Add vendoring

vendor/github.com/valyala/fastrand/fastrand.go

@@ -0,0 +1,79 @@
+// Package fastrand implements fast pesudorandom number generator
+// that should scale well on multi-CPU systems.
+//
+// Use crypto/rand instead of this package for generating
+// cryptographically secure random numbers.
+package fastrand
+
+import (
+	"sync"
+	"time"
+)
+
+// Uint32 returns pseudorandom uint32.
+//
+// It is safe calling this function from concurrent goroutines.
+func Uint32() uint32 {
+	v := rngPool.Get()
+	if v == nil {
+		v = &RNG{}
+	}
+	r := v.(*RNG)
+	x := r.Uint32()
+	rngPool.Put(r)
+	return x
+}
+
+var rngPool sync.Pool
+
+// Uint32n returns pseudorandom uint32 in the range [0..maxN).
+//
+// It is safe calling this function from concurrent goroutines.
+func Uint32n(maxN uint32) uint32 {
+	x := Uint32()
+	// See http://lemire.me/blog/2016/06/27/a-fast-alternative-to-the-modulo-reduction/
+	return uint32((uint64(x) * uint64(maxN)) >> 32)
+}
+
+// RNG is a pseudorandom number generator.
+//
+// It is unsafe to call RNG methods from concurrent goroutines.
+type RNG struct {
+	x uint32
+}
+
+// Uint32 returns pseudorandom uint32.
+//
+// It is unsafe to call this method from concurrent goroutines.
+func (r *RNG) Uint32() uint32 {
+	for r.x == 0 {
+		r.x = getRandomUint32()
+	}
+
+	// See https://en.wikipedia.org/wiki/Xorshift
+	x := r.x
+	x ^= x << 13
+	x ^= x >> 17
+	x ^= x << 5
+	r.x = x
+	return x
+}
+
+// Uint32n returns pseudorandom uint32 in the range [0..maxN).
+//
+// It is unsafe to call this method from concurrent goroutines.
+func (r *RNG) Uint32n(maxN uint32) uint32 {
+	x := r.Uint32()
+	// See http://lemire.me/blog/2016/06/27/a-fast-alternative-to-the-modulo-reduction/
+	return uint32((uint64(x) * uint64(maxN)) >> 32)
+}
+
+// Seed sets the r state to n.
+func (r *RNG) Seed(n uint32) {
+	r.x = n
+}
+
+func getRandomUint32() uint32 {
+	x := time.Now().UnixNano()
+	return uint32((x >> 32) ^ x)
+}