Subversion Repositories NedoOS

;--------------------------------------------------------------------------
;  strlen.s
;
;  Copyright (C) 2008-2009, Philipp Klaus Krause
;
;  This library 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, or (at your option) any
;  later version.
;
;  This library 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 library; see the file COPYING. If not, write to the
;  Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
;   MA 02110-1301, USA.
;
;  As a special exception, if you link this library with other files,
;  some of which are compiled with SDCC, to produce an executable,
;  this library does not by itself cause the resulting executable to
;  be covered by the GNU General Public License. This exception does
;  not however invalidate any other reasons why the executable file
;   might be covered by the GNU General Public License.
;--------------------------------------------------------------------------

        .area   _CODE

        .globl _strlen

; The Z80 has the cpir instruction, which is perfect for implementing strlen().

_strlen:
        pop     bc
        pop     hl
        push    hl
        push    bc
        xor     a, a
        ld      b, a
        ld      c, a
        cpir
        ld      hl, #-1
        sbc     hl, bc  ; C flag still cleared from xor above.
        ret