golang bits 代码
文件路径：/src/math/bits.go
/ Copyright 2009 The Go Authors. All rights reserved.
/ Use of this source code is governed by a BSD-style
/ license that can be found in the LICENSE file.
package math
const (
uvnan = 0x7FF8000000000001
uvinf = 0x7FF0000000000000
uvneginf = 0xFFF0000000000000
uvone = 0x3FF0000000000000
mask = 0x7FF
shift = 64 - 11 - 1
bias = 1023
signMask = 1 << 63
fracMask = 1<<shift - 1
)
/ Inf returns positive infinity if sign >= 0, negative infinity if sign < 0.
func Inf(sign int) float64 {
var v uint64
if sign >= 0 {
v = uvinf
} else {
v = uvneginf
}
return Float64frombits(v)
}
/ NaN returns an IEEE 754 “not-a-number” value.
func NaN() float64 { return Float64frombits(uvnan) }
/ IsNaN reports whether f is an IEEE 754 “not-a-number” value.
func IsNaN(f float64) (is bool) {
/ IEEE 754 says that only NaNs satisfy f != f.
/ To avoid the floating-point hardware, could use:
/ x := Float64bits(f);
/ return uint32(x>>shift)&mask == mask && x != uvinf && x != uvneginf
return f != f
}
/ IsInf reports whether f is an infinity, according to sign.
/ If sign > 0, IsInf reports whether f is positive infinity.
/ If sign < 0, IsInf reports whether f is negative infinity.
/ If sign == 0, IsInf reports whether f is either infinity.
func IsInf(f float64, sign int) bool {
/ Test for infinity by comparing against maximum float.
/ To avoid the floating-point hardware, could use:
/ x := Float64bits(f);
/ return sign >= 0 && x == uvinf || sign <= 0 && x == uvneginf;
return sign >= 0 && f > MaxFloat64 || sign <= 0 && f < -MaxFloat64
}
/ normalize returns a normal number y and exponent exp
/ satisfying x == y × 2**exp. It assumes x is finite and non-zero.
func normalize(x float64) (y float64, exp int) {
const SmallestNormal = 2.2250738585072014e-308 / 2**-1022
if Abs(x) < SmallestNormal {
return x * (1 << 52), -52
}
return x, 0
}