我正在尝试使用RNCryptor加密和解密iOS上的大文件（600 + MB）。在the 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 a question about this same subject上Rob Robier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中，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，我看到的分配类别一直在增长malloc 32.50 KB，malloc 4.00 KB，NSConcreteData和NSSubrangeData。特别是malloc 32.50 KB变大，超过1 GB。负责的来电者是
[NSConcreteData initWithBytes:length:copy:freeWhenDone:bytesAreVM:]
对于NSConcreteData负责的来电者是
-[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，我们将不胜感激！如果需要更多信息，我很乐意提供:) 另外，我是StackOverflow的新手，所以如果有什么我忽略了我应该做的事情，请通知我！
答案 0 :(得分：7)
我终于尝试了给定here的解决方案，该解决方案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。
当然，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];
}
答案 1 :(得分：4)
跑步：
self.cryptorQueue = dispatch_queue_create([queueName cStringUsingEncoding:NSUTF8StringEncoding], NULL);
dispatch_async(self.cryptorQueue, ^{
readStreamBlock();
});
麻烦：堆栈正在增长，自动释放拉不会执行缓冲区释放。
解决方案：在同一队列中添加async ..这将让当前块完成执行。
以下是代码：
__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();
});
答案 2 :(得分：0)
我可能错了，但我认为你的do...while循环可以防止自动释放池频繁耗尽。
为什么使用此循环等待解密器完成？您应该使用完成块来通知控制器drcryptor已完成。
（顺便说一句，欢迎来到SO，您的问题非常好，并且非常感谢）。
答案 3 :(得分：0)
我可能会再次出错，但在您的readStreamBlock中，data应该是该块的参数，而不是对其外部声明的__block NSMutableData的引用。如您所见，RNEncryptor处理程序提供了自己的data变量，该变量与您自己声明的变量不同。
理想情况下，将所有readStreamBlock直接放在处理程序中，甚至不要将其声明为块。