swift3.0网络图片缓存原理简析

 //存储图片的文件夹 var ljFilePath:String =NSHomeDirectory() +"/Documents/"+"LJImageCache/"

#ifndef bridge_h #define bridge_h  #import <CommonCrypto/CommonDigest.h>  #endif /* bridge_h */ 

import Foundation  extension String {   var md5 : String{     let str = self.cString(using: String.Encoding.utf8)     let strLen = CC_LONG(self.lengthOfBytes(using: String.Encoding.utf8))     let digestLen = Int(CC_MD5_DIGEST_LENGTH)     let result = UnsafeMutablePointer<CUnsignedChar>.allocate(capacity: digestLen)          CC_MD5(str!, strLen, result)          let hash = NSMutableString()     for i in 0 ..< digestLen {       hash.appendFormat("%02x", result[i])     }     result.deinitialize()          return String(format: hash as String)   } } 

func urlSession(_ session: URLSession, task: URLSessionTask, didCompleteWithError error: Error?)   {     if ljcallBackClosure != nil ,let data = self.responseData{       weak var weakSelf : LJOpreationManager? = self       DispatchQueue.main.async       {         print("URLSessionDataDelegate----数据下载完毕")                  LJCacheDataManage.shared.setMemoryCache((task.currentRequest?.url?.absoluteString)!,data as Data)                  //图片缓存，根据唯一的url来作为存储数据的名称         let a = LJFileManager.shared.writeFile((task.currentRequest?.url?.absoluteString)!,data as NSData)                  print("-----写入文件成功/(a)")                  //将接收的数据结果回调到前台，用于进度展示         weakSelf?.ljcallBackClosure!(data as Data ,nil)       }     }   } 

public func retrieveImage(_ ljurl: String, _ ljcallback: @escaping OpreationClosure){          if ljurl != "" {              if LJFileManager.shared.readFileFromCache(ljurl) != nil {         //将接收的数据结果回调到前台，用于进度展示         print("获取的是Disk缓存数据哦完毕")         ljcallback(LJFileManager.shared.readFileFromCache(ljurl) as! Data,nil)       }       //首先取缓存数据，没取到的话，直接下载      else if LJCacheDataManage.shared.getMemoryCache(ljurl) != nil {         //将接收的数据结果回调到前台，用于进度展示         print("获取的是Memory缓存数据哦完毕")         ljcallback(LJCacheDataManage.shared.getMemoryCache(ljurl) ,nil)       }       else       {        _ = self.requestWebByUrl(ljurl, ljcallback)       }     }   } 

/* 写文件   fileName: 文件名称   data: 数据data */ func writeFile(_ fileName:String , _ data:NSData) -> Bool{      //let filePath:String = NSHomeDirectory() + "/Documents/" + fileName.md5   //return data.write(toFile: filePath, atomically: true)   guard self.isExistFileDir(ljFilePath) else{     return false   }      guard let filePath : String = ljFilePath + fileName.md5 else{     return false   }   return data.write(toFile: filePath, atomically: true) }  //读取文件 -（根据路径） func readFileFromCache(_ path:String) -> NSData?{      if self.isExistFileDir(ljFilePath)   {     let ljpatch = ljFilePath + path.md5     var result:NSData?     do{       result = try NSData(contentsOfFile: ljpatch, options: Data.ReadingOptions.uncached)     }catch{       return nil     }     return result   }   return nil } 

import Foundation  class LJCacheDataManage: NSObject{      //单例   public static let shared = LJCacheDataManage()      // public var diskCache =      //缓存的数据   public var memoryCache = Dictionary<String, Data>()      //返回缓存的数据   func getMemoryCache(_ urlStr : String) -> Data? {          print("返回缓存的数据------/(memoryCache[urlStr] ?? nil)")     return (memoryCache[urlStr] ?? nil)   }      //设置缓存值   func setMemoryCache(_ urlStr : String, _ data : Data){     if urlStr != "", data != nil {       memoryCache[urlStr] = data     }   } }