Update deps

vendor/golang.org/x/exp/rand/rng.go

@@ -0,0 +1,91 @@
+// Copyright 2017 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 rand
+
+import (
+	"encoding/binary"
+	"io"
+	"math/bits"
+)
+
+// PCGSource is an implementation of a 64-bit permuted congruential
+// generator as defined in
+//
+//	PCG: A Family of Simple Fast Space-Efficient Statistically Good
+//	Algorithms for Random Number Generation
+//	Melissa E. O’Neill, Harvey Mudd College
+//	http://www.pcg-random.org/pdf/toms-oneill-pcg-family-v1.02.pdf
+//
+// The generator here is the congruential generator PCG XSL RR 128/64 (LCG)
+// as found in the software available at http://www.pcg-random.org/.
+// It has period 2^128 with 128 bits of state, producing 64-bit values.
+// Is state is represented by two uint64 words.
+type PCGSource struct {
+	low  uint64
+	high uint64
+}
+
+const (
+	maxUint32 = (1 << 32) - 1
+
+	multiplier = 47026247687942121848144207491837523525
+	mulHigh    = multiplier >> 64
+	mulLow     = multiplier & maxUint64
+
+	increment = 117397592171526113268558934119004209487
+	incHigh   = increment >> 64
+	incLow    = increment & maxUint64
+
+	// TODO: Use these?
+	initializer = 245720598905631564143578724636268694099
+	initHigh    = initializer >> 64
+	initLow     = initializer & maxUint64
+)
+
+// Seed uses the provided seed value to initialize the generator to a deterministic state.
+func (pcg *PCGSource) Seed(seed uint64) {
+	pcg.low = seed
+	pcg.high = seed // TODO: What is right?
+}
+
+// Uint64 returns a pseudo-random 64-bit unsigned integer as a uint64.
+func (pcg *PCGSource) Uint64() uint64 {
+	pcg.multiply()
+	pcg.add()
+	// XOR high and low 64 bits together and rotate right by high 6 bits of state.
+	return bits.RotateLeft64(pcg.high^pcg.low, -int(pcg.high>>58))
+}
+
+func (pcg *PCGSource) add() {
+	var carry uint64
+	pcg.low, carry = bits.Add64(pcg.low, incLow, 0)
+	pcg.high, _ = bits.Add64(pcg.high, incHigh, carry)
+}
+
+func (pcg *PCGSource) multiply() {
+	hi, lo := bits.Mul64(pcg.low, mulLow)
+	hi += pcg.high * mulLow
+	hi += pcg.low * mulHigh
+	pcg.low = lo
+	pcg.high = hi
+}
+
+// MarshalBinary returns the binary representation of the current state of the generator.
+func (pcg *PCGSource) MarshalBinary() ([]byte, error) {
+	var buf [16]byte
+	binary.BigEndian.PutUint64(buf[:8], pcg.high)
+	binary.BigEndian.PutUint64(buf[8:], pcg.low)
+	return buf[:], nil
+}
+
+// UnmarshalBinary sets the state of the generator to the state represented in data.
+func (pcg *PCGSource) UnmarshalBinary(data []byte) error {
+	if len(data) < 16 {
+		return io.ErrUnexpectedEOF
+	}
+	pcg.low = binary.BigEndian.Uint64(data[8:])
+	pcg.high = binary.BigEndian.Uint64(data[:8])
+	return nil
+}