CFStreamCreatePairWithSocketToHost iOS 中的内存泄漏

Question

我使用NSInputstream & NSOutputstream 建立连接并发送数据。我的流对象具有打开和关闭流的功能。我使用以下代码：

@interface Stream()
{
    NSInputStream *inputStream;
    NSOutputStream *outputStream;
}

-(id)init
{
    self = [super init];
    if (self)
    {
        inputStream = nil;
        outputStream = nil;
    }
    return self;
}

-(int)streamOpenWithIp:(NSString *)ip withPortNumber:(int)portNumber;
{
        CFReadStreamRef readStream;
        CFWriteStreamRef writeStream;

        CFStreamCreatePairWithSocketToHost(kCFAllocatorDefault, (__bridge CFStringRef)ip, portNumber, &readStream, &writeStream);

        if(readStream && writeStream)
        { 
            //Setup inpustream
            inputStream = (__bridge NSInputStream *)readStream;
            [inputStream setDelegate:self];
            [inputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
            [inputStream open];

            //Setup outputstream
            outputStream = (__bridge NSOutputStream *)writeStream;
            [outputStream setDelegate:self];
            [outputStream scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
            [outputStream open];
        }
}

- (int)streamClose;
{ 
        CFReadStreamSetProperty((__bridge CFReadStreamRef)(inputStream), kCFStreamPropertyShouldCloseNativeSocket, kCFBooleanTrue);
        CFReadStreamSetProperty((__bridge CFReadStreamRef)(outputStream), kCFStreamPropertyShouldCloseNativeSocket, kCFBooleanTrue);

        //Close and reset inputstream
        [inputStream setDelegate:nil];
        [inputStream close];
        [inputStream removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
        inputStream = nil;

        //Close and reset outputstream
        [outputStream setDelegate:nil];
        [outputStream close];
        [outputStream removeFromRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
        outputStream = nil;
}

当我多次打开和关闭流时，此代码工作正常。当我使用 Instruments 检查我的应用程序是否存在内存泄漏时，它说函数 CFStreamCreatePairWithSocketToHost 正在泄漏 72% 的内存。有人知道我做错了什么吗？我想不通。

Answer 1

在streamClose 方法中添加CFRelease((CFStreamRef)inputStream); 和CFRelease((CFStreamRef)outputStream);。

当CFStreamCreatePairWithSocketToHost 返回时，readStream 和 writeStream 的所有权将传递给您：

Ownership follows the Create Rule in Memory Management Programming Guide for Core Foundation.

即使使用 ARC，Core Foundation 对象也需要显式释放：

The compiler does not automatically manage the lifetimes of Core Foundation objects; you
must call CFRetain and CFRelease (or the corresponding type-specific variants) as dictated 
by the Core Foundation memory management rules (see Memory Management Programming Guide 
for Core Foundation).

或者，更改此行（以及outputStream 的对应行）：

inputStream = (__bridge NSInputStream *)readStream;

到：

inputStream = (__bridge_transfer NSInputStream *)readStream;

这是因为 readStream 有一个 ARC 不知道的未完成保留计数。通过授予 ARC 该指针的所有权，您将授予它在适当时间释放指针的权限。延伸阅读：1、2