bump(github.com/benbjohnson/go-raft): d46748244f1f1830a002b8f645342426c5d73e81

third_party/github.com/benbjohnson/go-raft/command.go

@@ -0,0 +1,92 @@
+package raft
+
+import (
+	"bytes"
+	"encoding/json"
+	"fmt"
+	"io"
+	"reflect"
+)
+
+//------------------------------------------------------------------------------
+//
+// Globals
+//
+//------------------------------------------------------------------------------
+
+var commandTypes map[string]Command
+
+func init() {
+	commandTypes = map[string]Command{}
+}
+
+//------------------------------------------------------------------------------
+//
+// Typedefs
+//
+//------------------------------------------------------------------------------
+
+// A command represents an action to be taken on the replicated state machine.
+type Command interface {
+	CommandName() string
+	Apply(server *Server) (interface{}, error)
+}
+
+type CommandEncoder interface {
+	Encode(w io.Writer) error
+	Decode(r io.Reader) error
+}
+
+//------------------------------------------------------------------------------
+//
+// Functions
+//
+//------------------------------------------------------------------------------
+
+//--------------------------------------
+// Instantiation
+//--------------------------------------
+
+// Creates a new instance of a command by name.
+func newCommand(name string, data []byte) (Command, error) {
+	// Find the registered command.
+	command := commandTypes[name]
+	if command == nil {
+		return nil, fmt.Errorf("raft.Command: Unregistered command type: %s", name)
+	}
+
+	// Make a copy of the command.
+	v := reflect.New(reflect.Indirect(reflect.ValueOf(command)).Type()).Interface()
+	copy, ok := v.(Command)
+	if !ok {
+		panic(fmt.Sprintf("raft: Unable to copy command: %s (%v)", command.CommandName(), reflect.ValueOf(v).Kind().String()))
+	}
+
+	// If data for the command was passed in the decode it.
+	if data != nil {
+		if encoder, ok := copy.(CommandEncoder); ok {
+			if err := encoder.Decode(bytes.NewReader(data)); err != nil {
+				return nil, err
+			}
+		} else {
+			json.NewDecoder(bytes.NewReader(data)).Decode(copy)
+		}
+	}
+
+	return copy, nil
+}
+
+//--------------------------------------
+// Registration
+//--------------------------------------
+
+// Registers a command by storing a reference to an instance of it.
+func RegisterCommand(command Command) {
+	if command == nil {
+		panic(fmt.Sprintf("raft: Cannot register nil"))
+	} else if commandTypes[command.CommandName()] != nil {
+		panic(fmt.Sprintf("raft: Duplicate registration: %s", command.CommandName()))
+		return
+	}
+	commandTypes[command.CommandName()] = command
+}