# strnlen_PF.S

/* Copyright (c) 2006, Carlos Lamas

based on libc/pmstring/strnlen_P.S which is

based on libc/pmstring/strnlen.S which is

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the above copyright
notice, this list of conditions and the following disclaimer in
the documentation and/or other materials provided with the
distribution.
* Neither the name of the copyright holders nor the names of
contributors may be used to endorse or promote products derived
from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
POSSIBILITY OF SUCH DAMAGE. */

/* $Id$ */

#if !defined(__AVR_TINY__)

#include "macros.inc"

#define src_b3 r25
#define src_b2 r24
#define src_b1 r23
#define src_b0 r22
#define len_b1 r21
#define len_b0 r20

/** \ingroup avr_pgmspace
\fn size_t strnlen_PF(uint_farptr_t s, size_t len)
\brief Determine the length of a fixed-size string

The strnlen_PF() function is similar to strnlen(), except that \e s is a
far pointer to a string in program space

\param s A far pointer to the string in Flash
\param len The maximum number of length to return

\returns The strnlen_PF function returns strlen_P(\e s), if that is less
than \e len, or \e len if there is no '\\0' character among the first \e
len characters pointed to by \e s. The contents of RAMPZ SFR are
undefined when the function returns */

#if !defined(__DOXYGEN__)

.text
.global _U(strnlen_PF)
.type   _U(strnlen_PF), @function

_U(strnlen_PF):

LPM_R0_ZPLUS_INIT src_b2
X_movw  ZL, src_b0

.L_strnlen_PF_loop:

LPM_R0_ZPLUS_NEXT src_b2
subi    len_b0, lo8(1)
sbci    len_b1, hi8(1)
cpse    r0, __zero_reg__
brcc    .L_strnlen_PF_loop

; RAMPZ:Z points one character past the terminating NUL
; return RAMPZ:Z - 1 - src = (-1 - src) + RAMPZ:Z = ~src + RAMPZ:Z

com     src_b0
com     src_b1