add di,bx ; base addr + (offset*3) add di,bx add di,bx call b2a ; convert byte to hex inc bx ; advance through record cmp bx,flen ; entire record converted? jne conv1 ; no, get another byte ; update file pointer add word ptr fptr,blksize ret conv endp w2a proc near ; convert word to hex ASCII ; call with AX = value ; DI = addr for string ; returns AX, DI, CX destroyed push ax ; save copy of value mov al,ah call b2a ; convert upper byte pop ax ; get back copy call b2a ; convert lower byte ret w2a endp b2a proc near ; convert byte to hex ASCII ; call with AL=binary value ; DI=addr for string ; returns AX, DI, CX modified sub ah,ah ; clear upper byte mov cl,16 div cl ; divide byte by 16 call ascii ; quotient becomes the first stosb ; ASCII character mov al,ah call ascii ; remainder becomes the stosb ; second ASCII character ret b2a endp ascii proc near ; convert value 0-0FH in AL ; into "hex ASCII" character add al,'0' ; offset to range 0-9 cmp al,'9' ; is it > 9? jle ascii2 ; no, jump add al,'A'-'9'-1 ; offset to range A-F, ascii2: ret ; return AL = ASCII char. ascii endp argc proc near ; count command line arguments ; call with ES:BX = command line ; returns AX = argument count push bx ; save original BX and CX push cx ; for later mov ax,1 ; force count >= 1 argc1: mov cx,-1 ; set flag = outside argument argc2: inc bx ; point to next character cmp byte ptr es:[bx],cr je argc3 ; exit if carriage return cmp byte ptr es:[bx],blank je argc1 ; outside argument if ASCII blank cmp byte ptr es:[bx],tab je argc1 ; outside argument if ASCII tab ; otherwise not blank or tab, jcxz argc2 ; jump if already inside argument inc ax ; else found argument, count it not cx ; set flag = inside argument jmp argc2 ; and look at next character argc3: pop cx ; restore original BX and CX pop bx ret ; return AX = argument count argc endp argv proc near ; get address & length of ; command line argument ; call with ES:BX = command line ; AX = argument no. ; returns ES:BX = address ; AX = length push cx ; save original CX and DI push di or ax,ax ; is it argument 0? jz argv8 ; yes, jump to get program name xor ah,ah ; initialize argument counter argv1: mov cx,-1 ; set flag = outside argument argv2: inc bx ; point to next character cmp byte ptr es:[bx],cr je argv7 ; exit if carriage return cmp byte ptr es:[bx],blank je argv1 ; outside argument if ASCII blank cmp byte ptr es:[bx],tab je argv1 ; outside argument if ASCII tab ; if not blank or tab... jcxz argv2 ; jump if already inside argument inc ah ; else count arguments found cmp ah,al ; is this the one we're looking for? je argv4 ; yes, go find its length not cx ; no, set flag = inside argument jmp argv2 ; and look at next character argv4: ; found desired argument, now ; determine its length... mov ax,bx ; save param. starting address argv5: inc bx ; point to next character cmp byte ptr es:[bx],cr je argv6 ; found end if carriage return cmp byte ptr es:[bx],blank je argv6 ; found end if ASCII blank cmp byte ptr es:[bx],tab jne argv5 ; found end if ASCII tab argv6: xchg bx,ax ; set ES:BX = argument address sub ax,bx ; and AX = argument length jmp argvx ; return to caller argv7: xor ax,ax ; set AX = 0, argument not found jmp argvx ; return to caller argv8: ; special handling for argv=0 mov ax,3000h ; check if DOS 3.0 or later int 21h ; (force AL=0 in case DOS 1) cmp al,3 jb argv7 ; DOS 1 or 2, return null param. mov es,es:[2ch] ; get environment segment from PSP xor di,di ; find the program name by xor al,al ; first skipping over all the mov cx,-1 ; environment variables... cld argv9: repne scasb ; scan for double null (can't use scasb ; (SCASW since might be odd addr.) jne argv9 ; loop if it was a single null add di,2 ; skip count word in environment mov bx,di ; save program name address mov cx,-1 ; now find its length... repne scasb ; scan for another null byte not cx ; convert CX to length dec cx mov ax,cx ; return length in AX argvx: ; common exit point pop di ; restore original CX and DI pop cx ret ; return to caller argv endp _TEXT ends _DATA segment word public 'DATA' fname db 64 dup (0) ; buffer for input filespec fhandle dw 0 ; token from PCDOS for input file. flen dw 0 ; actual length read fptr dw 0 ; relative address in file fbuff db blksize dup (?) ; data from input file fout db 'nnnn' ; formatted output area db blank,blank fouta db 16 dup ('nn',blank) db blank foutb db 16 dup (blank),cr,lf fout_len equ $-fout hdg db cr,lf ; heading for each 128 bytes db 7 dup (blank) ; of formatted output db '0 1 2 3 4 5 6 7 ' db '8 9 A B C D E F',cr,lf hdg_len equ $-hdg msg1 db cr,lf db 'dump: file not found' db cr,lf msg1_len equ $-msg1 msg2 db cr,lf db 'dump: missing file name' db cr,lf msg2_len equ $-msg2 msg3 db cr,lf db 'dump: wrong MS-DOS version' db cr,lf,'$' msg4 db cr,lf db 'dump: empty file' db cr,lf msg4_len equ $-msg4 _DATA ends STACK segment para stack 'STACK' db 64 dup (?) STACK ends end dump