Subversion Repositories NedoOS

#ifndef included_f32toa

#define included_f32toa

#include "pushpop.z80"

#include "f32_pow10_LUT.z80"

#include "f32mul.z80"

#include "mov4.z80"

#include "common_str.z80"

;#define EXTERNAL_FORMAT_LEN                  ;Uses an external reference to get the format length

;#define EXTERNAL_FORMAT_LEN fmtDigits    ;Use for TI-OS

; Set a hard upper limit to the number of digits used

; This routine uses at most MAX_FORMAT_LEN+8 bytes of space

#ifndef MAX_FORMAT_LEN

#define MAX_FORMAT_LEN 8

#endif

; Set the default number of digits used. If EXTERNAL_FORMAT_LEN is defined and

; that value is 0 or greater than MAX_FORMAT_LEN, then FORMAT_LEN is used.

#ifndef FORMAT_LEN

#define FORMAT_LEN 6

#endif

; set the char to use for `e` notation

#ifndef TOK_ENG

#define TOK_ENG 'e'

#endif

; set the char to use for negatives

#ifndef TOK_NEG

#define TOK_NEG '-'

#endif

; set the char to use for decimal points

#ifndef TOK_DECIMAL

#define TOK_DECIMAL '.'

#endif

#define f32toa_x    scrap

f32toa:

;Inputs:

;   HL points to the input float

;   BC points to where the string gets written.

  call pushpop

  ld e,(hl)

  inc hl

  ld d,(hl)

  inc hl

  ld (f32toa_x),de

  ld a,(hl)

  ld e,a

  add a,a

  inc hl

  ld a,(hl)

  ld d,a

  adc a,a

  ld h,b

  ld l,c

  inc a

  jp z,f32toa_return_infnan

  res 7,d

  ld (f32toa_x+2),de

  jr nc,+_

  ld (hl),TOK_NEG    ;negative sign

  inc hl

_:

;DEBC is the float, A is a copy of the exponent, HL points to the next byte to write

  dec a

  jp z,f32toa_return_0

  push hl

  ld (hl),'0' ; pad one more '0' to make room for rounding (i.e. 9.999999=>10.000000)

  inc hl

  push hl

; approximate the base-10 exponent as floor((A-127)*log10(2))

; which is approximately floor((A-127)*77/256)

  ld h,0

  ld l,a

  ld b,h

  ld c,a

  add hl,hl ;2

  add hl,hl ;4

  add hl,hl ;8

  add hl,bc ;9

  add hl,hl ;18

  add hl,bc ;19

  add hl,hl ;38

  add hl,hl ;76

  add hl,bc ;77

  ; now subtract 127*77 from HL and keep the upper 8 bits of the result

  ld a,205

  add a,l

  ld a,217

  adc a,h

  ; A is the approximate base-10 exponent

;f32toa_x needs to be multipled by 10^-A

  push af ; save the exponent

  call nz,f32toa_adjust

;the float is now on [1, 20)

;Let's no work on the float as a 0.24 fixed-point value

;we'll first need to extract the integer component

  ld hl,(f32toa_x)

  ld de,(f32toa_x+2)

  ld a,e

  rlca

  scf

  rra

  ld e,a

  ld a,d

  adc a,a

  sub 126

; A is how many bits to shift out of HLE

  ld b,a

  xor a

f32toa_first_digit_loop:

  add hl,hl

  rl e

  rla

  djnz f32toa_first_digit_loop

; A is the first digit

  pop bc  ; B is the base-10 exponent

  ex (sp),hl

  ld d,0

  cp 10

  jr c,f32toa_first_digit_fixed

  inc d

  dec hl

  ld (hl),'1'

  inc hl

  sub 10

f32toa_first_digit_fixed:

  add a,'0'

  ld (hl),a

  ld a,b

  ex (sp),hl

  pop bc

;A is the base-10 exponent

;BC is where to write the digits

;EHL is the 0.24 fixed-point number

;D is 1 if we have 2 digits already, else D is 0

  push af

  call f32toa_digits

;BC points to the last digit. We'll want to round!

  ld h,b

  ld l,c

  ld a,(hl)

  ld (hl),0

  add a,5

  jr f32toa_round_start

f32toa_round_loop:

  dec hl

  inc (hl)

  ld a,(hl)

f32toa_round_start:

  cp '9'+1

  jr nc,f32toa_round_loop

; the string is rounded

  inc hl

  ld (hl),0

  ; pop the exponent off the stack and sign-extend

  pop af

  ld e,a

  add a,a

  sbc a,a

  ld d,a

  pop hl

  ; check if rounding caused overflow; increment exponent if so

  ld a,(hl)

  cp '0'

  jp z,formatstr

  inc de

  jp formatstr

f32toa_digits:

; How many digits do we need?

#ifdef EXTERNAL_FORMAT_LEN

  ; we define the number of digits externally

  ld a,(EXTERNAL_FORMAT_LEN)

  ; if A is 0, use FORMAT_LEN

  or a

  jr nz,$+4

  ld a,FORMAT_LEN

  ; if A > MAX_FORMAT_LEN, set A to MAX_FORMAT_LEN

  cp MAX_FORMAT_LEN

  jr c,$+4

  ld a,MAX_FORMAT_LEN

  ; the first digit is written.

  ; if we only wanted 1 digit, then A is 0 and we should stop

  or a

  ret z

#else

  ; the number of digits is not declared externally

  ; the first digit is written.

  ; if we only wanted 1 digit, then A is 0 and we should stop

#if FORMAT_LEN < 2

  ret

#else

  ld a,FORMAT_LEN

#endif

#endif

; we want D more digits (an extra one for rounding)

f32toa_digits_loop:

  push af

  call f32toa_next_digit

  pop af

f32toa_digits_start:

  dec a

  jr nz,f32toa_digits_loop

  ret

f32toa_next_digit:

; multiply 0.EBC by 10

  push bc

  ld b,h

  ld c,l

  ld a,e

  ld d,6  ;overflow digit. We shift d 3 times, that 6 turns into a 0x30 == '0'

  add hl,hl

  adc a,a

  rl d

  add hl,hl

  adc a,a

  rl d

  add hl,bc

  adc a,e

  jr nc,$+3

  inc d

  add hl,hl

  adc a,a

  ld e,a

  ld a,d

  adc a,a

  pop bc

  inc bc

  ld (bc),a

  ret

f32toa_adjust:

  ld hl,f32_pown10_LUT-4

  jr c,f32toa_pow10LUT_mul

  neg

  ld hl,f32_pow10_LUT-4

f32toa_pow10LUT_mul:

;HL points to the first entry of the LUT

;(f32toa_x) is the accumulator

;bottom 6 bits of A control which terms to multiply by

  ld de,f32toa_x

  ld b,d

  ld c,e

; process f32toa_pow10LUT_mul_sub 6 times

  call f32toa_pow10LUT_mul_sub3

f32toa_pow10LUT_mul_sub3:

  call f32toa_pow10LUT_mul_sub

  call f32toa_pow10LUT_mul_sub

f32toa_pow10LUT_mul_sub:

  inc hl

  inc hl

  inc hl

  inc hl

  rra

  jp c,f32mul

  ret

f32toa_return_0:

  ld (hl),'0'

  inc hl

  ld (hl),0

  ret

f32toa_return_infnan:

  rl b  ; save the sign

  ld a,e

  add a,a

  ld de,(f32toa_x)

  or d

  or e

  ex de,hl

  ld hl,str_NaN

  jr nz,f32toa_return

  ld hl,str_inf

  rr b

  jr nc,f32toa_return

  ld a,'-'

  ld (de),a

  inc de

f32toa_return:

  jp mov4

#include "formatstr.z80"

#endif