net: remove all direct fmt and bytes imports

Once dnsMsg stops using reflect, we lose even more
indirect dependencies.

R=rsc
CC=golang-dev
https://golang.org/cl/5751043

src/pkg/net/dnsclient.go

@@ -5,8 +5,6 @@
 package net
 
 import (
-	"bytes"
-	"fmt"
 	"math/rand"
 	"sort"
 )
@@ -45,20 +43,22 @@ func reverseaddr(addr string) (arpa string, err error) {
 		return "", &DNSError{Err: "unrecognized address", Name: addr}
 	}
 	if ip.To4() != nil {
-		return fmt.Sprintf("%d.%d.%d.%d.in-addr.arpa.", ip[15], ip[14], ip[13], ip[12]), nil
+		return itoa(int(ip[15])) + "." + itoa(int(ip[14])) + "." + itoa(int(ip[13])) + "." +
+			itoa(int(ip[12])) + ".in-addr.arpa.", nil
 	}
 	// Must be IPv6
-	var buf bytes.Buffer
+	buf := make([]byte, 0, len(ip)*4+len("ip6.arpa."))
 	// Add it, in reverse, to the buffer
 	for i := len(ip) - 1; i >= 0; i-- {
-		s := fmt.Sprintf("%02x", ip[i])
-		buf.WriteByte(s[1])
-		buf.WriteByte('.')
-		buf.WriteByte(s[0])
-		buf.WriteByte('.')
+		v := ip[i]
+		buf = append(buf, hexDigit[v&0xF])
+		buf = append(buf, '.')
+		buf = append(buf, hexDigit[v>>4])
+		buf = append(buf, '.')
 	}
 	// Append "ip6.arpa." and return (buf already has the final .)
-	return buf.String() + "ip6.arpa.", nil
+	buf = append(buf, "ip6.arpa."...)
+	return string(buf), nil
 }
 
 // Find answer for name in dns message.

src/pkg/net/interface_linux.go

@@ -7,7 +7,6 @@
 package net
 
 import (
-	"fmt"
 	"os"
 	"syscall"
 	"unsafe"
@@ -194,7 +193,9 @@ func parseProcNetIGMP(path string, ifi *Interface) []Addr {
 			name = f[1]
 		case len(f[0]) == 8:
 			if ifi == nil || name == ifi.Name {
-				fmt.Sscanf(f[0], "%08x", &b)
+				for i := 0; i+1 < len(f[0]); i += 2 {
+					b[i/2], _ = xtoi2(f[0][i:i+2], 0)
+				}
 				ifma := IPAddr{IP: IPv4(b[3], b[2], b[1], b[0])}
 				ifmat = append(ifmat, ifma.toAddr())
 			}
@@ -218,10 +219,11 @@ func parseProcNetIGMP6(path string, ifi *Interface) []Addr {
 			continue
 		}
 		if ifi == nil || f[1] == ifi.Name {
-			fmt.Sscanf(f[2], "%32x", &b)
+			for i := 0; i+1 < len(f[2]); i += 2 {
+				b[i/2], _ = xtoi2(f[2][i:i+2], 0)
+			}
 			ifma := IPAddr{IP: IP{b[0], b[1], b[2], b[3], b[4], b[5], b[6], b[7], b[8], b[9], b[10], b[11], b[12], b[13], b[14], b[15]}}
 			ifmat = append(ifmat, ifma.toAddr())
-
 		}
 	}
 	return ifmat

src/pkg/net/sockopt.go

@@ -9,7 +9,6 @@
 package net
 
 import (
-	"bytes"
 	"os"
 	"syscall"
 	"time"
@@ -98,7 +97,7 @@ func setIPv4MreqToInterface(mreq *syscall.IPMreq, ifi *Interface) error {
 		}
 	}
 done:
-	if bytes.Equal(mreq.Multiaddr[:], IPv4zero.To4()) {
+	if bytesEqual(mreq.Multiaddr[:], IPv4zero.To4()) {
 		return errNoSuchMulticastInterface
 	}
 	return nil

src/pkg/net/tcpsock_posix.go

@@ -9,7 +9,6 @@
 package net
 
 import (
-	"fmt"
 	"io"
 	"os"
 	"syscall"
@@ -30,7 +29,7 @@ func sockaddrToTCP(sa syscall.Sockaddr) Addr {
 	default:
 		if sa != nil {
 			// Diagnose when we will turn a non-nil sockaddr into a nil.
-			panic(fmt.Sprintf("unexpected type in sockaddrToTCP: %T", sa))
+			panic("unexpected type in sockaddrToTCP")
 		}
 	}
 	return nil