Add more context

common/random/rng.go

@@ -2,6 +2,7 @@ package random
 
 import (
 	"crypto/rand"
+	"encoding/binary"
 	"io"
 
 	"github.com/sagernet/sing/common"
@@ -10,9 +11,37 @@ import (
 
 var System = rand.Reader
 
-func Blake3KeyedHash() io.Reader {
+func Blake3KeyedHash() Source {
 	key := make([]byte, 32)
 	common.Must1(io.ReadFull(System, key))
 	h := blake3.New(1024, key)
-	return h.XOF()
+	return Source{h.XOF()}
+}
+
+const (
+	rngMax  = 1 << 63
+	rngMask = rngMax - 1
+)
+
+type Source struct {
+	io.Reader
+}
+
+func (s Source) Int63() int64 {
+	return s.Int64() & rngMask
+}
+
+func (s Source) Int64() int64 {
+	var num int64
+	common.Must(binary.Read(s, binary.BigEndian, &num))
+	return num
+}
+
+func (s Source) Uint64() uint64 {
+	var num uint64
+	common.Must(binary.Read(s, binary.BigEndian, &num))
+	return num
+}
+
+func (s Source) Seed(int64) {
 }