dns/dnsmessage: use map[string]uint16 instead of map[string]int

The compression pointer is limited to 14 bits, so there is no
need to use int, uint16 is fine.

Change-Id: I2276cbf63761e26a7e8590f0337930db87895ea5
GitHub-Last-Rev: e04b451
GitHub-Pull-Request: #192
Reviewed-on: https://go-review.googlesource.com/c/net/+/528955
Reviewed-by: Matthew Dempsky <[email protected]>
Run-TryBot: Mateusz Poliwczak <[email protected]>
Reviewed-by: Ian Lance Taylor <[email protected]>
Auto-Submit: Ian Lance Taylor <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: mateusz834

dns/dnsmessage/message.go

@@ -492,7 +492,7 @@ func (r *Resource) GoString() string {
 // A ResourceBody is a DNS resource record minus the header.
 type ResourceBody interface {
 	// pack packs a Resource except for its header.
-	pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error)
+	pack(msg []byte, compression map[string]uint16, compressionOff int) ([]byte, error)
 
 	// realType returns the actual type of the Resource. This is used to
 	// fill in the header Type field.
@@ -503,7 +503,7 @@ type ResourceBody interface {
 }
 
 // pack appends the wire format of the Resource to msg.
-func (r *Resource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) {
+func (r *Resource) pack(msg []byte, compression map[string]uint16, compressionOff int) ([]byte, error) {
 	if r.Body == nil {
 		return msg, errNilResouceBody
 	}
@@ -1129,7 +1129,7 @@ func (m *Message) AppendPack(b []byte) ([]byte, error) {
 	// DNS messages can be a maximum of 512 bytes long. Without compression,
 	// many DNS response messages are over this limit, so enabling
 	// compression will help ensure compliance.
-	compression := map[string]int{}
+	compression := map[string]uint16{}
 
 	for i := range m.Questions {
 		var err error
@@ -1220,7 +1220,7 @@ type Builder struct {
 
 	// compression is a mapping from name suffixes to their starting index
 	// in msg.
-	compression map[string]int
+	compression map[string]uint16
 }
 
 // NewBuilder creates a new builder with compression disabled.
@@ -1257,7 +1257,7 @@ func NewBuilder(buf []byte, h Header) Builder {
 //
 // Compression should be enabled before any sections are added for best results.
 func (b *Builder) EnableCompression() {
-	b.compression = map[string]int{}
+	b.compression = map[string]uint16{}
 }
 
 func (b *Builder) startCheck(s section) error {
@@ -1673,7 +1673,7 @@ func (h *ResourceHeader) GoString() string {
 // pack appends the wire format of the ResourceHeader to oldMsg.
 //
 // lenOff is the offset in msg where the Length field was packed.
-func (h *ResourceHeader) pack(oldMsg []byte, compression map[string]int, compressionOff int) (msg []byte, lenOff int, err error) {
+func (h *ResourceHeader) pack(oldMsg []byte, compression map[string]uint16, compressionOff int) (msg []byte, lenOff int, err error) {
 	msg = oldMsg
 	if msg, err = h.Name.pack(msg, compression, compressionOff); err != nil {
 		return oldMsg, 0, &nestedError{"Name", err}
@@ -1946,7 +1946,7 @@ func (n *Name) GoString() string {
 //
 // The compression map will be updated with new domain suffixes. If compression
 // is nil, compression will not be used.
-func (n *Name) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) {
+func (n *Name) pack(msg []byte, compression map[string]uint16, compressionOff int) ([]byte, error) {
 	oldMsg := msg
 
 	if n.Length > nonEncodedNameMax {
@@ -2010,7 +2010,7 @@ func (n *Name) pack(msg []byte, compression map[string]int, compressionOff int)
 					// multiple times (for next labels).
 					nameAsStr = string(n.Data[:n.Length])
 				}
-				compression[nameAsStr[i:]] = newPtr
+				compression[nameAsStr[i:]] = uint16(newPtr)
 			}
 		}
 	}
@@ -2150,7 +2150,7 @@ type Question struct {
 }
 
 // pack appends the wire format of the Question to msg.
-func (q *Question) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) {
+func (q *Question) pack(msg []byte, compression map[string]uint16, compressionOff int) ([]byte, error) {
 	msg, err := q.Name.pack(msg, compression, compressionOff)
 	if err != nil {
 		return msg, &nestedError{"Name", err}
@@ -2246,7 +2246,7 @@ func (r *CNAMEResource) realType() Type {
 }
 
 // pack appends the wire format of the CNAMEResource to msg.
-func (r *CNAMEResource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) {
+func (r *CNAMEResource) pack(msg []byte, compression map[string]uint16, compressionOff int) ([]byte, error) {
 	return r.CNAME.pack(msg, compression, compressionOff)
 }
 
@@ -2274,7 +2274,7 @@ func (r *MXResource) realType() Type {
 }
 
 // pack appends the wire format of the MXResource to msg.
-func (r *MXResource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) {
+func (r *MXResource) pack(msg []byte, compression map[string]uint16, compressionOff int) ([]byte, error) {
 	oldMsg := msg
 	msg = packUint16(msg, r.Pref)
 	msg, err := r.MX.pack(msg, compression, compressionOff)
@@ -2313,7 +2313,7 @@ func (r *NSResource) realType() Type {
 }
 
 // pack appends the wire format of the NSResource to msg.
-func (r *NSResource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) {
+func (r *NSResource) pack(msg []byte, compression map[string]uint16, compressionOff int) ([]byte, error) {
 	return r.NS.pack(msg, compression, compressionOff)
 }
 
@@ -2340,7 +2340,7 @@ func (r *PTRResource) realType() Type {
 }
 
 // pack appends the wire format of the PTRResource to msg.
-func (r *PTRResource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) {
+func (r *PTRResource) pack(msg []byte, compression map[string]uint16, compressionOff int) ([]byte, error) {
 	return r.PTR.pack(msg, compression, compressionOff)
 }
 
@@ -2377,7 +2377,7 @@ func (r *SOAResource) realType() Type {
 }
 
 // pack appends the wire format of the SOAResource to msg.
-func (r *SOAResource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) {
+func (r *SOAResource) pack(msg []byte, compression map[string]uint16, compressionOff int) ([]byte, error) {
 	oldMsg := msg
 	msg, err := r.NS.pack(msg, compression, compressionOff)
 	if err != nil {
@@ -2449,7 +2449,7 @@ func (r *TXTResource) realType() Type {
 }
 
 // pack appends the wire format of the TXTResource to msg.
-func (r *TXTResource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) {
+func (r *TXTResource) pack(msg []byte, compression map[string]uint16, compressionOff int) ([]byte, error) {
 	oldMsg := msg
 	for _, s := range r.TXT {
 		var err error
@@ -2505,7 +2505,7 @@ func (r *SRVResource) realType() Type {
 }
 
 // pack appends the wire format of the SRVResource to msg.
-func (r *SRVResource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) {
+func (r *SRVResource) pack(msg []byte, compression map[string]uint16, compressionOff int) ([]byte, error) {
 	oldMsg := msg
 	msg = packUint16(msg, r.Priority)
 	msg = packUint16(msg, r.Weight)
@@ -2556,7 +2556,7 @@ func (r *AResource) realType() Type {
 }
 
 // pack appends the wire format of the AResource to msg.
-func (r *AResource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) {
+func (r *AResource) pack(msg []byte, compression map[string]uint16, compressionOff int) ([]byte, error) {
 	return packBytes(msg, r.A[:]), nil
 }
 
@@ -2590,7 +2590,7 @@ func (r *AAAAResource) GoString() string {
 }
 
 // pack appends the wire format of the AAAAResource to msg.
-func (r *AAAAResource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) {
+func (r *AAAAResource) pack(msg []byte, compression map[string]uint16, compressionOff int) ([]byte, error) {
 	return packBytes(msg, r.AAAA[:]), nil
 }
 
@@ -2630,7 +2630,7 @@ func (r *OPTResource) realType() Type {
 	return TypeOPT
 }
 
-func (r *OPTResource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) {
+func (r *OPTResource) pack(msg []byte, compression map[string]uint16, compressionOff int) ([]byte, error) {
 	for _, opt := range r.Options {
 		msg = packUint16(msg, opt.Code)
 		l := uint16(len(opt.Data))
@@ -2688,7 +2688,7 @@ func (r *UnknownResource) realType() Type {
 }
 
 // pack appends the wire format of the UnknownResource to msg.
-func (r *UnknownResource) pack(msg []byte, compression map[string]int, compressionOff int) ([]byte, error) {
+func (r *UnknownResource) pack(msg []byte, compression map[string]uint16, compressionOff int) ([]byte, error) {
 	return packBytes(msg, r.Data[:]), nil
 }
 

dns/dnsmessage/message_test.go

@@ -164,7 +164,7 @@ func TestQuestionPackUnpack(t *testing.T) {
 		Type:  TypeA,
 		Class: ClassINET,
 	}
-	buf, err := want.pack(make([]byte, 1, 50), map[string]int{}, 1)
+	buf, err := want.pack(make([]byte, 1, 50), map[string]uint16{}, 1)
 	if err != nil {
 		t.Fatal("Question.pack() =", err)
 	}
@@ -243,7 +243,7 @@ func TestNamePackUnpack(t *testing.T) {
 
 	for _, test := range tests {
 		in := MustNewName(test.in)
-		buf, err := in.pack(make([]byte, 0, 30), map[string]int{}, 0)
+		buf, err := in.pack(make([]byte, 0, 30), map[string]uint16{}, 0)
 		if err != test.err {
 			t.Errorf("got %q.pack() = %v, want = %v", test.in, err, test.err)
 			continue
@@ -305,7 +305,7 @@ func TestNameUnpackTooLongName(t *testing.T) {
 
 func TestIncompressibleName(t *testing.T) {
 	name := MustNewName("example.com.")
-	compression := map[string]int{}
+	compression := map[string]uint16{}
 	buf, err := name.pack(make([]byte, 0, 100), compression, 0)
 	if err != nil {
 		t.Fatal("first Name.pack() =", err)
@@ -623,7 +623,7 @@ func TestVeryLongTxt(t *testing.T) {
 			strings.Repeat(".", 255),
 		}},
 	}
-	buf, err := want.pack(make([]byte, 0, 8000), map[string]int{}, 0)
+	buf, err := want.pack(make([]byte, 0, 8000), map[string]uint16{}, 0)
 	if err != nil {
 		t.Fatal("Resource.pack() =", err)
 	}
@@ -647,7 +647,7 @@ func TestVeryLongTxt(t *testing.T) {
 
 func TestTooLongTxt(t *testing.T) {
 	rb := TXTResource{[]string{strings.Repeat(".", 256)}}
-	if _, err := rb.pack(make([]byte, 0, 8000), map[string]int{}, 0); err != errStringTooLong {
+	if _, err := rb.pack(make([]byte, 0, 8000), map[string]uint16{}, 0); err != errStringTooLong {
 		t.Errorf("packing TXTResource with 256 character string: got err = %v, want = %v", err, errStringTooLong)
 	}
 }