ultoa_ncheck.S

/* Copyright (c) 2012  Georg-Johann Lay
   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 (__DOXYGEN__)
#if     !defined (__AVR_TINY__)

#include "asmdef.h"

/* char *__ultoa_ncheck (unsigned long val, char *s, unsigned char radix)
   This function is the utoa() without checking the radix for 2..36 margins.
 */

#define val_lo  r22
#define val_hi  r23
#define val_hlo r24
#define val_hhi r25
#define str_lo  r20
#define radix   r18

#define counter r19
#define digit   r26
#define sign    r27


ENTRY   __ultoa_ncheck
        clr     sign

ENTRY   __ultoa_common
        X_movw  ZL, str_lo

1:  ; Saves one iteration of the digit-loop:
    ; If val < radix we can use the low byte of val as digit
        mov     digit, val_lo
        cp      val_lo, radix
        cpc     val_hi, __zero_reg__
        cpc     val_hlo, __zero_reg__
        cpc     val_hhi, __zero_reg__
    ; now C is set, if val < radix
        sbc     counter, counter
        bst     counter, 0
        brts    4f
    ; counter == 0 here

    ; If val >= radix, then pop one digit from val
        clr     digit

2:  ; Vanilla 32:8 quotient and remainder to pop the digit
    ; digit <- val % radix
    ; val   <- val / radix
        lsl     val_lo
        rol     val_hi
        rol     val_hlo
        rol     val_hhi
        rol     digit
        cp      digit, radix
        brlo    3f
        sub     digit, radix
    ; val |= 1
        inc     val_lo
3:  ; Loop the 32 bits
        subi    counter, 8              ; 256 / 8 == 32 loops
        brne    2b

4:  ; Convert the digit to ASCII...
        subi    digit, -'0'
        cpi     digit, '9'+1
        brlo    5f
        subi    digit, '0'-'a'+10
5:  ; ... and store it to the reversed string
        st      Z+, digit

    ; Popped all digits?
        brtc    1b

    ; Yes:  Store the sign (if any)
        cpse    sign, __zero_reg__
        st      Z+, sign

    ; Terminate the string with '\0'
7:      st      Z, __zero_reg__

    ; Reverse the string and return the original string pointer
        X_movw  r24, str_lo
        XJMP    _U(strrev)

ENDFUNC

#endif  /* !__AVR_TINY__ */
#endif  /* !__DOXYGEN__ */