ios - 在 iOS 上使用 RNCryptor 加密/解密大文件时的内存问题

Question

我正在尝试使用 RNCryptor 在 iOS 上加密和解密大文件 (600+MB)。在 the github我找到了关于如何在流上异步使用库的示例代码。此代码类似于 Rob Napier 在 a question about this same subject 上的回答。 .

然而，虽然我认为我正确地实现了代码，但该应用程序使用了高达 1.5 GB 的内存(在 iPad 6.1 模拟器中)。我认为代码应该阻止应用程序在内存中保留多个数据 block ？那么出了什么问题呢？

在我的 Controller 中，我创建了一个“CryptController”，我通过加密/解密请求发送消息。

  // Controller.m
  NSString *password = @"pw123";
  self.cryptor = [[CryptController alloc] initWithPassword:password];

  //start encrypting file
  [self.cryptor streamEncryptRequest:self.fileName andExtension:@"pdf" withURL:[self samplesURL]];

  //wait for encryption to finish
  NSDate *timeout = [NSDate dateWithTimeIntervalSinceNow:1];
  do {
    [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode
                             beforeDate:timeout];
  } while (![self.cryptor isFinished]);

在 CryptController 我有:

- (void)streamEncryptionDidFinish {
  if (self.cryptor.error) {
    NSLog(@"An error occurred. You cannot trust decryptedData at this point");
  }
  else {
    NSLog(@"%@ is complete. Use it as you like", [self.tempURL lastPathComponent]);
  }
  self.cryptor = nil;
  self.isFinished = YES;
}

- (void) streamEncryptRequest:(NSString *)fileName andExtension:(NSString *)ext withURL:(NSURL *)directory {

  //Make sure that this number is larger than the header + 1 block.
  int blockSize = 32 * 1024;

  NSString *encryptedFileName = [NSString stringWithFormat:@"streamEnc_%@", fileName];
  self.tempURL = [[NSFileManager defaultManager] URLForDirectory:NSDocumentDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:NO error:nil];
  self.tempURL = [self.tempURL URLByAppendingPathComponent:encryptedFileName isDirectory:NO];
  self.tempURL = [self.tempURL URLByAppendingPathExtension:@"crypt"];

  NSInputStream *decryptedStream = [NSInputStream inputStreamWithURL:[[directory URLByAppendingPathComponent:fileName isDirectory:NO] URLByAppendingPathExtension:ext]];
  NSOutputStream *cryptedStream = [NSOutputStream outputStreamWithURL:self.tempURL append:NO];

  [cryptedStream open];
  [decryptedStream open];

  __block NSMutableData *data = [NSMutableData dataWithLength:blockSize];
  __block RNEncryptor *encryptor = nil;

  dispatch_block_t readStreamBlock = ^{
    [data setLength:blockSize];
    NSInteger bytesRead = [decryptedStream read:[data mutableBytes] maxLength:blockSize];
    if (bytesRead < 0) {
      //Throw an error
    }
    else if (bytesRead == 0) {
      [encryptor finish];
    }
    else {
      [data setLength:bytesRead];
      [encryptor addData:data];
      //NSLog(@"Sent %ld bytes to encryptor", (unsigned long)bytesRead);
    }
  };

  encryptor = [[RNEncryptor alloc] initWithSettings:kRNCryptorAES256Settings
                                           password:self.password
                                            handler:^(RNCryptor *cryptor, NSData *data) {
                                              //NSLog(@"Encryptor received %ld bytes", (unsigned long)data.length);
                                              [cryptedStream write:data.bytes maxLength:data.length];
                                              if (cryptor.isFinished) {
                                                [decryptedStream close];
                                                //call my delegate that i'm finished with decrypting
                                                [self streamEncryptionDidFinish];
                                              }
                                              else {
                                                readStreamBlock();
                                              }
                                            }];

  // Read the first block to kick things off
  self.isFinished = NO;
  readStreamBlock();
}

当我使用分配工具进行分析时，我看到的分配类别持续增长是 malloc 32.50 KB、malloc 4.00 KB、NSConcreteData 和NSSubrangeData。尤其是 malloc 32.50 KB 变得很大，超过 1 GB。负责的来电者是[NSConcreteData initWithBytes:length:copy:freeWhenDone:bytesAreVM:]对于 NSConcreteData 负责的调用者是-[NSData(NSData) copyWithZone:].

当我使用 Leaks Instrument 进行分析时，没有发现任何泄漏。

我是 Objective-C 的新手，据我了解，新的 ARC 应该处理内存的分配和释放。在搜索任何与内存相关的内容时，我发现的所有信息都是假设您不使用 ARC(或者在撰写本文时它不存在)。我确定使用的是 ARC，因为当我尝试手动释放内存时会出现编译错误。

如果有人可以帮助我，将不胜感激!如果需要更多信息，我很乐意提供:)另外，我是 StackOverflow 的新手，所以如果我忽略了我应该做的任何事情，请告诉我!

Answer 1

我终于尝试了 here 给出的解决方案，它使用信号量而不是依赖于回调来等待流。这很完美:) 根据分配工具，内存使用量徘徊在 1.1 MB 左右。由于信号量语法，它可能看起来不那么整洁，但至少它完成了我需要它做的事情。

当然也欢迎其他建议:)

- (void)encryptWithSemaphore:(NSURL *)url {
  dispatch_semaphore_t semaphore = dispatch_semaphore_create(0);

  __block int total = 0;
  int blockSize = 32 * 1024;

  NSString *encryptedFile = [[url lastPathComponent] stringByDeletingPathExtension];
  NSURL *docsURL = [[NSFileManager defaultManager] URLForDirectory:NSDocumentDirectory inDomain:NSUserDomainMask appropriateForURL:nil create:NO error:nil];
  self.tempURL = [[docsURL URLByAppendingPathComponent:encryptedFile isDirectory:NO] URLByAppendingPathExtension:@"crypt"];

  NSInputStream *inputStream = [NSInputStream inputStreamWithURL:url];
  __block NSOutputStream *outputStream = [NSOutputStream outputStreamWithURL:self.tempURL append:NO];
  __block NSError *encryptionError = nil;

  [inputStream open];
  [outputStream open];

  RNEncryptor *encryptor = [[RNEncryptor alloc] initWithSettings:kRNCryptorAES256Settings
                                                        password:self.password
                                                         handler:^(RNCryptor *cryptor, NSData *data) {
                                                           @autoreleasepool {
                                                             [outputStream write:data.bytes maxLength:data.length];
                                                             dispatch_semaphore_signal(semaphore);

                                                             data = nil;
                                                             if (cryptor.isFinished) {
                                                               [outputStream close];
                                                               encryptionError = cryptor.error;
                                                               // call my delegate that I'm finished with decrypting
                                                             }
                                                           }
                                                         }];
  while (inputStream.hasBytesAvailable) {
    @autoreleasepool {
      uint8_t buf[blockSize];
      NSUInteger bytesRead = [inputStream read:buf maxLength:blockSize];
      if (bytesRead > 0) {
        NSData *data = [NSData dataWithBytes:buf length:bytesRead];

        total = total + bytesRead;
        [encryptor addData:data];

        dispatch_semaphore_wait(semaphore, DISPATCH_TIME_FOREVER);
      }
    }
  }

  [inputStream close];
  [encryptor finish];  
}