strlcat_P.S

/*
   AVR LIBC
   strlcat_P()

   Copyright (c) 2003, 2005, 2006, 2007 Eric B. Weddington, R. Patommel
   Copyright (c) 2009  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.

*/

/* $Id$ */

/** \file */

/** \ingroup avr_pgmspace
    \fn size_t strlcat_P (char *dst, PGM_P src, size_t siz)
    \brief Concatenate two strings.

    The strlcat_P() function is similar to strlcat(), except that the \p src
    string must be located in program space (flash).

    Appends \p src to string \p dst of size \p siz (unlike strncat(),
    \p siz is the full size of \p dst, not space left).  At most \p siz-1
    characters will be copied.  Always NULL terminates (unless \p siz <=
    \p strlen(dst)).

    \returns The strlcat_P() function returns strlen(src) + MIN(siz,
    strlen(initial dst)).  If retval >= siz, truncation occurred.       */


#if !defined(__AVR_TINY__)

#if !defined(__DOXYGEN__)

#include "asmdef.h"

/*  size_t strlcat (char *dst, const char *src, size_t siz)
    {
        char *d = dst;
        const char *s = src;

        do {
            if (--siz == ~0u)
                goto Len;                       // siz <= strlen(dst)
        } while (*d++);
        d -= 1;

        goto m;
        do {
            if (!(*d++ = *s++))
                return (d - dst - 1);           // normal end
          m: ;
        } while (--siz != ~0u);
        *d = 0;

      Len:
        return (d - dst + strlen (s));
    }
 */

#define dst_lo  r24
#define dst_hi  r25
#define src_lo  r22
#define src_hi  r23
#define siz_lo  r20
#define siz_hi  r21
#define ret_lo  r24

ENTRY strlcat_P
        X_movw  XL, dst_lo              ; X = dst
        X_movw  ZL, src_lo              ; Z = src

  ; find end of dst: X := dst + strlen(dsr)
1:      subi    siz_lo, lo8(1)
        sbci    siz_hi, hi8(1)
        brlo    .Len                    ; siz <= strlen(dst)
        ld      __tmp_reg__, X+
        tst     __tmp_reg__
        brne    1b
        sbiw    XL, 1
        rjmp    3f

  ; copy loop
2:      X_lpm   __tmp_reg__, Z+
        st      X+, __tmp_reg__
        tst     __tmp_reg__
        breq    .Ldd
3:      subi    siz_lo, lo8(1)
        sbci    siz_hi, hi8(1)
        brsh    2b
        st      X, __zero_reg__

  ; return (d - dst + strlen(s))
        X_movw  src_lo, ZL              ; update for strlen(s) calculation
.Len:   X_lpm   __tmp_reg__, Z+         ; find end of src
        tst     __tmp_reg__
        brne    .Len
        sub     ZL, src_lo              ; Z := strlen(s) + 1
        sbc     ZH, src_hi
        add     XL, ZL                  ; d += strlen(s) + 1
        adc     XH, ZH
.Ldd:   sec                             ; d -= dst + 1
        sbc     XL, dst_lo
        sbc     XH, dst_hi
        X_movw  ret_lo, XL              ; return value
        ret

ENDFUNC

#endif /* not __DOXYGEN__ */

#endif /* !defined(__AVR_TINY__) */