OSX FSEventStreamEventFlags無法正常工作

Question

我正在看文件系統事件的目錄。除了一個例外，一切似乎都正常。當我第一次創建一個文件時，它吐出它創建的文件。然後我可以刪除它，並說它已被刪除。當我再次創建相同的文件時，我同時獲得了創建和刪除的標誌。我顯然誤解了回調被調用時標記的設置方式。這裏發生了什麼？

// 
// main.c 
// GoFSEvents 
// 
// Created by Kyle Cook on 8/22/13. 
// Copyright (c) 2013 Kyle Cook. All rights reserved. 
// 

#include <CoreServices/CoreServices.h> 
#include <stdio.h> 
#include <string.h> 

void eventCallback(FSEventStreamRef stream, void* callbackInfo, size_t numEvents, void* paths, const FSEventStreamEventFlags eventFlags[], const FSEventStreamEventId eventIds[]) { 
    char **pathsList = paths; 

    for(int i = 0; i<numEvents; i++) { 
     uint32 flag = eventFlags[i]; 

     uint32 created = kFSEventStreamEventFlagItemCreated; 
     uint32 removed = kFSEventStreamEventFlagItemRemoved; 

     if(flag & removed) { 
      printf("Item Removed: %s\n", pathsList[i]); 
     } 
     else if(flag & created) { 
      printf("Item Created: %s\n", pathsList[i]); 
     } 
    } 
} 

int main(int argc, const char * argv[]) 
{ 
    CFStringRef mypath = CFSTR("/path/to/dir"); 
    CFArrayRef paths = CFArrayCreate(NULL, (const void **)&mypath, 1, NULL); 

    CFRunLoopRef loop = CFRunLoopGetMain(); 
    FSEventStreamRef stream = FSEventStreamCreate(NULL, (FSEventStreamCallback)eventCallback, NULL, paths, kFSEventStreamEventIdSinceNow, 1.0, kFSEventStreamCreateFlagFileEvents | kFSEventStreamCreateFlagNoDefer); 
    FSEventStreamScheduleWithRunLoop(stream, loop, kCFRunLoopDefaultMode); 
    FSEventStreamStart(stream); 

    CFRunLoopRun(); 

    FSEventStreamStop(stream); 
    FSEventStreamInvalidate(stream); 
    FSEventStreamRelease(stream); 

    return 0; 
} 

Answer 1

據我所知，你將不得不尋找任何kFSEventStreamEventFlagItemRemoved或kFSEventStreamEventFlagItemCreated，然後用stat()或類似的檢查，如果在事實被添加或刪除的文件。 FSEvents文檔似乎暗示。

它看起來像API是or'ing事件位在一起...所以真正它是自FSEventsListener創建以來所做的所有更改的OR。由於這似乎是這種情況，另一種選擇可能是每次創建一個新的FSEventListener（並使用coalesce timer選項）。

我做了一些谷歌搜索，但沒有找到這個問題的其他例子，甚至蘋果示例代碼，但我沒有花太多時間在它上面。

我以前使用過的kqueue API：https://gist.github.com/nielsbot/5155671（該要點是圍繞kqueue的一個OBJ-C包裝）

我改變你的代碼示例顯示每個FSEvent設置的所有標誌：

#include <CoreServices/CoreServices.h> 
#include <stdio.h> 
#include <string.h> 

static int __count = 0 ; 
void eventCallback(FSEventStreamRef stream, void* callbackInfo, size_t numEvents, void* paths, const FSEventStreamEventFlags eventFlags[], const FSEventStreamEventId eventIds[]) { 
    char **pathsList = paths; 

    printf("callback #%u\n", ++__count) ; 
    const char * flags[] = { 
     "MustScanSubDirs", 
     "UserDropped", 
     "KernelDropped", 
     "EventIdsWrapped", 
     "HistoryDone", 
     "RootChanged", 
     "Mount", 
     "Unmount", 
     "ItemCreated", 
     "ItemRemoved", 
     "ItemInodeMetaMod", 
     "ItemRenamed", 
     "ItemModified", 
     "ItemFinderInfoMod", 
     "ItemChangeOwner", 
     "ItemXattrMod", 
     "ItemIsFile", 
     "ItemIsDir", 
     "ItemIsSymlink", 
     "OwnEvent" 
    } ; 

    for(int i = 0; i<numEvents; i++) 
    { 
     printf("%u\n", i) ; 
     printf("\tpath %s\n", pathsList[i]) ; 
     printf("\tflags: ") ; 
     long bit = 1 ; 
     for(int index=0, count = sizeof(flags)/sizeof(flags[0]); index < count; ++index) 
     { 
      if ((eventFlags[i] & bit) != 0) 
      { 
       printf("%s ", flags[ index ]) ; 
      } 
      bit <<= 1 ; 
     } 
     printf("\n") ; 
    } 

    FSEventStreamFlushSync(stream) ; 

} 

int main(int argc, const char * argv[]) 
{ 
    CFStringRef path = CFStringCreateWithCString(kCFAllocatorDefault, argv[1], kCFStringEncodingUTF8) ; 
    CFArrayRef paths = CFArrayCreate(NULL, (const void **)&path, 1, &kCFTypeArrayCallBacks); 
    if (path) { CFRelease(path) ; } 

    CFRunLoopRef loop = CFRunLoopGetCurrent() ; 
    FSEventStreamRef stream = FSEventStreamCreate(NULL, (FSEventStreamCallback)eventCallback, NULL, paths, kFSEventStreamEventIdSinceNow, 0, kFSEventStreamCreateFlagFileEvents); 
    if (paths) { CFRelease(paths) ; } 

    FSEventStreamScheduleWithRunLoop(stream, loop, kCFRunLoopDefaultMode); 
    FSEventStreamStart(stream); 

    CFRunLoopRun() ; 

    FSEventStreamStop(stream); 
    FSEventStreamInvalidate(stream); 
    FSEventStreamRelease(stream); 

    return 0; 
}