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/* Copyright (c) 2005,2007  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: ultoa_invert.S 1944 2009-04-01 23:12:20Z arcanum $	*/

#ifndef	__DOXYGEN__

#include "macros.inc"

#include "ntz.h"

#include "xtoa_fast.h"

/* --------------------------------------------------------------------

   char * __ultoa_invert (unsigned long val, char * str, int base)

   This function is intended for usage as internal printf's one.

   It differs from others of `xtoa_fast' family:

       * srt[] will NOT 0 terminated.

       * Sequence of digits is inverted.

       * It returns pointer to first byte after a string.

       * Only `XTOA_UPPER' flag is operated.

   Notes:

       * base: check only 8 and 16, all others are treated as 10.

       (internal printf's function).

*/

    /* Input	*/

#define v_lo	r22

#define	v_hi	r23

#define	v_hlo	r24

#define	v_hhi	r25

#define	str_lo	r20

#define	str_hi	r21

#define	base	r18

#define	flags	r19

    /* Used	*/

#define	v_fifth	r26	/* val: bits 39..32			*/

#define	t_lo	r18	/* temporary for shifted `val'		*/

#define	t_hi	r19

#define	t_hlo	r20

#define	t_hhi	r21

#define	symb	r20	/* write to string			*/

#define	cnt	r27	/* shift loop counter, local arg	*/

    /* Fixed	*/

#define	rzero	r1

/*	ASSEMBLY_CLIB_SECTION */

	.global	__ultoa_invert

	.type	__ultoa_invert, "function"

__ultoa_invert:

	X_movw	ZL, str_lo

	clr	v_fifth			; needed for all (ultoa_lsr)

	cpi	base, 8

	breq	.L_oct

	cpi	base, 16

	breq	.L_hex

  ; decimal format

	clt				; flag of val == 0

.L_dec_loop:

	push	v_lo			; to calculate remander

  ; val &= ~1

	andi	v_lo, ~1

  ; val += 2

	subi	v_lo, lo8(-2)

	sbci	v_hi, hi8(-2)

	sbci	v_hlo, hlo8(-2)

	sbci	v_hhi, hhi8(-2)

	sbci	v_fifth, hhi8(-2)

  ; val += val/2

	ldi	cnt, 1

	rcall	.L_div_add

  ; val += val/16

	ldi	cnt, 4

	rcall	.L_div_add

  ; val += val/256

	add	v_lo, v_hi

	adc	v_hi, v_hlo

	adc	v_hlo, v_hhi

	adc	v_hhi, v_fifth

	adc	v_fifth, rzero

  ; val += val/65536

	add	v_lo, v_hlo

	adc	v_hi, v_hhi

	adc	v_hlo, v_fifth

	adc	v_hhi, rzero

	adc	v_fifth, rzero

  ; val += val >> 32

	add	v_lo, v_fifth

	adc	v_hi, rzero

	adc	v_hlo, rzero

	adc	v_hhi, rzero

	adc	v_fifth, rzero

  ; division result:  val /= 16

	rcall	.L_lsr_4		; v_fitth := 0

	brne	1f

	set				; T := Z flag

1:

  ; rem:  val_original - 10*val

	pop	t_hi

#if  defined(__AVR_ENHANCED__) && __AVR_ENHANCED__

	ldi	t_lo, 10

	mul	t_lo, v_lo

	clr	r1

#else

	mov	r0, v_lo

	lsl	r0

	sub	t_hi, r0

	lsl	r0

	lsl	r0

#endif

	sub	t_hi, r0

  ; output digit

	subi	t_hi, lo8(-'0')

	st	Z+, t_hi

  ; quotient == 0 ?

	brtc	.L_dec_loop

  ; end of string

.L_eos:

	X_movw	r24, ZL

	ret

  ; octal format

.L_oct:

	mov	symb, v_lo

	andi	symb, 7

	subi	symb, lo8(-'0')

	st	Z+, symb

	ldi	cnt, 3

	rcall	.L_lsr

	brne	.L_oct

	rjmp	.L_eos

  ; hex format

.L_hex:

	mov	symb, v_lo

	andi	symb, 0x0f

	subi	symb, lo8(-'0')

	cpi	symb, '9' + 1

	brlo	3f

	subi	symb, lo8('9' + 1 - 'a')

	sbrc	flags, ntz(XTOA_UPPER) - 8

	subi	symb, lo8('a' - 'A')

3:	st	Z+, symb

	rcall	.L_lsr_4

	brne	.L_hex

	rjmp	.L_eos

.L_lsr_4:

	ldi	cnt, 4

.L_lsr:

	lsr	v_fifth

	ror	v_hhi

	ror	v_hlo

	ror	v_hi

	ror	v_lo

	dec	cnt

	brne	.L_lsr

  ; tst

	sbiw	v_hlo, 0		; only Z flag is needed

	cpc	v_lo, rzero

	cpc	v_hi, rzero

	ret

.L_div_add:

  ; copy to temporary

	X_movw	t_lo, v_lo

	X_movw	t_hlo, v_hlo

	mov	r0, v_fifth

  ; lsr temporary

7:	lsr	r0

	ror	t_hhi

	ror	t_hlo

	ror	t_hi

	ror	t_lo

	dec	cnt

	brne	7b

  ; add

	add	v_lo, t_lo

	adc	v_hi, t_hi

	adc	v_hlo, t_hlo

	adc	v_hhi, t_hhi

	adc	v_fifth, r0		; here r0 == 0

	ret

	.size	__ultoa_invert, . - __ultoa_invert

	.end

#endif	/* !__DOXYGEN__ */