# strspn_P.S

/* Copyright (c) 2007  Dmitry Xmelkov

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. */

/* $Id$ */

/** \file */
/** \ingroup avr_pgmspace
\fn size_t strspn_P(const char *s, PGM_P accept)

The strspn_P() function calculates the length of the initial segment
of \p s which consists entirely of characters in \p accept. This
function is similar to strspn() except that \p accept is a pointer
to a string in program space.

\return  The strspn_P() function returns the number of characters in
the initial segment of \p s which consist only of characters from \p
accept. The terminating zero is not considered as a part of string. */

#if !defined(__AVR_TINY__)

#ifndef __DOXYGEN__

#include "macros.inc"

#define str_lo  r24
#define str_hi  r25
#define acc_lo  r22
#define acc_hi  r23

#define chs     r21     /* char from s[]        */

/* This realization is compact, but is not very fast: an accept string
is not cashed.       */

ASSEMBLY_CLIB_SECTION
.global _U(strspn_P)
.type   _U(strspn_P), @function

_U(strspn_P):
X_movw  XL, str_lo
; get next symbol from s[]
1:      ld      chs, X+         ; *s++
tst     chs
breq    3f
; check an occurance
X_movw  ZL, acc_lo
2:      X_lpm   r0, Z+
cp      r0, chs
cpse    r0, __zero_reg__
brne    2b
breq    1b              ; branch if chs is present in accept[]
; end of scanning: chs is not found or end of s[] is reached
; Return: X - 1 - str == X + ~str
3:      com     str_lo
com     str_hi