cryptobyte: add ReadUint64 and AddUint64

Fixes golang/go#53481. Change-Id: Ic00eef498d1d3b5b0ca5c9c526fac7c26de30cf2 Reviewed-on: https://go-review.googlesource.com/c/crypto/+/421014 TryBot-Result: Gopher Robot <gobot@golang.org> Auto-Submit: Filippo Valsorda <filippo@golang.org> Run-TryBot: hopehook <hopehook@qq.com> Reviewed-by: Damien Neil <dneil@google.com> Reviewed-by: Roland Shoemaker <roland@golang.org>

Author: hopehook

cryptobyte/builder.go

@@ -95,6 +95,11 @@ func (b *Builder) AddUint32(v uint32) {
 b.add(byte(v>>24), byte(v>>16), byte(v>>8), byte(v))
 }
 
+// AddUint64 appends a big-endian, 64-bit value to the byte string.
+func (b *Builder) AddUint64(v uint64) {
+b.add(byte(v>>56), byte(v>>48), byte(v>>40), byte(v>>32), byte(v>>24), byte(v>>16), byte(v>>8), byte(v))
+}
+
 // AddBytes appends a sequence of bytes to the byte string.
 func (b *Builder) AddBytes(v []byte) {
 b.add(v...)

cryptobyte/cryptobyte_test.go

@@ -141,7 +141,7 @@ func TestUint24(t *testing.T) {
 var s String = b.BytesOrPanic()
 var v uint32
 if !s.ReadUint24(&v) {
-t.Error("ReadUint8() = false, want true")
+t.Error("ReadUint24() = false, want true")
 }
 if v != 0xfffefd {
 t.Errorf("v = %d, want fffefd", v)
@@ -169,7 +169,7 @@ func TestUint32(t *testing.T) {
 var s String = b.BytesOrPanic()
 var v uint32
 if !s.ReadUint32(&v) {
-t.Error("ReadUint8() = false, want true")
+t.Error("ReadUint32() = false, want true")
 }
 if v != 0xfffefdfc {
 t.Errorf("v = %x, want fffefdfc", v)
@@ -179,6 +179,26 @@ func TestUint32(t *testing.T) {
 }
 }
 
+func TestUint64(t *testing.T) {
+var b Builder
+b.AddUint64(0xf2fefefcff3cfdfc)
+if err := builderBytesEq(&b, 242, 254, 254, 252, 255, 60, 253, 252); err != nil {
+t.Error(err)
+}
+
+var s String = b.BytesOrPanic()
+var v uint64
+if !s.ReadUint64(&v) {
+t.Error("ReadUint64() = false, want true")
+}
+if v != 0xf2fefefcff3cfdfc {
+t.Errorf("v = %x, want f2fefefcff3cfdfc", v)
+}
+if len(s) != 0 {
+t.Errorf("len(s) = %d, want 0", len(s))
+}
+}
+
 func TestUMultiple(t *testing.T) {
 var b Builder
 b.AddUint8(23)

cryptobyte/string.go

@@ -81,6 +81,17 @@ func (s *String) ReadUint32(out *uint32) bool {
 return true
 }
 
+// ReadUint64 decodes a big-endian, 64-bit value into out and advances over it.
+// It reports whether the read was successful.
+func (s *String) ReadUint64(out *uint64) bool {
+v := s.read(8)
+if v == nil {
+return false
+}
+*out = uint64(v[0])<<56 | uint64(v[1])<<48 | uint64(v[2])<<40 | uint64(v[3])<<32 | uint64(v[4])<<24 | uint64(v[5])<<16 | uint64(v[6])<<8 | uint64(v[7])
+return true
+}
+
 func (s *String) readUnsigned(out *uint32, length int) bool {
 v := s.read(length)
 if v == nil {