在iOS上使用RNCryptor加密/解密大文件時出現內存問題

Question

我正在嘗試使用RNCryptor加密和解密iOS上的大文件（600 + MB）。 在github上，我找到了關於如何在流上異步使用庫的示例代碼。 此代碼類似於Rob Napier關於同一主題的問題的答案。

但是，雖然我認為我正確實現了代碼，但該應用程序使用高達1.5 GB的內存（在iPad 6.1模擬器中）。 我認為代碼應該阻止應用程序在內存中保留多個數據塊？ 出了什么問題？

在我的控制器中，我創建了一個'CryptController'，我用加密/解密請求發送消息。

  // 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();
}

當我使用分配工具進行配置時，我看到的分配類別一直在增長的是malloc 32.50 KB ， malloc 4.00 KB ， NSConcreteData和NSSubrangeData 。 特別是malloc 32.50 KB變大，超過1 GB。 負責的調用者是[NSConcreteData initWithBytes:length:copy:freeWhenDone:bytesAreVM:]對於NSConcreteData ，負責的調用者是-[NSData(NSData) copyWithZone:] 。

當我使用泄漏儀器進行配置時，沒有發現泄漏。

我是Objective-C的新手，根據我的理解，新的ARC應該處理內存的分配和釋放。 在搜索與內存相關的任何內容時，我發現的所有信息都假設您不使用ARC（或者在編寫時它不存在）。 我確定使用ARC，因為當我嘗試手動釋放內存時，我收到編譯錯誤。

如果有人可以幫助我，我將不勝感激！ 如果需要更多信息，我很樂意提供它:)另外，我是StackOverflow的新手，所以如果有什么我忽略了我應該做的事情，請通知我！

Answer 1

我終於嘗試了這里給出的解決方案，它使用信號量而不是依賴回調來等待流。 這完美地工作:)根據Allocations Instrument，內存使用率徘徊在1.1 MB左右。 由於信號量語法，它看起來可能不那么整潔，但至少它做了我需要做的事情。

其他建議當然仍然受歡迎:)

- (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];  
}

Answer 2

趕緊跑：

self.cryptorQueue = dispatch_queue_create([queueName cStringUsingEncoding:NSUTF8StringEncoding], NULL);

dispatch_async(self.cryptorQueue, ^{
        readStreamBlock();
    });

麻煩：堆棧正在增長，自動釋放拉不會執行緩沖區釋放。

解決方案：在同一隊列中添加async ..這將讓當前塊完成執行。

這是代碼：

__block NSMutableData *data = [NSMutableData dataWithLength:blockSize];
__block RNDecryptor *decryptor = nil;


dispatch_block_t readStreamBlock = ^{

    [data setLength:blockSize];

    NSInteger bytesRead = [inputStream read:[data mutableBytes] maxLength:blockSize];
    if (bytesRead < 0) {
        // Throw an error
    }
    else if (bytesRead == 0) {
        [decryptor finish];
    }
    else {

        [data setLength:bytesRead];
        [decryptor addData:data];
    }
};

decryptor = [[RNDecryptor alloc] initWithPassword:@"blah" handler:^(RNCryptor *cryptor, NSData *data) {

        [decryptedStream write:data.bytes maxLength:data.length];
        _percentStatus = (CGFloat)[[decryptedStream propertyForKey:NSStreamFileCurrentOffsetKey] intValue] / (CGFloat)_inputFileSize;
        if (cryptor.isFinished)
        {
            [decryptedStream close];
            [self decryptFinish];
        }
        else
        {
            dispatch_async(cryptor.responseQueue, ^{
                readStreamBlock();
            });
            [self decryptStatusChange];
        }

}];


// Read the first block to kick things off

decryptor.responseQueue = self.cryptorQueue;
[self decryptStart];
dispatch_async(decryptor.cryptorQueue, ^{
    readStreamBlock();
});

Answer 3

我可能錯了，但我認為你的do...while循環可以防止自動釋放池頻繁耗盡。

為什么使用此循環等待解密器完成？ 您應該使用完成塊來通知您的控制器drcryptor已完成。

（順便說一句，歡迎來到SO，你的問題非常好，並且非常感謝）。

Answer 4

我可能會再次出錯，但在readStreamBlock ， data應該是塊的參數，而不是對在其__block NSMutableData聲明的__block NSMutableData的引用。 如您所見， RNEncryptor處理程序提供了自己的data變量，這與您自己聲明的data變量不同。

理想情況下，將所有readStreamBlock直接放在處理程序中，甚至不將其聲明為塊。