strncat_P.S

/* Copyright (c) 2003, 2005, 2006, 2007 Reiner Patommel
   based on strncat by 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. */

/* $Id$ */

/** \file */
/** \ingroup avr_pgmspace
    \fn char *strncat_P(char *dest, PGM_P src, size_t len)
    \brief Concatenate two strings.

    The strncat_P() function is similar to strncat(), except that the \e src
    string must be located in program space (flash).

    \returns The strncat_P() function returns a pointer to the resulting string
    dest.  */

#if !defined(__AVR_TINY__)

#if !defined(__DOXYGEN__)

#include "macros.inc"

#define dest_hi r25
#define dest_lo r24
#define src_hi r23
#define src_lo r22
#define len_hi r21
#define len_lo r20

        ASSEMBLY_CLIB_SECTION
        .global _U(strncat_P)
        .type   _U(strncat_P), @function
        
_U(strncat_P):
        X_movw  ZL, src_lo
        X_movw  XL, dest_lo
.L_strncat_P_skip:
        ld      __tmp_reg__, X+
        tst     __tmp_reg__
        brne    .L_strncat_P_skip
        sbiw    XL, 1           ; undo post-increment (point the the NUL)
.L_strncat_P_loop:
        subi    len_lo, lo8(1)
        sbci    len_hi, hi8(1)
        brcs    .L_strncat_P_done
        X_lpm   r0, Z+
        tst     r0
        st      X+, r0
        brne    .L_strncat_P_loop
; return dest (unchanged)
        ret
.L_strncat_P_done:
        st      X, __zero_reg__
; return dest (unchanged)
        ret
.L_strncat_P_end:
        .size   _U(strncat_P), .L_strncat_P_end - _U(strncat_P)

#endif /* not __DOXYGEN__ */

#endif /* !defined(__AVR_TINY__) */