# strlcat.S

/*
AVR LIBC
strlcat()

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

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_string
\fn size_t strlcat (char *dst, const char *src, size_t siz)
\brief Concatenate two strings.

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() 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
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:      ld      __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:   ld      __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