strspn_P.S

/* Copyright (c) 2007  Dmitry Xmelkov
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/* $Id$ */

/** \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
        add     str_lo, XL
        adc     str_hi, XH
        ret

        .size _U(strspn_P), . - _U(strspn_P)
#endif  /* !__DOXYGEN__ */

#endif /* !defined(__AVR_TINY__) */