Question

我正面临一个关于通过马赫端口发送/接收消息的奇怪延迟问题。我实现的基本概念如下：

插件创建本地端口→启动发送的远程进程消息到所述端口→返回接收的数据。

以下是插件部分：

static NSArray *returned=nil;
static CFDataRef handle_port (
   CFMessagePortRef local,
   SInt32 msgid,
   CFDataRef d,
   void *info
) {
    NSPropertyListFormat format;
    NSDictionary* ret = [NSPropertyListSerialization propertyListWithData:(NSData*)d
                                            options: NSPropertyListImmutable
                                            format: &format
                                            error: nil];
    returned=[NSArray arrayWithArray:[ret objectForKey:@"aKey"]]; //this is what I want returned from the portRet()
    NSLog(@"returned array %@",returned); 
    return NULL;     
}

NSArray* portRet(){
    CFMessagePortRef port = CFMessagePortCreateLocal(kCFAllocatorDefault, CFSTR("com.someport"), handle_port, NULL, NULL);
    CFRunLoopSourceRef source =  CFMessagePortCreateRunLoopSource(kCFAllocatorDefault, port, 0);
    CFRunLoopAddSource(CFRunLoopGetCurrent(), source, kCFRunLoopCommonModes);
    CFRelease(source);
    int r=system("/path/someExecutable"); 
    if(r !=0) NSLog(@"Program error");
    //CFMessagePortInvalidate(port);    
    //CFRelease(port);
    return returned; // always returns nil
}

someExecutable代码的重要部分如下：

int main(){
...
CFMessagePortRef port = CFMessagePortCreateRemote(NULL, CFSTR("com.someport"));
    if(port == NULL) exit(1);
    CFDataRef d=CFPropertyListCreateData(kCFAllocatorDefault,[NSDictionary dictionaryWithObject:anArray forKey:@"aKey"], kCFPropertyListXMLFormat_v1_0, 0, NULL);
    CFMessagePortSendRequest (port, 0, d, 0, 0, NULL, NULL);
    NSLog(@"Program is about to exit");
    CFRelease(d);
...
    exit(0);
}

来自远程进程的消息正常发送，但在进程结束并且portRet()返回空值后，回调称为。如果我使portRet()函数内的端口无效，则永远不会收到该消息。

我无法弄清楚这种延迟发生的原因。我想要实现的是在portRet()返回之前调用端口回调。我还尝试使用主调度队列而不是CFRunLoopSource来进行端口的回调调度：

CFMessagePortSetDispatchQueue(port, dispatch_get_main_queue());

但结果几乎相同。我不确定我做错了什么。非常感谢您的帮助。

Answer 1

您需要在portRet中运行运行循环，直到第二个进程返回一个值。例如：

SInt32 runLoopRunReturnValue = CFRunLoopRunInMode(kCFRunLoopDefaultMode, CFDateGetTimeIntervalSinceDate((__bridge CFDateRef)[NSDate distantFuture], (__bridge CFDateRef)[NSDate date]), true);

if (runLoopRunReturnValue == kCFRunLoopRunHandledSource)
    return returned;
else {
    // Throw exception or whatever
    // (although this will never be called using the above implementation
    // since [NSDate distantFuture] is wayy into the future...)
}

CFMessagePort很奇怪

1 个答案: