strncasecmp_P.S

/* Copyright (c) 2002, 2005, 2006, 2007 Reiner Patommel
   Copyright (c) 2007  Dmitry Xmelkov
   All rights reserved.

   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. */

/* $Id$ */

/*
   strncasecmp_P.S
   Case insensitive compare

   Contributors:
     Created by Reiner Patommel
*/
/** \file */

/** \ingroup avr_pgmspace
    \fn int strncasecmp_P(const char *s1, PGM_P s2, size_t n)
    \brief Compare two strings ignoring case.

    The strncasecmp_P() function is similar to strcasecmp_P(), except it
    only compares the first \p n characters of \p s1.

    \param s1 A pointer to a string in the devices SRAM.
    \param s2 A pointer to a string in the devices Flash.
    \param n The maximum number of bytes to compare.

    \returns The strncasecmp_P() function returns an integer less than,
    equal to, or greater than zero if \p s1 (or the first \p n bytes
    thereof) is found, respectively, to be less than, to match, or be
    greater than \p s2. A consequence of the ordering used by
    strncasecmp_P() is that if \p s1 is an initial substring of \p s2,
    then \p s1 is considered to be "less than" \p s2.  */


#if !defined(__AVR_TINY__)

#if !defined(__DOXYGEN__)

#include "macros.inc"

#define s1_hi r25
#define s1_lo r24
#define s2_hi r23
#define s2_lo r22
#define len_hi r21
#define len_lo r20

#define tmp    r22
#define ret_hi r25
#define ret_lo r24

        ASSEMBLY_CLIB_SECTION
        .global _U(strncasecmp_P)
        .type   _U(strncasecmp_P), @function
_U(strncasecmp_P):
        X_movw  ZL, s2_lo
        X_movw  XL, s1_lo

1:      subi    len_lo, lo8(1)          ; if (--len == -1) return 0
        sbci    len_hi, hi8(1)
        brlo    5f

        ld      ret_lo, X+              ; *s1++
        cpi     ret_lo, 'A'             ; if in [A-Z] then tolower()
        brlt    2f
        cpi     ret_lo, 'Z'+1
        brge    2f
        subi    ret_lo, 'A'-'a'

2:      X_lpm   tmp, Z+                 ; *s2++
        cpi     tmp, 'A'                ; if in [A-Z] then tolower()
        brlt    3f
        cpi     tmp, 'Z'+1
        brge    3f
        subi    tmp, 'A'-'a'

3:      sub     ret_lo, tmp             ; compare
        cpse    tmp, __zero_reg__       ; break, if end of string
        breq    1b
4:      sbc     ret_hi, ret_hi          ; sign extension
        ret

5:      sub     ret_lo, ret_lo          ; length limit, return 0
        rjmp    4b

        .size   _U(strncasecmp_P), . - _U(strncasecmp_P)

#endif /* not __DOXYGEN__ */

#endif /* !defined(__AVR_TINY__) */