DIM str1$
DIM str2$
str1$ = "123456789"
str2$ = AsmLeft$(str1$, 3)
PRINT str2$
str2$ = AsmMid$(str1$, 4, 3)
PRINT str2$
str2$ = AsmMid$(str1$, 4)
PRINT str2$
str2$ = AsmRight$(str1$, 3)
PRINT str2$
FUNCTION SubStr%(SrcStr AS LPSTR, SrcStrLen%, StartPosn%, DestStr AS LPSTR, DestStrLen%)
$ASM
nop
nop
nop
;save used registers except for eax:edx
push ebx
push ecx
push edi
push esi
;load the 32-bit registers from the stack
mov esi, dword PTR [ebp+8] ;SrcStr
mov edx, dword PTR [ebp+12] ;SrcLen
mov eax, dword PTR [ebp+16] ;StartPosn
mov edi, dword PTR [ebp+20] ;DestStr
mov ecx, dword PTR [ebp+24] ;DestLen
;check for zero-length Destination string
jecxz NoGood
;compensate StartPosn for 0 based count
dec eax
;check for negative offset of StartPosn
cmp eax, 0
jl NoGood
;point esi to start of SrcStr
add esi, eax
;and subtract StartPosn from SrcLen
sub edx, eax
;check if offset is past end of SrcStr
cmp edx, 0
jle NoGood
;move substring of esi into edi
rep movsb
;return this to indicate function worked
mov eax, edi
jmp ReturnAX
NoGood:
mov eax, -1
ReturnAX:
pop esi
pop edi
pop ecx
pop ebx
pop ebp
ret
$ASM
FUNCTION = 0
END FUNCTION
'Left$ equivalent
FUNCTION AsmLeft$(fnstr1$, fnint1%)
DIM RAW startp% = 1
DIM RAW retstr$ * fnint1% + 256
SubStr(fnstr1$, LEN(fnstr1$), startp%, retstr$, fnint1%)
retstr[fnint1] = 0
FUNCTION = retstr$
END FUNCTION
'MID$ equivalent
FUNCTION AsmMid$ OPTIONAL(fnstr1$, fnint1%, fnint2%=0)
DIM RAW startp% = fnint1%
DIM RAW lenfnstr1% = LEN(fnstr1$)
DIM RAW retstr$ * fnint2% + 256
IF fnint2% = 0 THEN
fnint2% = lenfnstr1% - startp% + 1
END IF
SubStr(fnstr1$, lenfnstr1%, startp%, retstr$, fnint2%)
retstr[fnint2] = 0
FUNCTION = retstr$
END FUNCTION
'RIGHT$ equivalent
FUNCTION AsmRight$(fnstr1$, fnint1%)
DIM RAW lenfnstr1% = LEN(fnstr1$)
DIM RAW startp% = lenfnstr1% - fnint1% + 1
DIM RAW retstr$ * fnint1% + 256
SubStr(fnstr1$, lenfnstr1%, startp%, retstr$, fnint1%)
retstr[fnint1] = 0
FUNCTION = retstr$
END FUNCTION
Poll