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我正在尝试使用 RNCryptor 在 iOS 上加密和解密大文件（600+MB）。在github 上，我找到了有关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。

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块？那么出了什么问题呢？

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();
}

当我使用分配工具进行分析时，我看到持续增长的分配类别是malloc 32.50 KB、和。尤其是增长很大，超过 1 GB。负责的调用者是 负责的调用者是 。malloc 4.00 KBNSConcreteDataNSSubrangeDatamalloc 32.50 KB[NSConcreteData initWithBytes:length:copy:freeWhenDone:bytesAreVM:]NSConcreteData-[NSData(NSData) copyWithZone:]

当我使用泄漏仪器进行分析时，没有发现泄漏。

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！

4

4 回答 4

7

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，仍然欢迎其他建议:)

- (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];  
}
于 2013-03-12T11:04:30.980 回答
4

赶紧跑：

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

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

麻烦：堆栈正在增长，自动释放拉取不会执行缓冲区释放。

解决方案：在同一个队列中添加异步..这将使当前块完成执行。

这是代码：

__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();
});
于 2013-05-07T11:15:18.087 回答
0

我可能错了，但我认为您的do...while循环会阻止自动释放池足够频繁地耗尽。

你为什么要使用这个循环来等待解密器完成？您应该使用完成块来通知您的控制器 drcryptor 已完成。

（顺便说一句，欢迎来到 SO，你的问题问得很好，非常感谢）。

于 2013-03-11T11:01:04.897 回答
0

我可能又错了，但是在您的readStreamBlock, 中data应该是块的参数，而不是对在其__block NSMutableData外部声明的引用。如您所见，RNEncryptor处理程序提供了自己的data变量，这与您自己声明的变量不同。

理想情况下，将所有readStreamBlock内容直接放在处理程序中，甚至无需将其声明为块。

于 2013-03-11T12:49:33.280 回答