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/*
Package ftoa provides ECMAScript-compliant floating point number conversion to string.
It contains code ported from Rhino (https://github.com/mozilla/rhino/blob/master/src/org/mozilla/javascript/DToA.java)
as well as from the original code by David M. Gay.
See LICENSE_LUCENE for the original copyright message and disclaimer.
*/
package ftoa
import (
"math"
)
const (
frac_mask = 0xfffff
exp_shift = 20
exp_msk1 = 0x100000
exp_shiftL = 52
exp_mask_shifted = 0x7ff
frac_maskL = 0xfffffffffffff
exp_msk1L = 0x10000000000000
exp_shift1 = 20
exp_mask = 0x7ff00000
bias = 1023
p = 53
bndry_mask = 0xfffff
log2P = 1
)
func lo0bits(x uint32) (k int) {
if (x & 7) != 0 {
if (x & 1) != 0 {
return 0
}
if (x & 2) != 0 {
return 1
}
return 2
}
if (x & 0xffff) == 0 {
k = 16
x >>= 16
}
if (x & 0xff) == 0 {
k += 8
x >>= 8
}
if (x & 0xf) == 0 {
k += 4
x >>= 4
}
if (x & 0x3) == 0 {
k += 2
x >>= 2
}
if (x & 1) == 0 {
k++
x >>= 1
if (x & 1) == 0 {
return 32
}
}
return
}
func hi0bits(x uint32) (k int) {
if (x & 0xffff0000) == 0 {
k = 16
x <<= 16
}
if (x & 0xff000000) == 0 {
k += 8
x <<= 8
}
if (x & 0xf0000000) == 0 {
k += 4
x <<= 4
}
if (x & 0xc0000000) == 0 {
k += 2
x <<= 2
}
if (x & 0x80000000) == 0 {
k++
if (x & 0x40000000) == 0 {
return 32
}
}
return
}
func stuffBits(bits []byte, offset int, val uint32) {
bits[offset] = byte(val >> 24)
bits[offset+1] = byte(val >> 16)
bits[offset+2] = byte(val >> 8)
bits[offset+3] = byte(val)
}
func d2b(d float64, b []byte) (e, bits int, dblBits []byte) {
dBits := math.Float64bits(d)
d0 := uint32(dBits >> 32)
d1 := uint32(dBits)
z := d0 & frac_mask
d0 &= 0x7fffffff /* clear sign bit, which we ignore */
var de, k, i int
if de = int(d0 >> exp_shift); de != 0 {
z |= exp_msk1
}
y := d1
if y != 0 {
dblBits = b[:8]
k = lo0bits(y)
y >>= k
if k != 0 {
stuffBits(dblBits, 4, y|z<<(32-k))
z >>= k
} else {
stuffBits(dblBits, 4, y)
}
stuffBits(dblBits, 0, z)
if z != 0 {
i = 2
} else {
i = 1
}
} else {
dblBits = b[:4]
k = lo0bits(z)
z >>= k
stuffBits(dblBits, 0, z)
k += 32
i = 1
}
if de != 0 {
e = de - bias - (p - 1) + k
bits = p - k
} else {
e = de - bias - (p - 1) + 1 + k
bits = 32*i - hi0bits(z)
}
return
}
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