refactor command command

database/router.go

@@ -1,36 +1,67 @@
 package database
 
 import (
+	"github.com/hdt3213/godis/interface/redis"
+	"github.com/hdt3213/godis/redis/protocol"
 	"strings"
 )
 
 var cmdTable = make(map[string]*command)
 
 type command struct {
+	name     string
 	executor ExecFunc
-	prepare  PreFunc // return related keys command
-	undo     UndoFunc
-	arity    int // allow number of args, arity < 0 means len(args) >= -arity
-	flags    int
+	// prepare returns related keys command
+	prepare PreFunc
+	// undo generates undo-log before command actually executed, in case the command needs to be rolled back
+	undo UndoFunc
+	// arity means allowed number of cmdArgs, arity < 0 means len(args) >= -arity.
+	// for example: the arity of `get` is 2, `mget` is -2
+	arity int
+	flags int
+	extra *commandExtra
 }
 
+type commandExtra struct {
+	signs    []string
+	firstKey int
+	lastKey  int
+	keyStep  int
+}
+
+const flagWrite = 0
+
 const (
-	flagWrite    = 0
-	flagReadOnly = 1
+	flagReadOnly = 1 << iota
+	flagSpecial  // command invoked in Exec
 )
 
-// RegisterCommand registers a new command
-// arity means allowed number of cmdArgs, arity < 0 means len(args) >= -arity.
-// for example: the arity of `get` is 2, `mget` is -2
-func RegisterCommand(name string, executor ExecFunc, prepare PreFunc, rollback UndoFunc, arity int, flags int) {
+// registerCommand registers a normal command, which only read or modify a limited number of keys
+func registerCommand(name string, executor ExecFunc, prepare PreFunc, rollback UndoFunc, arity int, flags int) *command {
 	name = strings.ToLower(name)
-	cmdTable[name] = &command{
+	cmd := &command{
+		name:     name,
 		executor: executor,
 		prepare:  prepare,
 		undo:     rollback,
 		arity:    arity,
 		flags:    flags,
 	}
+	cmdTable[name] = cmd
+	return cmd
+}
+
+// registerSpecialCommand registers a special command, such as publish, select, keys, flushAll
+func registerSpecialCommand(name string, arity int, flags int) *command {
+	name = strings.ToLower(name)
+	flags |= flagSpecial
+	cmd := &command{
+		name:  name,
+		arity: arity,
+		flags: flags,
+	}
+	cmdTable[name] = cmd
+	return cmd
 }
 
 func isReadOnlyCommand(name string) bool {
@@ -41,3 +72,32 @@ func isReadOnlyCommand(name string) bool {
 	}
 	return cmd.flags&flagReadOnly > 0
 }
+
+func (cmd *command) toDescReply() redis.Reply {
+	args := make([]redis.Reply, 0, 6)
+	args = append(args,
+		protocol.MakeBulkReply([]byte(cmd.name)),
+		protocol.MakeIntReply(int64(cmd.arity)))
+	if cmd.extra != nil {
+		signs := make([][]byte, len(cmd.extra.signs))
+		for i, v := range cmd.extra.signs {
+			signs[i] = []byte(v)
+		}
+		args = append(args,
+			protocol.MakeMultiBulkReply(signs),
+			protocol.MakeIntReply(int64(cmd.extra.firstKey)),
+			protocol.MakeIntReply(int64(cmd.extra.lastKey)),
+			protocol.MakeIntReply(int64(cmd.extra.keyStep)),
+		)
+	}
+	return protocol.MakeMultiRawReply(args)
+}
+
+func (cmd *command) attachCommandExtra(signs []string, firstKey int, lastKey int, keyStep int) {
+	cmd.extra = &commandExtra{
+		signs:    signs,
+		firstKey: firstKey,
+		lastKey:  lastKey,
+		keyStep:  keyStep,
+	}
+}