strcmp_PF.S

/* Copyright (c) 2006, Carlos Lamas

   based on libc/pmstring/strcmp_P.S which is
   Copyright (c) 2002, Marek Michalkiewicz

   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. */

/* $Id$ */

#if !defined(__AVR_TINY__)

#include "macros.inc"

#define s1_b1 r25
#define s1_b0 r24
#define s2_b3 r23
#define s2_b2 r22
#define s2_b1 r21
#define s2_b0 r20

#define ret_b1 r25
#define ret_b0 r24

/** \ingroup avr_pgmspace
    \fn int strcmp_PF (const char *s1, uint_farptr_t s2)
        \brief Compares two strings

    The strcmp_PF() function is similar to strcmp() except that \e s2 is a far
    pointer to a string in program space

    \param s1 A pointer to the first string in SRAM
    \param s2 A far pointer to the second string in Flash

    \returns The strcmp_PF() function returns an integer less than, equal to,
    or greater than zero if \e s1 is found, respectively, to be less than, to
    match, or be greater than \e s2. The contents of RAMPZ SFR are undefined
    when the function returns */

#if !defined(__DOXYGEN__)

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

_U(strcmp_PF):

        X_movw  ZL, s2_b0
        LPM_R0_ZPLUS_INIT s2_b2
        X_movw  XL, s1_b0

.L_strcmp_PF_loop:

        ld      ret_b0, X+
        LPM_R0_ZPLUS_NEXT s2_b2
        sub     ret_b0, r0
        brne    .L_strcmp_PF_done
        tst     r0
        brne    .L_strcmp_PF_loop

.L_strcmp_PF_done:
; ret_hi = SREG.C ? 0xFF : 0

        sbc     ret_b1, ret_b1
        LPM_R0_ZPLUS_FINI s2_b2
        ret

.L_strcmp_PF_end:

        .size   _U(strcmp_PF), .L_strcmp_PF_end - _U(strcmp_PF)

#endif /* not __DOXYGEN__ */

#endif /* !defined(__AVR_TINY__) */