mirror of
https://github.com/charlienet/go-mixed.git
synced 2025-07-17 16:12:42 +08:00
79 lines
1.3 KiB
Go
79 lines
1.3 KiB
Go
package rand
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import (
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_ "unsafe"
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)
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var fastGenerator = &fastRandGenerator{}
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type fastRandGenerator struct {
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}
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func NewFastRandGenerator() *fastRandGenerator {
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return fastGenerator
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}
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func (*fastRandGenerator) Int63() int64 {
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uu := uint64(uint64(Fastrand())<<32) ^ uint64(Fastrand())
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return int64(uu << 1 >> 1)
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}
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func (r *fastRandGenerator) Int63n(n int64) int64 {
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if n <= 0 {
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panic("invalid argument to Int63n")
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}
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if n&(n-1) == 0 { // n is power of two, can mask
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return r.Int63() & (n - 1)
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}
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max := int64((1 << 63) - 1 - (1<<63)%uint64(n))
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v := r.Int63()
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for v > max {
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v = r.Int63()
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}
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return v % n
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}
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func (*fastRandGenerator) Int31() int32 {
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u := Fastrand()
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return int32(u << 1 >> 1)
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}
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func (r fastRandGenerator) Int31n(n int32) int32 {
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if n <= 0 {
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panic("invalid argument to Int31n")
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}
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if n&(n-1) == 0 { // n is power of two, can mask
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return r.Int31() & (n - 1)
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}
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max := int32((1 << 31) - 1 - (1<<31)%uint32(n))
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v := r.Int31()
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for v > max {
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v = r.Int31()
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}
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return v % n
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}
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func (*fastRandGenerator) Int() int {
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u := Fastrand()
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return int(u << 1 >> 1)
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}
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func (r *fastRandGenerator) Intn(n int) int {
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if n <= 0 {
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panic("invalid argument to Intn")
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}
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if n <= 1<<31-1 {
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return int(r.Int31n(int32(n)))
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}
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return int(r.Int63n(int64(n)))
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}
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//go:linkname Fastrand runtime.fastrand
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func Fastrand() uint32
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