strlcat_PF.S

/* Copyright (c) 2006, Carlos Lamas

   based on libc/pmstring/strlcat_P.S which is
   Copyright (c) 2003, Eric B. Weddington, R. Patommel

   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__)

#if !defined(__DOXYGEN__)

#include "macros.inc"

#define dst_b1      r25
#define dst_b0      r24
#define src_b30     r23 /* ignored */
#define src_b20     r22 /* moved to src_b2 in the code */
#define src_b1      r21
#define src_b0      r20
#define siz_b1      r19
#define siz_b0      r18

#define src_b2      r28 /* must be preserved */
#define dlen_b1     src_b30
#define dlen_b0     src_b20
#define rWord_b1    r25
#define rWord_b0    r24

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

_U(strlcat_PF):

    push    src_b2
    mov src_b2, src_b20
    X_movw  XL, dst_b0      ; X = dst
    X_movw  ZL, src_b0      ; Z = src
    LPM_R0_ZPLUS_INIT src_b2

.L_strlcat_PF_dlen:         ; Find end of dst string

    ld  r0, X+          ; get next char from dst
    cp  siz_b0, __zero_reg__    ; and calc dlen = len of dst
    cpc siz_b1, __zero_reg__    ; size == 0 ?
    breq     1f         ; --> done
    tst r0          ; end of dst ?
    breq     1f         ; --> done
    subi    siz_b0, lo8(1)
    sbci    siz_b1, hi8(1)      ; siz--
    rjmp    .L_strlcat_PF_dlen  ; --> next char
1:  sbiw    XL, 1           ; undo post increment
    X_movw  dlen_b0, XL
    sub dlen_b0, dst_b0
    sbc dlen_b1, dst_b1     ; dlen = X - dst
    cp  siz_b0, __zero_reg__
    cpc siz_b1, __zero_reg__    ; size == 0 ?
    breq    .L_strlcat_PF_slen  ; --> done
    subi    siz_b0, lo8(1)
    sbci    siz_b1, hi8(1)      ; siz--

.L_strlcat_PF_concat:           ; Concatenate

    LPM_R0_ZPLUS_NEXT src_b2    ; get next char from src
    cp  siz_b0, __zero_reg__
    cpc siz_b1, __zero_reg__    ; size == 0 ?
    breq    1f          ; --> done
    tst r0          ; end of src ?
    breq    1f          ; --> done
    st  X+, r0          ; store in dest
    subi    siz_b0, lo8(1)
    sbci    siz_b1, hi8(1)      ; siz--
    rjmp    .L_strlcat_PF_concat    ; --> next char
1:  st  X, __zero_reg__     ; *X = '\0'
    sbiw    ZL, 1           ; undo post increment
#ifdef RAMPZ
    in  r0, _SFR_IO_ADDR(RAMPZ)
    sbc r0, __zero_reg__
    out _SFR_IO_ADDR(RAMPZ), r0
#endif

.L_strlcat_PF_slen:

    LPM_R0_ZPLUS_NEXT src_b2    ; get next char from src
    tst r0          ; end of src ?
    brne    .L_strlcat_PF_slen  ; --> next char
    sbiw    ZL, 1           ; undo post increment
#ifdef RAMPZ
    in  r0, _SFR_IO_ADDR(RAMPZ)
    sbc r0, __zero_reg__
    out _SFR_IO_ADDR(RAMPZ), r0
#endif
    X_movw  rWord_b0, dlen_b0
    add rWord_b0, ZL
    adc rWord_b1, ZH
    sub rWord_b0, src_b0
    sbc rWord_b1, src_b1    ; return(dlen + (Z - src))
    LPM_R0_ZPLUS_FINI src_b2
    pop src_b2
    ret

.L_strlcat_PF_end:

    .size   _U(strlcat_PF), .L_strlcat_PF_end - _U(strlcat_PF)

#endif /* not __DOXYGEN__ */

#endif /* !defined(__AVR_TINY__) */