ref: ba1476058afaffc3f24ca8fbde11234def04d1bf
dir: /lib/std/fltfmt.myr/
use "alloc"
use "bigint"
use "die"
use "extremum"
use "fltbits"
use "intfmt"
use "option"
use "slpush"
use "strbuf"
use "types"
use "utf"
use "memops"
pkg std =
pkglocal const MNormal = 0
pkglocal const MAbsolute = 1
pkglocal const MRelative = 2
pkglocal type fltparams = struct
mode : int
cutoff : size
scientific : bool
padto : size
padfill : char
;;
pkglocal const flt64bfmt : (sb : strbuf#, opts : fltparams, val : flt64 -> void)
pkglocal const flt32bfmt : (sb : strbuf#, opts : fltparams, val : flt32 -> void)
;;
const Dblbias = 1023
const Fltbias = 127
const flt64bfmt = {sb, opts, val
var isneg, exp, mant
if isnan(val)
-> nanfmt(sb, opts)
;;
(isneg, exp, mant) = flt64explode(val)
if exp > Dblbias
-> inffmt(sb, opts, isneg)
;;
var valsb = mksb()
exp = max(exp, 1 - Dblbias)
dragon4(valsb, false, mant, exp - 52, Dblbias, opts.mode, -opts.cutoff, opts.scientific)
-> blobfmt(sb, sbfin(valsb), opts, isneg)
}
const flt32bfmt = {sb, opts, val
var isneg, exp, mant
if isnan(val)
-> nanfmt(sb, opts)
;;
(isneg, exp, mant) = flt32explode(val)
if (exp : int64) > Fltbias
-> inffmt(sb, opts, isneg)
;;
var valsb = mksb()
exp = (max((exp : int64), 1 - Fltbias) : int32)
dragon4(valsb, false, (mant : uint64), (exp - 23 : int64), Fltbias, opts.mode, -opts.cutoff, opts.scientific)
-> blobfmt(sb, sbfin(valsb), opts, isneg)
}
const nanfmt = {sb, opts
var npad = clamp(opts.padto - 3, 0, opts.padto)
for var j = 0; j < npad; j++
sbputc(sb, opts.padfill)
;;
sbputs(sb, "NaN")
}
const inffmt = {sb, opts, isneg
var s = "Inf"
var l = 3
if isneg
s = "-Inf"
l = 4
;;
var npad = clamp(opts.padto - l, 0, opts.padto)
for var j = 0; j < npad; j++
sbputc(sb, opts.padfill)
;;
sbputs(sb, s)
}
const blobfmt = {sb, blob, opts, isneg
/* No exotic characters, so no need for strcellwidth */
var width = blob.len
if isneg
width++
;;
var npad = clamp(opts.padto - width, 0, opts.padto)
if opts.padfill == '0' && isneg
sbputb(sb, ('-' : byte))
;;
for var j = 0; j < npad; j++
sbputc(sb, opts.padfill)
;;
if opts.padfill != '0' && isneg
sbputb(sb, ('-' : byte))
;;
sbputs(sb, blob)
}
/*
sb: output buffer
e: exponent
p: precision
f: mantissa
floating value: x = f^(e - p)
*/
const dragon4 = {sb, isneg, f, e, p, mode, cutoff, scientific
var r, s, t, u, v, y
var udig
var mm, mp /* margins above and below */
var roundup
var low, high
var k
var tenpower : int64 = 0
var a, i
if isneg
sbputs(sb, "-")
;;
/* if we have zero for the mantissa, we can return early */
if f == 0
sbputs(sb, "0.0")
if scientific
sbputs(sb, "e0")
;;
-> void
;;
/* initialize */
roundup = false
low = false
high = false
u = mkbigint(0)
r = bigshli(mkbigint(f), max(e, 0))
s = bigshli(mkbigint(1), max(0, -e))
mm = bigshli(mkbigint(1), max(e, 0))
mp = bigdup(mm)
/* fixup: unequal gaps */
t = mkbigint(1)
bigshli(t, p - 1)
if bigeqi(t, f)
bigshli(mp, 1)
bigshli(r, 1)
bigshli(s, 1)
;;
bigfree(t)
k = 0
while true
/* r < ceil(s/b) */
t = bigdup(s)
bigaddi(t, 9)
bigdivi(t, 10)
match bigcmp(r, t)
| `Before:
k--
bigmuli(r, 10)
bigmuli(mm, 10)
bigmuli(mp, 10)
| _:
bigfree(t)
break
;;
bigfree(t)
;;
while true
t = bigdup(r)
bigshli(t, 1)
bigadd(t, mp)
while true
u = bigdup(s)
bigshli(u, 1)
match bigcmp(t, u)
| `Before:
bigfree(u)
break
| _:
k++
bigmuli(s, 10)
bigfree(u)
;;
;;
if mode == MNormal
cutoff = k
else
if mode == MRelative
if cutoff >= 0
cutoff = -1
;;
cutoff += k
;;
a = cutoff - k
/* common between relative and absolute */
y = bigdup(s)
if a > 0
for i = 0; i < a; i++
bigmuli(y, 10)
;;
else
for i = 0; i < -a; i++
bigaddi(y, 9)
bigdivi(y, 10)
;;
;;
match bigcmp(y, mm)
| `Before: /* nothing */
| _:
bigfree(mm)
mm = bigdup(y)
;;
match bigcmp(y, mp)
| `Before: /* nothing */
| _:
bigfree(mp)
mp = bigdup(y)
roundup = true
/* recalculate 2*R + M+ for the loop termination */
bigfree(t)
t = bigdup(r)
bigshli(t, 1)
bigadd(t, mp)
;;
bigfree(y)
;;
u = bigdup(s)
bigshli(u, 1)
match bigcmp(t, u)
| `Before:
bigfree(t)
bigfree(u)
break
| _:
;;
;;
if scientific
tenpower = (k - 1 : int64)
cutoff += (1 - k)
k = 1
;;
if k <= 0
sbputs(sb, "0.")
for var i = 0; i < -k; i++
sbputs(sb, "0")
;;
;;
while true
k--
bigmuli(r, 10)
u = bigdup(r);
bigdiv(u, s)
bigmod(r, s)
bigmuli(mm, 10)
bigmuli(mp, 10)
low = false
t = bigdup(r)
bigshli(t, 1)
match bigcmp(t, mm)
| `Before: low = true
| _:
;;
bigfree(t)
/* v = 2*r */
v = bigdup(r)
bigshli(v, 1)
/* t = 2*s - mp */
t = bigdup(s)
bigshli(t, 1)
bigsub(t, mp)
match bigcmp(v, t)
| `Before: high = false;
| `Equal: high = roundup;
| `After: high = true;
;;
bigfree(v)
bigfree(t)
if low || high || k == cutoff
break
;;
format(sb, lowdig(u), k)
bigfree(u)
;;
/* format the last digit */
udig = lowdig(u)
if low && !high
format(sb, udig, k)
elif high && !low
format(sb, udig + 1, k)
else
bigmuli(r, 2)
match bigcmp(r, s)
| `Before: format(sb, udig, k)
| `Equal: format(sb, udig, k)
| `After: format(sb, udig + 1, k)
;;
;;
k--
if !scientific && cutoff > -1
cutoff = -1
;;
while k >= cutoff
format(sb, 0, k--)
;;
if scientific
sbputs(sb, "e")
intfmt(sb, [ .base = 10 ], true, (tenpower : uint64), 64)
;;
bigfree(u)
bigfree(r)
bigfree(s)
bigfree(mm)
bigfree(mp)
}
const lowdig = {u
if u.dig.len > 0
-> u.dig[0]
;;
-> 0
}
const format = {sb, d, k
const dig = "0123456789"
sbputb(sb, dig[d])
if k == 0
sbputs(sb, ".")
;;
}