Classes/AssetBrowser/DirectoryWatcher.m

/*
     File: DirectoryWatcher.m
 Abstract: Object used to monitor the contents of a given directory by using "kqueue": a kernel event notification mechanism.
  Version: 1.3
 
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 MAKES NO WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION
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 OPERATION ALONE OR IN COMBINATION WITH YOUR PRODUCTS.
 
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 */
 
 
#import "DirectoryWatcher.h"
 
#include <sys/types.h>
#include <sys/event.h>
#include <sys/time.h>
#include <fcntl.h>
#include <unistd.h>
 
#import <CoreFoundation/CoreFoundation.h>
 
@interface DirectoryWatcher (DirectoryWatcherPrivate)
- (BOOL)startMonitoringDirectory:(NSString *)dirPath;
- (void)kqueueFired;
@end
 
 
#pragma mark -
 
@implementation DirectoryWatcher
 
@synthesize delegate;
 
- (id)init
{
    self= [super init];
    delegate = NULL;
 
    dirFD = -1;
    kq = -1;
    dirKQRef = NULL;
    
    return self;
}
 
- (void)dealloc
{
    [self invalidate];
}
 
+ (DirectoryWatcher *)watchFolderWithPath:(NSString *)watchPath delegate:(id)watchDelegate
{
    DirectoryWatcher *retVal = NULL;
    if ((watchDelegate != NULL) && (watchPath != NULL))
    {
        DirectoryWatcher *tempManager = [[DirectoryWatcher alloc] init];
        tempManager.delegate = watchDelegate;       
        if ([tempManager startMonitoringDirectory: watchPath])
        {
            // Everything appears to be in order, so return the DirectoryWatcher.  
            // Otherwise we'll fall through and return NULL.
            retVal = tempManager;
        }
    }
    return retVal;
}
 
- (void)invalidate
{
    if (dirKQRef != NULL)
    {
        CFFileDescriptorInvalidate(dirKQRef);
        CFRelease(dirKQRef);
        dirKQRef = NULL;
        // We don't need to close the kq, CFFileDescriptorInvalidate closed it instead.
        // Change the value so no one thinks it's still live.
        kq = -1;
    }
    
    if(dirFD != -1)
    {
        close(dirFD);
        dirFD = -1;
    }
}
 
@end
 
 
#pragma mark -
 
@implementation DirectoryWatcher (DirectoryWatcherPrivate)
 
- (void)kqueueFired
{
    assert(kq >= 0);
 
    struct kevent   event;
    struct timespec timeout = {0, 0};
    int             eventCount;
    
    eventCount = kevent(kq, NULL, 0, &event, 1, &timeout);
    assert((eventCount >= 0) && (eventCount < 2));
    
    // call our delegate of the directory change
    [delegate directoryDidChange:self];
 
    CFFileDescriptorEnableCallBacks(dirKQRef, kCFFileDescriptorReadCallBack);
}
 
static void KQCallback(CFFileDescriptorRef kqRef, CFOptionFlags callBackTypes, void *info)
{
    DirectoryWatcher *obj;
    
    obj = (__bridge DirectoryWatcher *)info;
    assert([obj isKindOfClass:[DirectoryWatcher class]]);
    assert(kqRef == obj->dirKQRef);
    assert(callBackTypes == kCFFileDescriptorReadCallBack);
    
    [obj kqueueFired];
}
 
- (BOOL)startMonitoringDirectory:(NSString *)dirPath
{
    // Double initializing is not going to work...
    if ((dirKQRef == NULL) && (dirFD == -1) && (kq == -1))
    {
        // Open the directory we're going to watch
        dirFD = open([dirPath fileSystemRepresentation], O_EVTONLY);
        if (dirFD >= 0)
        {
            // Create a kqueue for our event messages...
            kq = kqueue();
            if (kq >= 0)
            {
                struct kevent eventToAdd;
                eventToAdd.ident  = dirFD;
                eventToAdd.filter = EVFILT_VNODE;
                eventToAdd.flags  = EV_ADD | EV_CLEAR;
                eventToAdd.fflags = NOTE_WRITE;
                eventToAdd.data   = 0;
                eventToAdd.udata  = NULL;
                
                int errNum = kevent(kq, &eventToAdd, 1, NULL, 0, NULL);
                if (errNum == 0)
                {
                    CFFileDescriptorContext context = { 0, (__bridge void *)(self), NULL, NULL, NULL };
                    CFRunLoopSourceRef      rls;
 
                    // Passing true in the third argument so CFFileDescriptorInvalidate will close kq.
                    dirKQRef = CFFileDescriptorCreate(NULL, kq, true, KQCallback, &context);
                    if (dirKQRef != NULL)
                    {
                        rls = CFFileDescriptorCreateRunLoopSource(NULL, dirKQRef, 0);
                        if (rls != NULL)
                        {
                            CFRunLoopAddSource(CFRunLoopGetCurrent(), rls, kCFRunLoopDefaultMode);
                            CFRelease(rls);
                            CFFileDescriptorEnableCallBacks(dirKQRef, kCFFileDescriptorReadCallBack);
                            
                            // If everything worked, return early and bypass shutting things down
                            return YES;
                        }
                        // Couldn't create a runloop source, invalidate and release the CFFileDescriptorRef
                        CFFileDescriptorInvalidate(dirKQRef);
                        CFRelease(dirKQRef);
                        dirKQRef = NULL;
                    }
                }
                // kq is active, but something failed, close the handle...
                close(kq);
                kq = -1;
            }
            // file handle is open, but something failed, close the handle...
            close(dirFD);
            dirFD = -1;
        }
    }
    return NO;
}
@end