PBWin ASM MyVal() - Optimized for special case

[Bern Ertl]

#COMPILE EXE
#DIM ALL

FUNCTION MyVal( sSource AS STRING) AS LONG

	'Assumes sSource contains only characters from "0" to "9" and %MaxLong >= VAL( sSource) >= 0

	#REGISTER NONE
	LOCAL psSource AS LONG

	psSource = STRPTR( sSource)

	!mov   esi, psSource
	!mov   ecx, [esi-4]      ; get size of string data

	!xor   eax, eax          ; clear EAX
	!xor   ebx, ebx          ; clear EBX
	!mov   edi, 10           ; base 10

	!test  ecx, ecx
	!jz    Done

NextChar:
	!mov   bl, [esi]         ; get a character
	!mul   edi               ; eax = eax * 10
	!sub   bl, 48            ; convert character to binary digit
	!add   eax, ebx          ; add in the digit
	!inc   esi
	!dec   ecx
	!jnz   NextChar

Done:
	!mov   FUNCTION, eax

END FUNCTION

%NumTests = 1000000

FUNCTION PBMAIN() AS LONG

	LOCAL a$, I AS LONG, J AS LONG
	LOCAL qValTix AS QUAD, qMyValTix AS QUAD

	RANDOMIZE TIMER

	'Does it work?
	DO
		a$ = FORMAT$( RND( 0, 2147483647&))
		I = MyVal(a$)
	LOOP UNTIL MSGBOX( "a$ = " + $DQ + a$ + $DQ + $CRLF + $CRLF + "MyVal( a$) = " + FORMAT$( I) + $CRLF + $CRLF + "Test again?", %MB_ICONQUESTION OR %MB_YESNO, "MyVal") = %IDNO

	'Benchmarking...
	DO
		a$ = FORMAT$( RND( 0, 2147483647&))

		TIX qValTix
		FOR J = 1 TO %NumTests
			I = VAL(a$)
			I = VAL(a$)
			I = VAL(a$)
		NEXT
		TIX END qValTix

		TIX qMyValTix
		FOR J = 1 TO %NumTests
			I = MyVal(a$)
			I = MyVal(a$)
			I = MyVal(a$)
		NEXT
		TIX END qMyValTix

	LOOP UNTIL MSGBOX( "VAL() took " + FORMAT$( qValTix, "#,") + " tix." + $CRLF + $CRLF + "MyVal() took " + FORMAT$( qMyValTix, "#,") + " tix." + $CRLF + $CRLF + "Test again?", %MB_ICONQUESTION OR %MB_YESNO, "MyVal") = %IDNO

END FUNCTION