message2.go

package main

import (
        "bytes"
        "fmt"
)

type Message2 struct {
        Prefix string
        Command string
        Args []string
}

func (m Message2) String() string {
        return fmt.Sprintf("prefix: %q command: %q args %#v", m.Prefix, m.Command, m.Args)
}

func (m *Message2) UnmarshalText2(b []byte) error {

        var s [][]byte;

        if b[0] == ':' {
                s = bytes.SplitN(b, []byte{' '}, 2)
                m.Prefix = string(s[0])
                b = s[1]
        }

        s = bytes.SplitN(b, []byte{' '}, 2);
        m.Command = string(s[0]);
        b = s[1];

        for {
                if b[0] == ':' {
                        m.Args = append(m.Args, string(b))
                        break
                } else {
                        s = bytes.SplitN(b, []byte{' '}, 2)

                        if len(s) == 0 {
                                break
                        }

                        m.Args = append(m.Args, string(s[0]))

                        b = s[1]
                }
        }

        return nil
}

func (m *Message2) MarshalText2() (text []byte, err error) {
        var b bytes.Buffer

        if len(m.Prefix) > 0 {
                b.WriteByte(':')
                b.WriteString(m.Prefix)
                b.WriteByte(' ')
        }

        b.WriteString(m.Command)

        for _, arg := range m.Args  {
                b.WriteByte(' ')
                b.WriteString(arg)
        }

        return b.Bytes(), nil
}

message_test.go

package main
import (
        "testing"
)

var unmarshaltext_message_bench = []byte(":server.kevlar.net NOTICE user :*** This is a test")

func BenchmarkUnmarshalText2 (b *testing.B) {
        var m Message2
        for i := 0; i < b.N; i++ {
                m.UnmarshalText2(unmarshaltext_message_bench)
        }

}

func BenchmarkUnmarshalText (b *testing.B) {
        var m Message
        for i := 0; i < b.N; i++ {
                m.UnmarshalText(unmarshaltext_message_bench)
        }

}

output

$ go test -test.bench=.
testing: warning: no tests to run
PASS
BenchmarkUnmarshalText2   500000              5558 ns/op
BenchmarkUnmarshalText    200000             10425 ns/op
ok      irc-parser      5.610s