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.

*/

/* $Id$ */

/** \ingroup avr_pgmspace
    \fn size_t strlcat_PF (char *dst, uint_farptr_t src, size_t n)
    \brief Concatenate two strings

    The strlcat_PF() function is similar to strlcat(), except that the \e src
    string must be located in program space (flash) and is addressed using
        a far pointer

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

    \param dst A pointer to the destination string in SRAM
    \param src A far pointer to the source string in Flash
    \param n The total number of bytes allocated to the destination string

    \returns The strlcat_PF() function returns strlen(\e src) + MIN(\e n,
    strlen(initial \e dst)).  If retval >= \e n, truncation occurred. The
    contents of RAMPZ SFR are undefined when the funcion returns */

#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__) */