在iOS上使用RNCryptor加密/解密大文件时出现内存问题

Question

我正在尝试使用RNCryptor加密和解密iOS上的大文件(600 + MB).在github上,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关于同一主题的问题的答案.

但是,虽然我认为我正确实现了代码,但该应用程序使用高达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块？出了什么问题？

在我的控制器中,我创建了一个'CryptController',我用加密/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();
}

当我使用配置文件的配置仪器,配置类我看到不断增长的一致是malloc 32.50 KB,malloc 4.00 KB,NSConcreteData和NSSubrangeData.特别是malloc 32.50 KB增长大,超过1 GB.该负责调用者 [NSConcreteData initWithBytes:length:copy:freeWhenDone:bytesAreVM:] 对于NSConcreteData负责任的呼叫者 -[NSData(NSData) copyWithZone:].

当我使用泄漏仪器进行配置时,没有发现泄漏.

我是Objective-C的新手,根据我的理解,新的ARC应该处理内存的分配和释放.在搜索与内存相关的任何内容时,我发现的所有信息都假设您不使用ARC(或者在编写时它不存在).我确定使用ARC,因为当我尝试手动释放内存时,我收到编译错误.

如果有人可以帮助我,我将不胜感激!如果需要更多信息,我很乐意提供它:)另外,我是StackOverflow的新手,所以如果有什么我忽略了我应该做的事情,请通知我!

Answer 1

我终于尝试了这里给出的解决方案,它使用信号量而不是依赖回调来等待流.这完美地工作:)根据Allocations Instrument,内存使用率徘徊在1.1 MB左右.由于信号量语法,它看起来可能不那么整洁,但至少它做了我需要做的事情.

其他建议当然仍然受欢迎:)

- (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];  
}