improve code quality (miekg#1228)

* Combine multiple `append`s into a single call

* Fix Yoda conditions

* Fix check for empty string

* revert "combine multiple `append`s"

Author: withshubh

defaults.go

@@ -349,10 +349,7 @@ func ReverseAddr(addr string) (arpa string, err error) {
 	// Add it, in reverse, to the buffer
 	for i := len(ip) - 1; i >= 0; i-- {
 		v := ip[i]
-		buf = append(buf, hexDigit[v&0xF])
-		buf = append(buf, '.')
-		buf = append(buf, hexDigit[v>>4])
-		buf = append(buf, '.')
+		buf = append(buf, hexDigit[v&0xF], '.', hexDigit[v>>4], '.')
 	}
 	// Append "ip6.arpa." and return (buf already has the final .)
 	buf = append(buf, "ip6.arpa."...)

dnssec_test.go

@@ -325,7 +325,7 @@ Activate: 20110302104537`
 	}
 	switch priv := p.(type) {
 	case *rsa.PrivateKey:
-		if 65537 != priv.PublicKey.E {
+		if priv.PublicKey.E != 65537 {
 			t.Error("exponenent should be 65537")
 		}
 	default:

dnsutil/util.go

@@ -30,10 +30,10 @@ func AddOrigin(s, origin string) string {
 	if dns.IsFqdn(s) {
 		return s // s is already a FQDN, no need to mess with it.
 	}
-	if len(origin) == 0 {
+	if origin == "" {
 		return s // Nothing to append.
 	}
-	if s == "@" || len(s) == 0 {
+	if s == "@" || s == "" {
 		return origin // Expand apex.
 	}
 	if origin == "." {
@@ -50,7 +50,7 @@ func TrimDomainName(s, origin string) string {
 	// If the return value ends in a ".", the domain was not the suffix.
 	// origin can end in "." or not. Either way the results should be the same.
 
-	if len(s) == 0 {
+	if s == "" {
 		return "@"
 	}
 	// Someone is using TrimDomainName(s, ".") to remove a dot if it exists.

labels.go

@@ -10,7 +10,7 @@ package dns
 // escaped dots (\.) for instance.
 // s must be a syntactically valid domain name, see IsDomainName.
 func SplitDomainName(s string) (labels []string) {
-	if len(s) == 0 {
+	if s == "" {
 		return nil
 	}
 	fqdnEnd := 0 // offset of the final '.' or the length of the name

parse_test.go

@@ -245,8 +245,7 @@ func testTXTRRQuick(t *testing.T) {
 		rrbytes := make([]byte, 0, len(owner)+2+2+4+2+len(rdata))
 		rrbytes = append(rrbytes, owner...)
 		rrbytes = append(rrbytes, typeAndClass...)
-		rrbytes = append(rrbytes, byte(len(rdata)>>8))
-		rrbytes = append(rrbytes, byte(len(rdata)))
+		rrbytes = append(rrbytes, byte(len(rdata)>>8), byte(len(rdata)))
 		rrbytes = append(rrbytes, rdata...)
 		rr, _, err := UnpackRR(rrbytes, 0)
 		if err != nil {

scan.go

@@ -1233,7 +1233,7 @@ func stringToCm(token string) (e, m uint8, ok bool) {
 			// 'nn.1' must be treated as 'nn-meters and 10cm, not 1cm.
 			cmeters *= 10
 		}
-		if len(s[0]) == 0 {
+		if s[0] == "" {
 			// This will allow omitting the 'meter' part, like .01 (meaning 0.01m = 1cm).
 			break
 		}

scan_rr.go

@@ -662,7 +662,7 @@ East:
 Altitude:
 	c.Next() // zBlank
 	l, _ = c.Next()
-	if len(l.token) == 0 || l.err {
+	if l.token == "" || l.err {
 		return &ParseError{"", "bad LOC Altitude", l}
 	}
 	if l.token[len(l.token)-1] == 'M' || l.token[len(l.token)-1] == 'm' {
@@ -722,15 +722,15 @@ func (rr *HIP) parse(c *zlexer, o string) *ParseError {
 
 	c.Next()        // zBlank
 	l, _ = c.Next() // zString
-	if len(l.token) == 0 || l.err {
+	if l.token == "" || l.err {
 		return &ParseError{"", "bad HIP Hit", l}
 	}
 	rr.Hit = l.token // This can not contain spaces, see RFC 5205 Section 6.
 	rr.HitLength = uint8(len(rr.Hit)) / 2
 
 	c.Next()        // zBlank
 	l, _ = c.Next() // zString
-	if len(l.token) == 0 || l.err {
+	if l.token == "" || l.err {
 		return &ParseError{"", "bad HIP PublicKey", l}
 	}
 	rr.PublicKey = l.token // This cannot contain spaces
@@ -997,7 +997,7 @@ func (rr *NSEC3) parse(c *zlexer, o string) *ParseError {
 	rr.Iterations = uint16(i)
 	c.Next()
 	l, _ = c.Next()
-	if len(l.token) == 0 || l.err {
+	if l.token == "" || l.err {
 		return &ParseError{"", "bad NSEC3 Salt", l}
 	}
 	if l.token != "-" {
@@ -1007,7 +1007,7 @@ func (rr *NSEC3) parse(c *zlexer, o string) *ParseError {
 
 	c.Next()
 	l, _ = c.Next()
-	if len(l.token) == 0 || l.err {
+	if l.token == "" || l.err {
 		return &ParseError{"", "bad NSEC3 NextDomain", l}
 	}
 	rr.HashLength = 20 // Fix for NSEC3 (sha1 160 bits)

sig0.go

@@ -17,7 +17,7 @@ func (rr *SIG) Sign(k crypto.Signer, m *Msg) ([]byte, error) {
 	if k == nil {
 		return nil, ErrPrivKey
 	}
-	if rr.KeyTag == 0 || len(rr.SignerName) == 0 || rr.Algorithm == 0 {
+	if rr.KeyTag == 0 || rr.SignerName == "" || rr.Algorithm == 0 {
 		return nil, ErrKey
 	}
 
@@ -78,7 +78,7 @@ func (rr *SIG) Verify(k *KEY, buf []byte) error {
 	if k == nil {
 		return ErrKey
 	}
-	if rr.KeyTag == 0 || len(rr.SignerName) == 0 || rr.Algorithm == 0 {
+	if rr.KeyTag == 0 || rr.SignerName == "" || rr.Algorithm == 0 {
 		return ErrKey
 	}
 

svcb.go

@@ -321,7 +321,7 @@ func (s *SVCBAlpn) pack() ([]byte, error) {
 	// Liberally estimate the size of an alpn as 10 octets
 	b := make([]byte, 0, 10*len(s.Alpn))
 	for _, e := range s.Alpn {
-		if len(e) == 0 {
+		if e == "" {
 			return nil, errors.New("dns: svcbalpn: empty alpn-id")
 		}
 		if len(e) > 255 {
@@ -390,7 +390,7 @@ func (*SVCBNoDefaultAlpn) unpack(b []byte) error {
 }
 
 func (*SVCBNoDefaultAlpn) parse(b string) error {
-	if len(b) != 0 {
+	if b != "" {
 		return errors.New("dns: svcbnodefaultalpn: no_default_alpn must have no value")
 	}
 	return nil

types.go

@@ -1472,7 +1472,7 @@ func StringToTime(s string) (uint32, error) {
 
 // saltToString converts a NSECX salt to uppercase and returns "-" when it is empty.
 func saltToString(s string) string {
-	if len(s) == 0 {
+	if s == "" {
 		return "-"
 	}
 	return strings.ToUpper(s)