Start refactor how qemu-system commands are built

qemucli/args.go

@@ -0,0 +1,81 @@
+package qemucli
+
+import (
+	"fmt"
+	"reflect"
+
+	"github.com/pkg/errors"
+)
+
+type ArgAcceptedValue string
+
+const (
+	ArgAcceptedValueUint   ArgAcceptedValue = "uint"
+	ArgAcceptedValueString ArgAcceptedValue = "string"
+	ArgAcceptedValueMap    ArgAcceptedValue = "map"
+	ArgAcceptedValueNone   ArgAcceptedValue = "none"
+)
+
+var safeArgs = map[string]ArgAcceptedValue{
+	"accel":   ArgAcceptedValueString,
+	"boot":    ArgAcceptedValueString,
+	"m":       ArgAcceptedValueUint,
+	"smp":     ArgAcceptedValueUint,
+	"device":  ArgAcceptedValueMap,
+	"netdev":  ArgAcceptedValueMap,
+	"serial":  ArgAcceptedValueString,
+	"cdrom":   ArgAcceptedValueString,
+	"machine": ArgAcceptedValueString,
+	"cpu":     ArgAcceptedValueString,
+}
+
+type Arg interface {
+	StringKey() string
+	StringValue() string
+	ValueType() ArgAcceptedValue
+}
+
+func EncodeArgs(args []Arg) ([]string, error) {
+	var cmdArgs []string
+
+	for i, arg := range args {
+		flag, value, err := EncodeArg(arg)
+		if err != nil {
+			return nil, errors.Wrapf(err, "encode flag #%v", i)
+		}
+
+		cmdArgs = append(cmdArgs, flag)
+		if value != nil {
+			cmdArgs = append(cmdArgs, *value)
+		}
+	}
+
+	return cmdArgs, nil
+}
+
+func EncodeArg(a Arg) (string, *string, error) {
+	// We're making copies because we don't want to trust
+	// that Arg always returns the same value.
+	argKey := a.StringKey()
+	argValueType := a.ValueType()
+
+	err := validateArgKey(argKey, argValueType)
+	if err != nil {
+		return "", nil, errors.Wrap(err, "validate arg key")
+	}
+
+	if argValueType == ArgAcceptedValueNone {
+		if a.StringValue() != "" {
+			return "", nil, fmt.Errorf("arg returned a value while declaring no value (type %v)", reflect.TypeOf(a))
+		}
+
+		return argKey, nil, nil
+	}
+
+	argValueStr := a.StringValue()
+	if argValueStr == "" {
+		return "", nil, fmt.Errorf("empty string value while declaring non-empty value (type %v)", reflect.TypeOf(a))
+	}
+
+	return "-" + argKey, &argValueStr, nil
+}