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;--------------------------------------------------------------------------
; 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
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