String processing routines

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FoXx

Joined: 25 Feb 2025
Posts: 24

FoXx 15 Dec 2025, 13:15

In the early 2000s, I developed several string processing routines. They've stood the test of time. I'd like to share that code.

Code:

continue        equ @r
skip            equ @f

;------------------------------------------------
;       * * *  String To DWORD  * * *
;------------------------------------------------
proc StrToInt

;       mov ESI, lpBuffer

        xor EDX, EDX
        or  ESI, ESI
        jz  skip

                mov ECX, EDX
                mov EBX, EDX
                mov  BL, 10
.scan:
                lodsb
                cmp AL, '0'
                jb  skip

                cmp AL, '9' 
                ja  skip

                        sub AL, '0'
                        mov CL, AL

                        mov EAX, EDX
                        mul EBX 
                        add EAX, ECX
                        mov EDX, EAX
        
                jmp .scan
@@:
        mov EAX, EDX    ;       return Value
        ret
endp

;------------------------------------------------
;       * * *  INT To String  * * *
;------------------------------------------------
proc IntToStr

;       mov EDI, lpBuffer
;       mov ECX, Value

        xor EBX, EBX
        mov  BL, 10
        mov EAX, ECX

        @@:
                inc EDI
                xor EDX, EDX
                div EBX

                or EAX, EAX
                jnz continue

        mov ESI, EDI
        mov EAX, ECX

        @@:
                dec EDI
                xor EDX, EDX
                div EBX

                add DL, '0'
                mov [EDI], DL

                or EAX, EAX
                jnz continue

        mov EDI, ESI    ;       set the end position
        ret
endp

;------------------------------------------------
;       * * *  HEX To String  * * *
;------------------------------------------------
sHexScaleChar   DB '0123456789ABCDEF'   ;        it's in the data section

proc HexToStr

;   mov EDI, lpBuffer
;   mov EDX, Value

        mov ESI, sHexScaleChar
        xor ECX, ECX
        mov EBX, ECX
        mov  CL, 8

        @@:
                rol EDX, 4
                mov BL,  DL
                and BL,  01111b         ;       get 4 bits

                mov AL, [ESI+EBX]
                stosb

                loop continue
        ret
endp

Last edited by FoXx on 15 Dec 2025, 14:20; edited 2 times in total

15 Dec 2025, 13:15

AsmGuru62

Joined: 28 Jan 2004
Posts: 1749
Location: Toronto, Canada

AsmGuru62 15 Dec 2025, 13:51

Very nice looking code!
Especially, I like how you use blank lines.
I do that too.

15 Dec 2025, 13:51

FoXx

Joined: 25 Feb 2025
Posts: 24

FoXx 15 Dec 2025, 14:06

AsmGuru62 wrote:

Very nice looking code!
Especially, I like how you use blank lines.
I do that too.

Thank you

Blank lines separate code into blocks.

I follow certain rules in my procedures. My principle is to use registers as often as possible. This speeds up my procedures.

15 Dec 2025, 14:06

FoXx

Joined: 25 Feb 2025
Posts: 24

FoXx 15 Dec 2025, 14:32

Useful command line splitting procedure.
Applied after the call [GetCommandLine]

Code:

;------------------------------------------------
;       * * *   Get paramameters of string
;------------------------------------------------
proc GetParamComnandLine

;       mov EDI, TableParamameters
;       mov ESI, szComnandLine

        mov EBX, EDI

.scan:
                lodsb
                cmp AL, '"'
                je skip

                cmp AL, "'"
                je skip

                        dec ESI
                        mov AL, ' '
                @@:

                mov  DL, AL
                mov EAX, ESI
                stosd

                @@:
                        lodsb
                        cmp AL, ' '
                        jb .end

                        cmp AL, DL
                        jne continue

                mov EDX, ESI
                dec ESI

                xor EAX, EAX
                mov [ESI], AL

                mov ESI, EDX

                @@:
                        lodsb
                        cmp AL, ' '
                        jb .end
                        je continue

                dec ESI
                jmp .scan

.end:
        mov ECX, EDI
        xor EAX, EAX
        stosd

        dec ESI
        mov [ESI], AL

        mov EAX, ECX
        sub EAX, EBX
        shr EAX, 2              ;       count of paramameters
        ret
endp

15 Dec 2025, 14:32

AsmGuru62

Joined: 28 Jan 2004
Posts: 1749
Location: Toronto, Canada

AsmGuru62 16 Dec 2025, 01:29

I found out the strange thing about the command line parameters.
In C language, using the double quotes preserves blanks inside of the quotes.
Everyone knows that, but what is interesting --- if there is no blank between, say, parameter #2 and parameter #3 --- the parameter includes all text.
Here is an example:

Code:

PROGRAM.EXE -param1 -param2"C:\My Files Are Here\Source.Asm"more

When PROGRAM.EXE is a C program, you get the following 2 parameters (not 3 or 4):

Code:

-param1
-param2C:\My Files Are Here\Source.Asmmore

You see?
Parameters are stuck together if you have no blanks.
Very interesting.
And I think, it is not a bug in C.
Probably done to put the flag, like "-mydir" together with actual directory name:

Code:

PROGRAM.EXE -mydir:"C:\My Files Are Here"

16 Dec 2025, 01:29

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20793
Location: In your JS exploiting you and your system

revolution 16 Dec 2025, 01:42

Quote characters are not generally considered as separators, that's what spaces are for. Quotes are used to "hide" the spaces from the tokeniser.

16 Dec 2025, 01:42

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