iOS原理之Block的__block(修饰对象类型)的实现原理

//
//  BlockBasement__BlockObjectViewController.swift
//  iOS底层
//
//  Created by yanqunchao on 2019/5/19.
//  Copyright © 2019 yanqunchao. All rights reserved.
//

import UIKit

class BlockBasement__BlockObjectViewController: UIViewController {
    typealias FuncPt = ((MainBlockImpl0)->())
    
    typealias CopyFuncPt = ((MainBlockImpl0,MainBlockImpl0)->())
    typealias DisposeFuncPt = ((MainBlockImpl0)->())
    
    typealias BlockByrefObjectCopy = ((__BlockByrefPerson0,__BlockByrefPerson0)->())
    typealias BlockByrefObjectCopyDispose = ((__BlockByrefPerson0)->())
    
    /*
     * __block修饰的变量的包装类
     **/
    
    class __BlockByrefPerson0: NSObject {
        var isa:UnsafeRawPointer?
        var __forwarding:__BlockByrefPerson0?
        var flags:Int?
        var size:Int?
        var byrefCopy:BlockByrefObjectCopy?
        var byrefDispose:BlockByrefObjectCopyDispose?
        var __strongPerson:MJPerson? // 强引用
//        var __weakPerson:MJPerson? // 弱引用

        override init() {
            
        }
        
        init(isa:UnsafeRawPointer?,flags:Int,size:Int,byrefCopy:@escaping BlockByrefObjectCopy,byrefDispose:@escaping BlockByrefObjectCopyDispose, person:MJPerson) {
            super.init()
            self.isa = isa
            self.__forwarding = self
            self.flags = flags
            self.size = size
            self.byrefCopy = byrefCopy
            self.byrefDispose = byrefDispose
            self.__strongPerson = person
//            self.weakPerson = person
        }
    }
    
    /*
     * 函数实现类
     **/
    
    class BlockImpl: NSObject {
        var isa:UnsafeRawPointer?
        var Flags:Int?
        var Reserved:Int?
        var FuncPtr:FuncPt? //函数地址，
    }
    /*
     * 访问对象类型局部变量的Desc类
     **/
    
    class MainBlockDesc0: NSObject {
        var reserved:Int?
        var BlockSize:Int?
        var copy:CopyFuncPt?
        var dispose:DisposeFuncPt?
        
        init(reserved:Int,BlockSize:Int,copy:@escaping CopyFuncPt,dipose:@escaping DisposeFuncPt) {
            self.reserved = reserved
            self.BlockSize = BlockSize
            self.copy = copy
            self.dispose = dipose
        }
        override init() {
            
        }
        
    }
    
    
    /*
     * 访问auto局部变量（对象类型）的block类
     **/
    
    class MainBlockImpl0: NSObject {
        var imp: BlockImpl?
        var Desc: MainBlockDesc0?
        var person: __BlockByrefPerson0?
        init(fp:@escaping FuncPt,Desc:MainBlockDesc0,flag:Int, byrefPerson:__BlockByrefPerson0) {
            imp = BlockImpl()
//            imp!.isa = &_NSConcreateStackBlock
            imp?.Flags = 0
            imp?.FuncPtr = fp
            self.Desc = Desc
            self.person = byrefPerson
        }
        override init() {
            
        }
    }
 
    
    /*
     *block调用的函数地址
     **/
    
    func mainBlockFunc0(block:MainBlockImpl0){
        
        let person = MJPerson()
        person.age = 40
        
        block.person?.__forwarding?.__strongPerson = person
    }
    
    /*
     *当block调用copy操作的时候,也会对__BlockByrefPerson0对象进行copy操作，就会调用此函数
     *若果是强引用，就对__block修饰的对象进行retain操作，若过是__weak修饰的__block类型，就进行弱引用
     **/
    func blockByrefObjectCopy(dest:__BlockByrefPerson0,src:__BlockByrefPerson0){
        blockObjectAssign(destObjc: dest.__strongPerson!, srcObjc: src.__strongPerson!, type: 131)
    }
    
    /*
     *当__BlockByrefPerson0销毁时，会对__strongPerson进行release操作
     **/
    func blockByrefObjectDispose(src:__BlockByrefPerson0){
        blockObjectDispose(srcObjc: src.__strongPerson!, type: 131)
    }
    
    /*
     *当block调用copy操作的时候，就会调用此函数
     **/
    func mainBlockCopy0(destBlock:MainBlockImpl0,srcBlock:MainBlockImpl0){
        blockObjectAssign(destObjc: destBlock.person!, srcObjc: srcBlock.person!, type: 8) //8表示 BLOCK_FIELD_IS_BYREF
    }
    /*
     *当block从堆中移除，就会调用此函数
     **/
    func mainBlockDispose0(srcBlock:MainBlockImpl0){
        blockObjectDispose(srcObjc: srcBlock.person!, type: 3)
    }
    
    
    /*
     * 依据传入的srcObjc的类型，决定是否对其强引用.
     * 如果是strong，就会对其进行强引用（类似于retainCount + 1 的操作），如果是weak,就会对其弱引用。
     **/
    func blockObjectAssign(destObjc:AnyObject,srcObjc:AnyObject,type:Int){
        
        //            if srcObjc 为强引用 {
        //
        //            }else{
        //
        //            }
    }
    
    
    /*
     *会自动释放引用的auto变量，类似于 retainCount - 1 的操作
     **/
    func blockObjectDispose(srcObjc:AnyObject,type:Int){
        
    }
    
    
    class MJPerson: NSObject {
        var age: Int?
    }
    
    
    override func viewDidLoad() {
        super.viewDidLoad()
        self.view.backgroundColor = .white
        blockWith__BlockLocalVar()
    }
    func blockWith__BlockLocalVar(){ // // 修改局部变量的block
        
        let person = MJPerson()
        person.age = 10
        
        let byrefPerson = __BlockByrefPerson0(isa: UnsafeRawPointer(bitPattern: 0), flags: 33554432, size: MemoryLayout.size(ofValue: MainBlockImpl0.self), byrefCopy: blockByrefObjectCopy, byrefDispose: blockByrefObjectDispose, person: person)
        
        let mainBlockDesc0Data = MainBlockDesc0(reserved: 0, BlockSize: MemoryLayout.size(ofValue: MainBlockImpl0.self), copy: mainBlockCopy0,dipose: mainBlockDispose0)
        
        let block = MainBlockImpl0(fp: mainBlockFunc0, Desc: mainBlockDesc0Data,flag: 0, byrefPerson: byrefPerson)
        
        block.imp?.FuncPtr!(block)
        
        print(byrefPerson.__strongPerson!.age!)
        
    }
}