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/* Copyright (c) 2005, 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: ftoa_engine.S,v 1.3 2009/04/01 23:11:00 arcanum Exp $ */

#ifndef	__DOXYGEN__

#include "macros.inc"

#include "ftoa_engine.h"

#if  defined(__AVR_HAVE_LPMX__) && __AVR_HAVE_LPMX__

#  define AVR_ENH_LPM	1

#else

#  define AVR_ENH_LPM	0

#endif

/*

   int __ftoa_engine (double val, char *buf,

                      unsigned char prec, unsigned char maxdgs)

 Input:

    val    - value to convert

    buf    - output buffer address

    prec   - precision: number of decimal digits is 'prec + 1'

    maxdgs - (0 if unused) precision restriction for "%f" specification

 Output:

    return     - decimal exponent of first digit

    buf[0]     - flags (FTOA_***)

    buf[1],... - decimal digits

    Number of digits:

	maxdgs == 0 ? prec+1 :

	(buf[0] & FTOA_CARRY) == 0 || buf[1] != '1' ?

	    aver(1, maxdgs+exp, prec+1) :

	    aver(1, masdgs+exp-1, prec+1)

 Notes:

    * Output string is not 0-terminated. For possibility of user's buffer

    usage in any case.

    * If used, 'maxdgs' is a number of digits for value with zero exponent.

*/

    /* Input */

#define maxdgs	r16

#define	prec	r18

#define	buf_lo	r20

#define	buf_hi	r21

#define	val_lo	r22

#define	val_hi	r23

#define	val_hlo	r24

#define	val_hhi	r25

    /* Float value parse	*/

#define	flag	r19

    /* Multiplication of mantisses	*/

#define	exp_sv	r17

#define	mlt_1	r19	/* lowest result byte	*/

#define mlt_2	r14

#define	mlt_3	r15

#define	mlt_4	r20

#define	mlt_5	r21

#define	mlt_6	r28

#define	mlt_7	r29

    /* Conversion to string	*/

#define	pwr_2	r1	/* lowest byte of 'powr10' element	*/

#define	pwr_3	r17

#define	pwr_4	r19

#define	pwr_5	r22

#define	pwr_6	r25

#define	pwr_7	r0

#define	digit	r23

#define	exp10	r24

    /* Fixed */

#define	zero	r1

/*    ASSEMBLY_CLIB_SECTION */

    .global	__ftoa_engine

    .type	__ftoa_engine, "function"

__ftoa_engine:

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

   Float value parse.

*/

  ; limit 'prec'

	cpi	prec, 8

	brlo	1f

	ldi	prec, 7

1:

  ; init.

	clr	flag

	X_movw	XL, buf_lo

  ; val_hhi := exponent, sign test and remove

#if  FTOA_MINUS != 1

#  error  FTOA_MINUS must be 1:  add with carry used

#endif

	lsl	val_hhi

	adc	flag, zero		; FTOA_MINUS

	sbrc	val_hlo, 7

	ori	val_hhi, 1

  ; zero test

	adiw	val_hlo, 0

	cpc	val_lo, zero

	cpc	val_hi, zero

	brne	3f

  ; return 0

	ori	flag, FTOA_ZERO

	subi	prec, -2

2:	st	X+, flag

	ldi	flag, '0'

	dec	prec

	brne	2b

	ret				; r24,r25 == 0

3:

  ; infinity, NaN ?

#if  FTOA_NAN != 2 * FTOA_INF

#  error  Must: FTOA_NAN == 2*FTOA_INF: 'rjmp' is absent

#endif

	cpi	val_hhi, 0xff

	brlo	6f

	cpi	val_hlo, 0x80

	cpc	val_hi, zero

	cpc	val_lo, zero

	breq	5f

	subi	flag, -FTOA_INF		; FTOA_NAN

5:	subi	flag, -FTOA_INF

6:

  ; write flags byte

	st	X+, flag

  ; hidden bit

	cpi	val_hhi, 1

	brlo	7f			; if subnormal value

	ori	val_hlo, 0x80

7:	adc	val_hhi, zero

  ; pushes

	push	r29

	push	r28

	push	r17

	push	r16

	push	r15

	push	r14

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

   Multiplication of mantisses (val and table).

   At the begin:

	val_hlo .. val_lo  - input value mantisse

	val_hhi            - input value exponent

	X                  - second byte address (string begin)

   At the end:

	mlt_7 .. mlt_2     - multiplication result

	exp10              - decimal exponent

*/

  ; save

	mov	exp_sv, val_hhi

  ; Z := & base10[exp / 8]	(sizeof(base10[0]) == 5)

	andi	val_hhi, ~7

	lsr	val_hhi			; (exp/8) * 4

	mov	ZL, val_hhi

	lsr	val_hhi

	lsr	val_hhi			; exp/8

	add	ZL, val_hhi		; (exp/8) * 5

	clr	ZH

	subi	ZL, lo8(-(.L_base10))

	sbci	ZH, hi8(-(.L_base10))

  ; highest mantissa byte  (mult. shifting prepare)

	clr	val_hhi

  ; result initializ.

	clr	mlt_1

	clr	mlt_2

	clr	mlt_3

	X_movw	mlt_4, mlt_2

	X_movw	mlt_6, mlt_2

  ; multiply to 1-st table byte

#if  AVR_ENH_LPM

	lpm	r0, Z+

#else

	lpm

	adiw	ZL, 1

#endif

	sec			; for loop end control

	ror	r0

  ; addition

10:	brcc	11f

	add	mlt_1, val_lo

	adc	mlt_2, val_hi

	adc	mlt_3, val_hlo

	adc	mlt_4, val_hhi

	adc	mlt_5, zero

  ; arg shift

11:	lsl	val_lo

	rol	val_hi

	rol	val_hlo

	rol	val_hhi

  ; next bit

	lsr	r0

	brne	10b

  ; second table byte

#if  AVR_ENH_LPM

	lpm	r0, Z+		; C flag is stay 1

#else

	lpm

	adiw	ZL, 1

	sec

#endif

	ror	r0

  ; addition

12:	brcc	13f

	add	mlt_2, val_hi		; val_hi is the least byte now

	adc	mlt_3, val_hlo

	adc	mlt_4, val_hhi

	adc	mlt_5, val_lo

	adc	mlt_6, zero

  ; arg shift

13:	lsl	val_hi

	rol	val_hlo

	rol	val_hhi

	rol	val_lo

  ; next bit

	lsr	r0

	brne	12b

  ; 3-t table byte

#if  AVR_ENH_LPM

	lpm	r0, Z+		; C flag is stay 1

#else

	lpm

	adiw	ZL, 1

	sec

#endif

	ror	r0

  ; addition

14:	brcc	15f

	add	mlt_3, val_hlo		; val_hlo is the least byte now

	adc	mlt_4, val_hhi

	adc	mlt_5, val_lo

	adc	mlt_6, val_hi

	adc	mlt_7, zero

  ; arg shift

15:	lsl	val_hlo

	rol	val_hhi

	rol	val_lo

	rol	val_hi

  ; next bit

	lsr	r0

	brne	14b

  ; 4-t table byte

#if  AVR_ENH_LPM

	lpm	r0, Z+		; C flag is stay 1

#else

	lpm

#endif

	ror	r0

  ; addition

16:	brcc	17f

	add	mlt_4, val_hhi		; val_hhi is the least byte now

	adc	mlt_5, val_lo

	adc	mlt_6, val_hi

	adc	mlt_7, val_hlo

  ; arg shift

17:	lsl	val_hhi

	rol	val_lo

	rol	val_hi

	rol	val_hlo

  ; next bit

	lsr	r0

	brne	16b

  ; decimal exponent

#if  AVR_ENH_LPM

	lpm	exp10, Z

#else

	adiw	ZL, 1

	lpm

	mov	exp10, r0

#endif

  ; result shift:  mlt_7..2 >>= (~exp & 7)

	com	exp_sv

	andi	exp_sv, 7

	breq	19f

18:	lsr	mlt_7

	ror	mlt_6

	ror	mlt_5

	ror	mlt_4

	ror	mlt_3

	ror	mlt_2

	dec	exp_sv

	brne	18b

19:

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

   Conversion to string.

   Registers usage:

      mlt_7 .. mlt_2	- new mantissa (multiplication result)

      pwr_7 .. pwr_2	- 'powr10' table element

      Z			- 'powr10' table pointer

      X			- output string pointer

      maxdgs		- number of digits

      prec		- number of digits stays to output

      exp10		- decimal exponent

      digit		- conversion process

   At the end:

      X			- end of buffer (nonfilled byte)

      exp10		- corrected dec. exponent

      mlt_7 .. mlt_2	- remainder

      pwr_7 .. pwr_2	- last powr10[] element

   Notes:

     * It is possible to leave out powr10'x table with subnormal value.

      Result: accuracy degrease on the rounding phase.  No matter: high

      precision with subnormals is not needed. (Now 0x00000001 is converted

      exactly on prec = 5, i.e. 6 digits.)

*/

  ; to find first digit

	ldi	ZL, lo8(.L_powr10)

	ldi	ZH, hi8(.L_powr10)

	set

  ; 'pwr10' element reading

.L_digit:

	X_lpm	pwr_2, Z+

	X_lpm	pwr_3, Z+

	X_lpm	pwr_4, Z+

	X_lpm	pwr_5, Z+

	X_lpm	pwr_6, Z+

	X_lpm	pwr_7, Z+

  ; 'digit' init.

	ldi	digit, '0' - 1

  ; subtraction loop

20:	inc	digit

	sub	mlt_2, pwr_2

	sbc	mlt_3, pwr_3

	sbc	mlt_4, pwr_4

	sbc	mlt_5, pwr_5

	sbc	mlt_6, pwr_6

	sbc	mlt_7, pwr_7

	brsh	20b

  ; restore mult

	add	mlt_2, pwr_2

	adc	mlt_3, pwr_3

	adc	mlt_4, pwr_4

	adc	mlt_5, pwr_5

	adc	mlt_6, pwr_6

	adc	mlt_7, pwr_7

  ; analisys

	brtc	25f

	cpi	digit, '0'

	brne	21f		; this is the first digit finded

	dec	exp10

	rjmp	.L_digit

  ; now is the first digit

21:	clt

  ; number of digits

	subi	maxdgs, 1

	brlo	23f			; maxdgs was 0

	add	maxdgs, exp10

	brpl	22f

	clr	maxdgs

22:	cp	maxdgs, prec

	brsh	23f

	mov	prec, maxdgs

23:	inc	prec

	mov	maxdgs, prec

  ; operate digit

25:	cpi	digit, '0' + 10

	brlo	27f

  ; overflow, digit > '9'

	ldi	digit, '9'

26:	st	X+, digit

	dec	prec

	brne	26b

	rjmp	.L_up

  ; write digit

27:	st	X+, digit

	dec	prec

	brne	.L_digit

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

    Rounding.

*/

.L_round:

  ; pwr10 /= 2

	lsr	pwr_7

	ror	pwr_6

	ror	pwr_5

	ror	pwr_4

	ror	pwr_3

	ror	pwr_2

  ; mult -= pwr10  (half of last 'pwr10' value)

	sub	mlt_2, pwr_2

	sbc	mlt_3, pwr_3

	sbc	mlt_4, pwr_4

	sbc	mlt_5, pwr_5

	sbc	mlt_6, pwr_6

	sbc	mlt_7, pwr_7

  ; rounding direction?

	brlo	.L_rest

  ; round to up

.L_up:

	inc	prec

	ld	digit, -X

	inc	digit

	cpi	digit, '9' + 1

	brlo	31f

	ldi	digit, '0'

31:	st	X, digit

	cpse	prec, maxdgs

	brsh	.L_up

  ; it was a carry to master digit

	ld	digit, -X		; flags

	ori	digit, FTOA_CARRY	; 'C' is not changed

	st	X+, digit

	brlo	.L_rest			; above comparison

  ; overflow

	inc	exp10

	ldi	digit, '1'

32:	st	X+, digit

	ldi	digit, '0'

	dec	prec

	brne	32b

  ; restore

.L_rest:

	clr	zero

	pop	r14

	pop	r15

	pop	r16

	pop	r17

	pop	r28

	pop	r29

  ; return

	clr	r25

	sbrc	exp10, 7		; high byte

	com	r25

	ret

    .size  __ftoa_engine, . - __ftoa_engine

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

    Tables.  '.L_powr10' is placed first -- for subnormals stability.

*/

    .section .progmem.data,"a",@progbits

    .type .L_powr10, "object"

.L_powr10:

	.byte	0, 64, 122, 16, 243, 90	; 100000000000000

	.byte	0, 160, 114, 78, 24, 9	; 10000000000000

	.byte	0, 16, 165, 212, 232, 0	; 1000000000000

	.byte	0, 232, 118, 72, 23, 0	; 100000000000

	.byte	0, 228, 11, 84, 2, 0	; 10000000000

	.byte	0, 202, 154, 59, 0, 0	; 1000000000

	.byte	0, 225, 245, 5, 0, 0	; 100000000

	.byte	128, 150, 152, 0, 0, 0	; 10000000

	.byte	64, 66, 15, 0, 0, 0	; 1000000

	.byte	160, 134, 1, 0, 0, 0	; 100000

	.byte	16, 39, 0, 0, 0, 0	; 10000

	.byte	232, 3, 0, 0, 0, 0	; 1000

	.byte	100, 0, 0, 0, 0, 0	; 100

	.byte	10, 0, 0, 0, 0, 0	; 10

	.byte	1, 0, 0, 0, 0, 0	; 1

    .size .L_powr10, . - .L_powr10

    .type	.L_base10, "object"

.L_base10:

	.byte	44, 118, 216, 136, -36	; 2295887404

	.byte	103, 79, 8, 35, -33	; 587747175

	.byte	193, 223, 174, 89, -31	; 1504632769

	.byte	177, 183, 150, 229, -29	; 3851859889

	.byte	228, 83, 198, 58, -26	; 986076132

	.byte	81, 153, 118, 150, -24	; 2524354897

	.byte	230, 194, 132, 38, -21	; 646234854

	.byte	137, 140, 155, 98, -19	; 1654361225

	.byte	64, 124, 111, 252, -17	; 4235164736

	.byte	188, 156, 159, 64, -14	; 1084202172

	.byte	186, 165, 111, 165, -12	; 2775557562

	.byte	144, 5, 90, 42, -9	; 710542736

	.byte	92, 147, 107, 108, -7	; 1818989404

	.byte	103, 109, 193, 27, -4	; 465661287

	.byte	224, 228, 13, 71, -2	; 1192092896

	.byte	245, 32, 230, 181, 0	; 3051757813

	.byte	208, 237, 144, 46, 3	; 781250000

	.byte	0, 148, 53, 119, 5	; 2000000000

	.byte	0, 128, 132, 30, 8	; 512000000

	.byte	0, 0, 32, 78, 10	; 1310720000

	.byte	0, 0, 0, 200, 12	; 3355443200

	.byte	51, 51, 51, 51, 15	; 858993459

	.byte	152, 110, 18, 131, 17	; 2199023256

	.byte	65, 239, 141, 33, 20	; 562949953

	.byte	137, 59, 230, 85, 22	; 1441151881

	.byte	207, 254, 230, 219, 24	; 3689348815

	.byte	209, 132, 75, 56, 27	; 944473297

	.byte	247, 124, 29, 144, 29	; 2417851639

	.byte	164, 187, 228, 36, 32	; 618970020

	.byte	50, 132, 114, 94, 34	; 1584563250

	.byte	129, 0, 201, 241, 36	; 4056481921

	.byte	236, 161, 229, 61, 39	; 1038459372

    .size .L_base10, . - .L_base10

	.end

#endif	/* !__DOXYGEN__ */