Reverse Code Engineering RCE CD +sandman 2000/ReverseCodeEngineeringRceCdsandman2000.iso/RCE/Library/Manuels & Misc/Assembly/AOA.ZIP/CH15/FCMP.ASM

Assembly Source File | 1996-03-25 | 4.1 KB | 221 lines

; FCMP.ASM-    A file comparison program that demonstrates the use
;        of the 80x86 string instructions.

        .xlist
        include     stdlib.a
        includelib    stdlib.lib
        .list

dseg        segment    para public 'data'

Name1        dword    ?        ;Ptr to filename #1
Name2        dword    ?        ;Ptr to filename #2
Handle1        word    ?        ;File handle for file #1
Handle2        word    ?        ;File handle for file #2
LineCnt        word    0        ;# of lines in the file.

Buffer1        db    256 dup (0)    ;Block of data from file 1
Buffer2        db    256 dup (0)    ;Block of data from file 2

dseg        ends

wp        equ    <word ptr>


cseg        segment    para public 'code'
        assume    cs:cseg, ds:dseg


; Error- Prints a DOS error message depending upon the error type.

Error        proc    near
        cmp    ax, 2
        jne    NotFNF
        print
        db    "File not found",0
        jmp    ErrorDone

NotFNF:        cmp    ax, 4
        jne    NotTMF
        print
        db    "Too many open files",0
        jmp    ErrorDone

NotTMF:        cmp    ax, 5
        jne    NotAD
        print
        db    "Access denied",0
        jmp    ErrorDone

NotAD:        cmp    ax, 12
        jne    NotIA
        print
        db    "Invalid access",0
        jmp    ErrorDone

NotIA:
ErrorDone:    putcr
        ret
Error        endp




; Okay, here's the main program.  It opens two files, compares them, and
; complains if they're different.

Main        proc
        mov    ax, seg dseg        ;Set up the segment registers
        mov    ds, ax
        mov    es, ax

        meminit

; File comparison routine.  First, open the two source files.

        argc
        cmp    cx, 2        ;Do we have two filenames?
        je    GotTwoNames
        print
        db    "Usage: fcmp file1 file2",cr,lf,0
        jmp    Quit

GotTwoNames:    mov    ax, 1        ;Get first file name
        argv
        mov    wp Name1, di
        mov    wp Name1+2, es

; Open the files by calling DOS.

        mov    ax, 3d00h    ;Open for reading
        lds    dx, Name1
        int    21h
        jnc    GoodOpen1
        printf
        db    "Error opening %^s:",0
        dd    Name1
        call    Error
        jmp    Quit

GoodOpen1:    mov    dx, dseg
        mov    ds, dx
        mov    Handle1, ax

        mov    ax, 2        ;Get second file name
        argv
        mov    wp Name2, di
        mov    wp Name2+2, es

        mov    ax, 3d00h    ;Open for reading
        lds    dx, Name2
        int    21h
        jnc    GoodOpen2
        printf
        db    "Error opening %^s:",0
        dd    Name2
        call    Error
        jmp    Quit

GoodOpen2:    mov    dx, dseg
        mov    ds, dx
        mov    Handle2, ax

; Read the data from the files using blocked I/O
; and compare it.

        mov    LineCnt, 1
CmpLoop:    mov    bx, Handle1    ;Read 256 bytes from
        mov    cx, 256        ; the first file into
        lea    dx, Buffer1    ; Buffer1.
        mov    ah, 3fh
        int    21h
        jc    FileError
        cmp    ax, 256        ;Leave if at EOF.
        jne    EndOfFile

        mov    bx, Handle2    ;Read 256 bytes from
        mov    cx, 256        ; the second file into
        lea    dx, Buffer2    ; Buffer2
        mov    ah, 3fh
        int    21h
        jc    FileError
        cmp    ax, 256        ;If we didn't read 256 bytes,
        jne    BadLen        ; the files are different.

; Okay, we've just read 256 bytes from each file, compare the buffers
; to see if the data is the same in both files.

        mov    ax, dseg
        mov    ds, ax
        mov    es, ax
        mov    cx, 256
        lea    di, Buffer1
        lea    si, Buffer2
        cld
    repe    cmpsb
        jne    BadCmp
        jmp    CmpLoop


FileError:    print
        db    "Error reading files: ",0
        call    Error
        jmp    Quit


BadLen:        print
        db    "File lengths were different",cr,lf,0

BadCmp:        print
        db      7,"Files were not equal",cr,lf,0

        mov    ax, 4c01h        ;Exit with error.
        int    21h


; If we reach the end of the first file, compare any remaining bytes
; in that first file against the remaining bytes in the second file.

EndOfFile:    push    ax            ;Save final length.
        mov    bx, Handle2
        mov    cx, 256
        lea    dx, Buffer2
        mov    ah, 3fh
        int    21h
        jc    BadCmp

        pop    bx            ;Retrieve file1's length.
        cmp    ax, bx            ;See if file2 matches it.
        jne    BadLen

        mov    cx, ax            ;Compare the remaining
        mov    ax, dseg        ; bytes down here.
        mov    ds, ax
        mov    es, ax
        lea    di, Buffer2
        lea    si, Buffer1
    repe    cmpsb
        jne    BadCmp

Quit:        mov    ax, 4c00h        ;Set Exit code to okay.
        int    21h
Main        endp

cseg            ends



; Allocate a reasonable amount of space for the stack (2k).

sseg        segment    para stack 'stack'
stk        db    256 dup ("stack   ")
sseg        ends


; zzzzzzseg must be the last segment that gets loaded into memory!

zzzzzzseg    segment    para public 'zzzzzz'
LastBytes    db    16 dup (?)
zzzzzzseg    ends
        end    Main