feat: Leverage the new math/rand/v2 ChaCha8 CSPRNG

uuid.go

@@ -6,11 +6,15 @@ package uuid
 
 import (
 	"bytes"
-	"crypto/rand"
 	"encoding/hex"
 	"errors"
 	"fmt"
 	"io"
+
+	// Uses math/rand/v2 for random number generation
+	// because it uses chacha8 as the default source,
+	// which is cryptographically secure and much faster
+
 	"strings"
 	"sync"
 )
@@ -42,8 +46,8 @@ const Standard = RFC4122
 const randPoolSize = 16 * 16
 
 var (
-	rander      = rand.Reader // random function
-	poolEnabled = false
+	rander      io.Reader = defaultRandReader{}
+	poolEnabled           = false
 	poolMu      sync.Mutex
 	poolPos     = randPoolSize     // protected with poolMu
 	pool        [randPoolSize]byte // protected with poolMu
@@ -52,7 +56,7 @@ var (
 	ErrInvalidBracketedFormat = errors.New("invalid bracketed UUID format")
 )
 
-type URNPrefixError struct { prefix string }
+type URNPrefixError struct{ prefix string }
 
 func (e URNPrefixError) Error() string {
 	return fmt.Sprintf("invalid urn prefix: %q", e.prefix)
@@ -215,10 +219,12 @@ func Must(uuid UUID, err error) UUID {
 }
 
 // Validate returns an error if s is not a properly formatted UUID in one of the following formats:
-//   xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
-//   urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
-//   xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
-//   {xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
+//
+//	xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+//	urn:uuid:xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
+//	xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+//	{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}
+//
 // It returns an error if the format is invalid, otherwise nil.
 func Validate(s string) error {
 	switch len(s) {
@@ -346,7 +352,7 @@ func (v Variant) String() string {
 // generator.
 func SetRand(r io.Reader) {
 	if r == nil {
-		rander = rand.Reader
+		rander = defaultRandReader{}
 		return
 	}
 	rander = r

version4.go

@@ -4,20 +4,24 @@
 
 package uuid
 
-import "io"
+import (
+	"encoding/binary"
+	"io"
+	chacha8RandV2 "math/rand/v2"
+)
 
 // New creates a new random UUID or panics.  New is equivalent to
 // the expression
 //
-//    uuid.Must(uuid.NewRandom())
+//	uuid.Must(uuid.NewRandom())
 func New() UUID {
 	return Must(NewRandom())
 }
 
 // NewString creates a new random UUID and returns it as a string or panics.
 // NewString is equivalent to the expression
 //
-//    uuid.New().String()
+//	uuid.New().String()
 func NewString() string {
 	return Must(NewRandom()).String()
 }
@@ -31,12 +35,16 @@ func NewString() string {
 //
 // A note about uniqueness derived from the UUID Wikipedia entry:
 //
-//  Randomly generated UUIDs have 122 random bits.  One's annual risk of being
-//  hit by a meteorite is estimated to be one chance in 17 billion, that
-//  means the probability is about 0.00000000006 (6 × 10−11),
-//  equivalent to the odds of creating a few tens of trillions of UUIDs in a
-//  year and having one duplicate.
+//	Randomly generated UUIDs have 122 random bits.  One's annual risk of being
+//	hit by a meteorite is estimated to be one chance in 17 billion, that
+//	means the probability is about 0.00000000006 (6 × 10−11),
+//	equivalent to the odds of creating a few tens of trillions of UUIDs in a
+//	year and having one duplicate.
 func NewRandom() (UUID, error) {
+	if _, ok := rander.(defaultRandReader); ok {
+		return fastRandV4DefaultZeroAlloc(), nil
+	}
+
 	if !poolEnabled {
 		return NewRandomFromReader(rander)
 	}
@@ -74,3 +82,36 @@ func newRandomFromPool() (UUID, error) {
 	uuid[8] = (uuid[8] & 0x3f) | 0x80 // Variant is 10
 	return uuid, nil
 }
+
+// Singleton with no state that implements
+// io.Reader and uses the default rand/v2
+// package to read bytes.
+type defaultRandReader struct{}
+
+// Read fills the provided byte slice `b` with random data using a
+// cryptographically secure random number generator.
+func (d defaultRandReader) Read(b []byte) (n int, err error) {
+	var num uint64
+	numByteIndex := 0
+
+	for i := range b {
+		if numByteIndex == 0 {
+			num = chacha8RandV2.Uint64()
+		}
+		b[i] = byte(num >> (numByteIndex * 8))
+		numByteIndex = (numByteIndex + 1) % 8
+	}
+
+	return len(b), nil
+}
+
+func fastRandV4DefaultZeroAlloc() UUID {
+	var uuid UUID
+	hi, low := chacha8RandV2.Uint64(), chacha8RandV2.Uint64()
+	binary.BigEndian.PutUint64(uuid[0:8], hi)
+	binary.BigEndian.PutUint64(uuid[8:16], low)
+
+	uuid[6] = (uuid[6] & 0x0f) | 0x40 // Version 4
+	uuid[8] = (uuid[8] & 0x3f) | 0x80 // Variant is 10
+	return uuid
+}