lib/bytes: refactoring AppendXxx functions

Previously, we pass pointer to slice on AppendInt16, AppendInt32,
AppendUint16, and AppendUint32 functions.  This model of function
signature is not a Go idiom.  It is written when I am still new to
Go.

6 files changed, 123 insertions, 54 deletions

diff --git a/lib/bytes/bytes.go b/lib/bytes/bytes.go
index 6c1e6db8..f5a60f3c 100644
--- a/lib/bytes/bytes.go
+++ b/lib/bytes/bytes.go
@@ -13,39 +13,43 @@ import (
 )
 
 //
-// AppendInt16 into slice of byte.
+// AppendInt16 append an int16 value into slice of byte.
 //
-func AppendInt16(data *[]byte, v int16) {
-	*data = append(*data, byte(v>>8))
-	*data = append(*data, byte(v))
+func AppendInt16(data []byte, v int16) []byte {
+	data = append(data, byte(v>>8))
+	data = append(data, byte(v))
+	return data
 }
 
 //
-// AppendInt32 into slice of byte.
+// AppendInt32 append an int32 value into slice of byte.
 //
-func AppendInt32(data *[]byte, v int32) {
-	*data = append(*data, byte(v>>24))
-	*data = append(*data, byte(v>>16))
-	*data = append(*data, byte(v>>8))
-	*data = append(*data, byte(v))
+func AppendInt32(data []byte, v int32) []byte {
+	data = append(data, byte(v>>24))
+	data = append(data, byte(v>>16))
+	data = append(data, byte(v>>8))
+	data = append(data, byte(v))
+	return data
 }
 
 //
-// AppendUint16 into slice of byte.
+// AppendUint16 append an uint16 value into slice of byte.
 //
-func AppendUint16(data *[]byte, v uint16) {
-	*data = append(*data, byte(v>>8))
-	*data = append(*data, byte(v))
+func AppendUint16(data []byte, v uint16) []byte {
+	data = append(data, byte(v>>8))
+	data = append(data, byte(v))
+	return data
 }
 
 //
-// AppendUint32 into slice of byte.
+// AppendUint32 append an uint32 value into slice of byte.
 //
-func AppendUint32(data *[]byte, v uint32) {
-	*data = append(*data, byte(v>>24))
-	*data = append(*data, byte(v>>16))
-	*data = append(*data, byte(v>>8))
-	*data = append(*data, byte(v))
+func AppendUint32(data []byte, v uint32) []byte {
+	data = append(data, byte(v>>24))
+	data = append(data, byte(v>>16))
+	data = append(data, byte(v>>8))
+	data = append(data, byte(v))
+	return data
 }
 
 //
diff --git a/lib/bytes/bytes_example_test.go b/lib/bytes/bytes_example_test.go
index dcb0e1ec..c1ef70bb 100644
--- a/lib/bytes/bytes_example_test.go
+++ b/lib/bytes/bytes_example_test.go
@@ -6,8 +6,73 @@ package bytes
 
 import (
 	"fmt"
+	"math"
 )
 
+func ExampleAppendInt16() {
+	for _, v := range []int16{math.MinInt16, 0xab, 0xabc, math.MaxInt16} {
+		out := AppendInt16([]byte{}, v)
+		fmt.Printf("%6d => %#04x => %#02v\n", v, v, out)
+	}
+	// Output:
+	// -32768 => -0x8000 => []byte{0x80, 0x00}
+	//    171 => 0x00ab => []byte{0x00, 0xab}
+	//   2748 => 0x0abc => []byte{0x0a, 0xbc}
+	//  32767 => 0x7fff => []byte{0x7f, 0xff}
+}
+
+func ExampleAppendInt32() {
+	for _, v := range []int32{math.MinInt32, 0xab, 0xabc, math.MaxInt32} {
+		out := AppendInt32([]byte{}, v)
+		fmt.Printf("%11d => %#x => %#v\n", v, v, out)
+	}
+	// Output:
+	// -2147483648 => -0x80000000 => []byte{0x80, 0x0, 0x0, 0x0}
+	//         171 => 0xab => []byte{0x0, 0x0, 0x0, 0xab}
+	//        2748 => 0xabc => []byte{0x0, 0x0, 0xa, 0xbc}
+	//  2147483647 => 0x7fffffff => []byte{0x7f, 0xff, 0xff, 0xff}
+}
+
+func ExampleAppendUint16() {
+	inputs := []uint16{0, 0xab, 0xabc, math.MaxInt16, math.MaxUint16}
+	for _, v := range inputs {
+		out := AppendUint16([]byte{}, v)
+		fmt.Printf("%5d => %#04x => %#02v\n", v, v, out)
+	}
+
+	v := inputs[4] + 1 // MaxUint16 + 1
+	out := AppendUint16([]byte{}, v)
+	fmt.Printf("%5d => %#04x => %#02v\n", v, v, out)
+
+	// Output:
+	// 0 => 0x0000 => []byte{0x00, 0x00}
+	//   171 => 0x00ab => []byte{0x00, 0xab}
+	//  2748 => 0x0abc => []byte{0x0a, 0xbc}
+	// 32767 => 0x7fff => []byte{0x7f, 0xff}
+	// 65535 => 0xffff => []byte{0xff, 0xff}
+	//     0 => 0x0000 => []byte{0x00, 0x00}
+}
+
+func ExampleAppendUint32() {
+	inputs := []uint32{0, 0xab, 0xabc, math.MaxInt32, math.MaxUint32}
+	for _, v := range inputs {
+		out := AppendUint32([]byte{}, v)
+		fmt.Printf("%11d => %#x => %#v\n", v, v, out)
+	}
+
+	v := inputs[4] + 2 // MaxUint32 + 2
+	out := AppendUint32([]byte{}, v)
+	fmt.Printf("%11d => %#x => %#v\n", v, v, out)
+
+	// Output:
+	// 0 => 0x0 => []byte{0x0, 0x0, 0x0, 0x0}
+	//         171 => 0xab => []byte{0x0, 0x0, 0x0, 0xab}
+	//        2748 => 0xabc => []byte{0x0, 0x0, 0xa, 0xbc}
+	//  2147483647 => 0x7fffffff => []byte{0x7f, 0xff, 0xff, 0xff}
+	//  4294967295 => 0xffffffff => []byte{0xff, 0xff, 0xff, 0xff}
+	//           1 => 0x1 => []byte{0x0, 0x0, 0x0, 0x1}
+}
+
 func ExampleCutUntilToken() {
 	line := []byte(`abc \def ghi`)
 
diff --git a/lib/dns/dotclient.go b/lib/dns/dotclient.go
index ff2fc630..1399973e 100644
--- a/lib/dns/dotclient.go
+++ b/lib/dns/dotclient.go
@@ -170,7 +170,7 @@ func (cl *DoTClient) Write(msg []byte) (n int, err error) {
 	lenmsg := len(msg)
 	packet := make([]byte, 0, 2+lenmsg)
 
-	libbytes.AppendUint16(&packet, uint16(lenmsg))
+	packet = libbytes.AppendUint16(packet, uint16(lenmsg))
 	packet = append(packet, msg...)
 
 	n, err = cl.conn.Write(packet)
diff --git a/lib/dns/message.go b/lib/dns/message.go
index d32f84f4..37d9c8a1 100644
--- a/lib/dns/message.go
+++ b/lib/dns/message.go
@@ -332,8 +332,8 @@ func (msg *Message) packDomainName(dname []byte, doCompress bool) (n int) {
 
 func (msg *Message) packQuestion() {
 	msg.packDomainName([]byte(msg.Question.Name), false)
-	libbytes.AppendUint16(&msg.packet, msg.Question.Type)
-	libbytes.AppendUint16(&msg.packet, msg.Question.Class)
+	msg.packet = libbytes.AppendUint16(msg.packet, msg.Question.Type)
+	msg.packet = libbytes.AppendUint16(msg.packet, msg.Question.Class)
 	msg.off += 4
 }
 
@@ -350,8 +350,8 @@ func (msg *Message) packRR(rr *ResourceRecord) {
 		msg.packDomainName([]byte(rr.Name), true)
 	}
 
-	libbytes.AppendUint16(&msg.packet, rr.Type)
-	libbytes.AppendUint16(&msg.packet, rr.Class)
+	msg.packet = libbytes.AppendUint16(msg.packet, rr.Type)
+	msg.packet = libbytes.AppendUint16(msg.packet, rr.Class)
 	msg.off += 4
 
 	if rr.Type == QueryTypeOPT {
@@ -367,7 +367,7 @@ func (msg *Message) packRR(rr *ResourceRecord) {
 	}
 
 	rr.offTTL = uint(msg.off)
-	libbytes.AppendUint32(&msg.packet, rr.TTL)
+	msg.packet = libbytes.AppendUint32(msg.packet, rr.TTL)
 	msg.off += 4
 
 	msg.packRData(rr)
@@ -417,7 +417,7 @@ func (msg *Message) packRData(rr *ResourceRecord) {
 }
 
 func (msg *Message) packA(rr *ResourceRecord) {
-	libbytes.AppendUint16(&msg.packet, rdataIPv4Size)
+	msg.packet = libbytes.AppendUint16(msg.packet, rdataIPv4Size)
 	msg.off += 2
 
 	rrText, _ := rr.Value.(string)
@@ -439,7 +439,7 @@ func (msg *Message) packA(rr *ResourceRecord) {
 
 func (msg *Message) packTextAsDomain(rr *ResourceRecord) {
 	// Reserve two octets for rdlength
-	libbytes.AppendUint16(&msg.packet, 0)
+	msg.packet = libbytes.AppendUint16(msg.packet, 0)
 	off := uint(msg.off)
 	msg.off += 2
 
@@ -451,7 +451,7 @@ func (msg *Message) packTextAsDomain(rr *ResourceRecord) {
 
 func (msg *Message) packSOA(rr *ResourceRecord) {
 	// Reserve two octets for rdlength.
-	libbytes.AppendUint16(&msg.packet, 0)
+	msg.packet = libbytes.AppendUint16(msg.packet, 0)
 	off := uint(msg.off)
 	msg.off += 2
 
@@ -460,11 +460,11 @@ func (msg *Message) packSOA(rr *ResourceRecord) {
 	n := msg.packDomainName([]byte(rrSOA.MName), true)
 	n += msg.packDomainName([]byte(rrSOA.RName), true)
 
-	libbytes.AppendUint32(&msg.packet, rrSOA.Serial)
-	libbytes.AppendInt32(&msg.packet, rrSOA.Refresh)
-	libbytes.AppendInt32(&msg.packet, rrSOA.Retry)
-	libbytes.AppendInt32(&msg.packet, rrSOA.Expire)
-	libbytes.AppendUint32(&msg.packet, rrSOA.Minimum)
+	msg.packet = libbytes.AppendUint32(msg.packet, rrSOA.Serial)
+	msg.packet = libbytes.AppendInt32(msg.packet, rrSOA.Refresh)
+	msg.packet = libbytes.AppendInt32(msg.packet, rrSOA.Retry)
+	msg.packet = libbytes.AppendInt32(msg.packet, rrSOA.Expire)
+	msg.packet = libbytes.AppendUint32(msg.packet, rrSOA.Minimum)
 
 	// Write rdlength.
 	libbytes.WriteUint16(&msg.packet, off, uint16(n+20))
@@ -476,7 +476,7 @@ func (msg *Message) packWKS(rr *ResourceRecord) {
 
 	// Write rdlength.
 	n := uint16(5 + len(rrWKS.BitMap))
-	libbytes.AppendUint16(&msg.packet, n)
+	msg.packet = libbytes.AppendUint16(msg.packet, n)
 	msg.off += 2
 
 	msg.packet = append(msg.packet, rrWKS.Address[:4]...)
@@ -491,7 +491,7 @@ func (msg *Message) packHINFO(rr *ResourceRecord) {
 	// Write rdlength.
 	n := len(rrHInfo.CPU)
 	n += len(rrHInfo.OS)
-	libbytes.AppendUint16(&msg.packet, uint16(n))
+	msg.packet = libbytes.AppendUint16(msg.packet, uint16(n))
 	msg.off += 2
 	msg.packet = append(msg.packet, rrHInfo.CPU...)
 	msg.packet = append(msg.packet, rrHInfo.OS...)
@@ -503,7 +503,7 @@ func (msg *Message) packMINFO(rr *ResourceRecord) {
 
 	// Reserve two octets for rdlength.
 	off := uint(msg.off)
-	libbytes.AppendUint16(&msg.packet, 0)
+	msg.packet = libbytes.AppendUint16(msg.packet, 0)
 	msg.off += 2
 
 	n := msg.packDomainName([]byte(rrMInfo.RMailBox), true)
@@ -518,10 +518,10 @@ func (msg *Message) packMX(rr *ResourceRecord) {
 
 	// Reserve two octets for rdlength.
 	off := uint(msg.off)
-	libbytes.AppendUint16(&msg.packet, 0)
+	msg.packet = libbytes.AppendUint16(msg.packet, 0)
 	msg.off += 2
 
-	libbytes.AppendInt16(&msg.packet, rrMX.Preference)
+	msg.packet = libbytes.AppendInt16(msg.packet, rrMX.Preference)
 	msg.off += 2
 
 	n := msg.packDomainName([]byte(rrMX.Exchange), true)
@@ -534,7 +534,7 @@ func (msg *Message) packTXT(rr *ResourceRecord) {
 	rrText, _ := rr.Value.(string)
 
 	n := uint16(len(rrText))
-	libbytes.AppendUint16(&msg.packet, n+1)
+	msg.packet = libbytes.AppendUint16(msg.packet, n+1)
 	msg.off += 2
 
 	msg.packet = append(msg.packet, byte(n))
@@ -547,14 +547,14 @@ func (msg *Message) packSRV(rr *ResourceRecord) {
 
 	// Reserve two octets for rdlength
 	off := uint(msg.off)
-	libbytes.AppendUint16(&msg.packet, 0)
+	msg.packet = libbytes.AppendUint16(msg.packet, 0)
 	msg.off += 2
 
-	libbytes.AppendUint16(&msg.packet, rrSRV.Priority)
+	msg.packet = libbytes.AppendUint16(msg.packet, rrSRV.Priority)
 	msg.off += 2
-	libbytes.AppendUint16(&msg.packet, rrSRV.Weight)
+	msg.packet = libbytes.AppendUint16(msg.packet, rrSRV.Weight)
 	msg.off += 2
-	libbytes.AppendUint16(&msg.packet, rrSRV.Port)
+	msg.packet = libbytes.AppendUint16(msg.packet, rrSRV.Port)
 	msg.off += 2
 
 	n := msg.packDomainName([]byte(rrSRV.Target), false) + 6
@@ -566,7 +566,7 @@ func (msg *Message) packSRV(rr *ResourceRecord) {
 func (msg *Message) packAAAA(rr *ResourceRecord) {
 	rrText, _ := rr.Value.(string)
 
-	libbytes.AppendUint16(&msg.packet, rdataIPv6Size)
+	msg.packet = libbytes.AppendUint16(msg.packet, rdataIPv6Size)
 	msg.off += 2
 
 	ip := net.ParseIP(rrText)
@@ -585,7 +585,7 @@ func (msg *Message) packOPT(rr *ResourceRecord) {
 
 	// Reserve two octets for rdlength.
 	off := uint(msg.off)
-	libbytes.AppendUint16(&msg.packet, 0)
+	msg.packet = libbytes.AppendUint16(msg.packet, 0)
 	msg.off += 2
 
 	if rrOPT.Length == 0 {
@@ -593,14 +593,14 @@ func (msg *Message) packOPT(rr *ResourceRecord) {
 	}
 
 	// Pack OPT rdata
-	libbytes.AppendUint16(&msg.packet, rrOPT.Code)
+	msg.packet = libbytes.AppendUint16(msg.packet, rrOPT.Code)
 
 	// Values of less than 512 bytes MUST be treated as equal to 512
 	// bytes (RFC6891 P11).
 	if rrOPT.Length < 512 {
-		libbytes.AppendUint16(&msg.packet, 512)
+		msg.packet = libbytes.AppendUint16(msg.packet, 512)
 	} else {
-		libbytes.AppendUint16(&msg.packet, rrOPT.Length)
+		msg.packet = libbytes.AppendUint16(msg.packet, rrOPT.Length)
 	}
 
 	msg.packet = append(msg.packet, rrOPT.Data[:rrOPT.Length]...)
diff --git a/lib/dns/sectionheader.go b/lib/dns/sectionheader.go
index 7008a4a4..2844fcfb 100644
--- a/lib/dns/sectionheader.go
+++ b/lib/dns/sectionheader.go
@@ -156,10 +156,10 @@ func (hdr *SectionHeader) pack() []byte {
 	packet[2] = b0
 	packet[3] = b1
 
-	libbytes.AppendUint16(&packet, hdr.QDCount)
-	libbytes.AppendUint16(&packet, hdr.ANCount)
-	libbytes.AppendUint16(&packet, hdr.NSCount)
-	libbytes.AppendUint16(&packet, hdr.ARCount)
+	packet = libbytes.AppendUint16(packet, hdr.QDCount)
+	packet = libbytes.AppendUint16(packet, hdr.ANCount)
+	packet = libbytes.AppendUint16(packet, hdr.NSCount)
+	packet = libbytes.AppendUint16(packet, hdr.ARCount)
 
 	return packet
 }
diff --git a/lib/dns/tcpclient.go b/lib/dns/tcpclient.go
index 477a3080..e88ad7d7 100644
--- a/lib/dns/tcpclient.go
+++ b/lib/dns/tcpclient.go
@@ -183,7 +183,7 @@ func (cl *TCPClient) Write(msg []byte) (n int, err error) {
 	lenmsg := len(msg)
 	packet := make([]byte, 0, 2+lenmsg)
 
-	libbytes.AppendUint16(&packet, uint16(lenmsg))
+	packet = libbytes.AppendUint16(packet, uint16(lenmsg))
 	packet = append(packet, msg...)
 
 	n, err = cl.conn.Write(packet)