diff --git a/client/c2c_switch.go b/client/c2c_switch.go
new file mode 100644
index 00000000..e0fb94f4
--- /dev/null
+++ b/client/c2c_switch.go
@@ -0,0 +1,81 @@
+// Code generated by client/c2c_switcher.go DO NOT EDIT.
+
+package client
+
+import (
+	"github.com/Mrs4s/MiraiGo/client/pb/msg"
+)
+
+const (
+	UnknownDecoder = iota
+	sysMsgDecoders
+	otherDecoders
+	privateMsgDecoders
+	nonSvcNotifyTroopSystemMsgDecoders
+	troopSystemMsgDecoders
+)
+
+func peekC2CDecoder(msgType int32) (decoder func(*QQClient, *msg.Message, *incomingPacketInfo), decoderType uint8) {
+	switch msgType {
+	case 9:
+		return privateMessageDecoder, privateMsgDecoders
+	case 10:
+		return privateMessageDecoder, privateMsgDecoders
+	case 31:
+		return privateMessageDecoder, privateMsgDecoders
+	case 33:
+		return troopAddMemberBroadcastDecoder, otherDecoders
+	case 35:
+		return troopSystemMessageDecoder, troopSystemMsgDecoders
+	case 36:
+		return troopSystemMessageDecoder, nonSvcNotifyTroopSystemMsgDecoders
+	case 37:
+		return troopSystemMessageDecoder, troopSystemMsgDecoders
+	case 45:
+		return troopSystemMessageDecoder, troopSystemMsgDecoders
+	case 46:
+		return troopSystemMessageDecoder, troopSystemMsgDecoders
+	case 79:
+		return privateMessageDecoder, privateMsgDecoders
+	case 84:
+		return troopSystemMessageDecoder, troopSystemMsgDecoders
+	case 85:
+		return troopSystemMessageDecoder, nonSvcNotifyTroopSystemMsgDecoders
+	case 86:
+		return troopSystemMessageDecoder, troopSystemMsgDecoders
+	case 87:
+		return troopSystemMessageDecoder, troopSystemMsgDecoders
+	case 97:
+		return privateMessageDecoder, privateMsgDecoders
+	case 120:
+		return privateMessageDecoder, privateMsgDecoders
+	case 132:
+		return privateMessageDecoder, privateMsgDecoders
+	case 133:
+		return privateMessageDecoder, privateMsgDecoders
+	case 140:
+		return tempSessionDecoder, privateMsgDecoders
+	case 141:
+		return tempSessionDecoder, privateMsgDecoders
+	case 166:
+		return privateMessageDecoder, privateMsgDecoders
+	case 167:
+		return privateMessageDecoder, privateMsgDecoders
+	case 187:
+		return systemMessageDecoder, sysMsgDecoders
+	case 188:
+		return systemMessageDecoder, sysMsgDecoders
+	case 189:
+		return systemMessageDecoder, sysMsgDecoders
+	case 190:
+		return systemMessageDecoder, sysMsgDecoders
+	case 191:
+		return systemMessageDecoder, sysMsgDecoders
+	case 208:
+		return privatePttDecoder, privateMsgDecoders
+	case 529:
+		return msgType0x211Decoder, otherDecoders
+	default:
+		return nil, UnknownDecoder
+	}
+}
diff --git a/client/c2c_switcher.go b/client/c2c_switcher.go
new file mode 100644
index 00000000..01088f55
--- /dev/null
+++ b/client/c2c_switcher.go
@@ -0,0 +1,122 @@
+//go:build ignore
+// +build ignore
+
+package main
+
+import (
+	"bytes"
+	"go/ast"
+	"go/format"
+	"go/parser"
+	"go/token"
+	"os"
+	"sort"
+	"strconv"
+	"text/template"
+)
+
+const codeTemplate = `// Code generated by client/c2c_switcher.go DO NOT EDIT.
+
+package client
+
+import (
+{{range .Imports}}	{{.}}
+{{end}}
+)
+
+const (
+	UnknownDecoder = iota
+{{range .Consts}}	{{.}}
+{{end}}
+)
+
+func peekC2CDecoder(msgType int32) (decoder func(*QQClient, *msg.Message, *incomingPacketInfo), decoderType uint8) {
+    switch msgType {
+{{range .Decoders}}	case {{.Id}}:
+		return {{.Func}}, {{.DecoderType}}
+{{end}}	default:
+        return nil, UnknownDecoder
+    }
+}`
+
+type decoder struct {
+	Id          int64
+	Func        string
+	DecoderType string
+}
+type DecoderSort []decoder
+
+func (d DecoderSort) Len() int           { return len(d) }
+func (d DecoderSort) Swap(i, j int)      { d[i], d[j] = d[j], d[i] }
+func (d DecoderSort) Less(i, j int) bool { return d[i].Id < d[j].Id }
+
+func main() {
+	type switchFile struct {
+		Imports  []string
+		Consts   []string
+		Decoders DecoderSort
+	}
+	var sf switchFile
+
+	fset := token.NewFileSet()
+	astF, err := parser.ParseFile(fset, "c2c_decoders.go", nil, parser.AllErrors|parser.ParseComments)
+	if err != nil {
+		panic(err)
+	}
+
+	sf.Imports = make([]string, 0, len(astF.Imports))
+	for _, imp := range astF.Imports {
+		sf.Imports = append(sf.Imports, imp.Path.Value)
+	}
+
+	sf.Consts = make([]string, 0, len(astF.Scope.Objects))
+	for _, obj := range astF.Scope.Objects {
+		if obj.Kind != ast.Var {
+			panic(`unknown non-variable in "c2c_decoders.go"`)
+		}
+		value := obj.Decl.(*ast.ValueSpec)
+		sf.Consts = append(sf.Consts, obj.Name)
+		for _, value := range value.Values {
+			if value, ok := value.(*ast.CompositeLit); ok {
+				for _, kv := range value.Elts {
+					if kv, ok := kv.(*ast.KeyValueExpr); ok {
+						k := kv.Key.(*ast.BasicLit)
+						v := kv.Value.(*ast.Ident)
+						sf.Decoders = append(sf.Decoders, decoder{
+							Id:          mustParseInt(k.Value),
+							Func:        v.Name,
+							DecoderType: obj.Name,
+						})
+					} else {
+						panic(`unknown key value in ` + obj.Name + ` in "c2c_decoders.go"`)
+					}
+				}
+			} else {
+				panic(`unknown non-map value in "c2c_decoders.go"`)
+			}
+		}
+	}
+	sort.Sort(sf.Decoders)
+
+	f, _ := os.OpenFile("c2c_switch.go", os.O_WRONLY|os.O_CREATE|os.O_SYNC|os.O_TRUNC, 0o755)
+	tmpl, err := template.New("template").Parse(codeTemplate)
+	if err != nil {
+		panic(err)
+	}
+	buffer := &bytes.Buffer{}
+	err = tmpl.Execute(buffer, &sf)
+	if err != nil {
+		panic(err)
+	}
+	source, _ := format.Source(buffer.Bytes())
+	f.Write(source)
+	f.Close()
+}
+
+func mustParseInt(s string) int64 {
+	i, err := strconv.ParseInt(s, 10, 32)
+	if err != nil {
+		panic(err)
+	}
+	return i
+}