server/core/proto/parser.go

// Licensed to the Apache Software Foundation (ASF) under one or more
// contributor license agreements.  See the NOTICE file distributed with
// this work for additional information regarding copyright ownership.
// The ASF licenses this file to You under the Apache License, Version 2.0
// (the "License"); you may not use this file except in compliance with
// the License.  You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package proto

import (
	"encoding/json"
	"errors"
	"github.com/apache/servicecomb-service-center/pkg/registry"
	"github.com/apache/servicecomb-service-center/pkg/util"
)

var (
	errParseNilPoint  = errors.New("parse nil point")
	errTargetNilPoint = errors.New("target is nil point")
)

// new
type CreateValueFunc func() interface{}

var (
	newBytes  CreateValueFunc = func() interface{} { return []byte(nil) }
	newString CreateValueFunc = func() interface{} { return "" }
	newMap    CreateValueFunc = func() interface{} { return make(map[string]string) }

	newService         CreateValueFunc = func() interface{} { return new(registry.MicroService) }
	newInstance        CreateValueFunc = func() interface{} { return new(registry.MicroServiceInstance) }
	newRule            CreateValueFunc = func() interface{} { return new(registry.ServiceRule) }
	newDependencyRule  CreateValueFunc = func() interface{} { return new(registry.MicroServiceDependency) }
	newDependencyQueue CreateValueFunc = func() interface{} { return new(registry.ConsumerDependency) }
)

// parse
type ParseValueFunc func(src []byte, dist interface{}) error

var (
	UnParse ParseValueFunc = func(src []byte, dist interface{}) error {
		if err := check(src, dist); err != nil {
			return err
		}
		d := dist.(*interface{})
		*d = src
		return nil
	}
	TextUnmarshal ParseValueFunc = func(src []byte, dist interface{}) error {
		if err := check(src, dist); err != nil {
			return err
		}
		d := dist.(*interface{})
		*d = util.BytesToStringWithNoCopy(src)
		return nil
	}
	MapUnmarshal ParseValueFunc = func(src []byte, dist interface{}) error {
		if err := check(src, dist); err != nil {
			return err
		}
		d := dist.(*interface{})
		m := (*d).(map[string]string)
		return json.Unmarshal(src, &m)
	}
	JsonUnmarshal ParseValueFunc = func(src []byte, dist interface{}) error {
		if err := check(src, dist); err != nil {
			return err
		}
		d := dist.(*interface{})
		return json.Unmarshal(src, *d)
	}
)

type Parser interface {
	Unmarshal(src []byte) (interface{}, error)
}

type CommonParser struct {
	NewFunc  CreateValueFunc
	FromFunc ParseValueFunc
}

func (p *CommonParser) Unmarshal(src []byte) (interface{}, error) {
	v := p.NewFunc()
	if err := p.FromFunc(src, &v); err != nil {
		return nil, err
	}
	return v, nil
}

// global parser
var (
	BytesParser  = &CommonParser{newBytes, UnParse}
	StringParser = &CommonParser{newString, TextUnmarshal}
	MapParser    = &CommonParser{newMap, MapUnmarshal}

	ServiceParser         = &CommonParser{newService, JsonUnmarshal}
	InstanceParser        = &CommonParser{newInstance, JsonUnmarshal}
	RuleParser            = &CommonParser{newRule, JsonUnmarshal}
	DependencyRuleParser  = &CommonParser{newDependencyRule, JsonUnmarshal}
	DependencyQueueParser = &CommonParser{newDependencyQueue, JsonUnmarshal}
)

func check(src []byte, dist interface{}) error {
	if src == nil {
		return errParseNilPoint
	}
	if dist == nil {
		return errTargetNilPoint
	}
	return nil
}