kolibrios-gitea/programs/demos/aclock/trunk/str2dwrd.inc

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; string2dword - a useless string to double word conversion routine
;
; Copyright (c) 2003 Thomas Mathys
; killer@vantage.ch
;
; This program is free software; you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation; either version 2 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
; GNU General Public License for more details.
;
; You should have received a copy of the GNU General Public License
; along with this program; if not, write to the Free Software
; Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
;
;********************************************************************
; converts an asciiz string into an unsigned doubleword.
; (base 10 is assumed)
;
; - first, leading whitespaces are skipped
; - then the function converts the string, until it
; finds the terminating zero, another character it
; cannot convert or the number becomes too large.
;
; input : esi = pointer to string
; output : eax = unsigned doubleword
; the function tries to convert as
; many digits as possible, before it
; stops. if the value of the dword
; becomes too large, 0xffffffff is
; returned.
; destroys : nothing
;********************************************************************
string2dword:
push ebx
push ecx
push edx
push esi
pushfd
xor ebx,ebx ; ebx : dword
; skip leading whitespaces
.skipspaces:
lodsb
cmp al,32 ; space
je .skipspaces
cmp al,12 ; ff
je .skipspaces
cmp al,10 ; lf
je .skipspaces
cmp al,13 ; cr
je .skipspaces
cmp al,9 ; ht
je .skipspaces
cmp al,11 ; vt
je .skipspaces
; convert string
dec esi ; esi -> 1st non-whitespace
.convert:
xor eax,eax ; get character
lodsb
sub al,'0' ; convert to digit
cmp al,9 ; is digit in range [0,9] ?
ja .done ; nope -> stop conversion
mov ecx,eax ; save new digit
mov eax,10 ; dword = dword * 10
mul ebx
jc .overflow
add eax,ecx ; + new digit
jc .overflow
mov ebx,eax
jmp .convert
.overflow:
mov ebx,0xffffffff
.done:
mov eax,ebx
popfd
pop esi
pop edx
pop ecx
pop ebx
ret