[tahoe-lafs-trac-stream] [Tahoe-LAFS] #1432: Magic Folder on Mac OS X and other BSDs

[Tahoe-LAFS]

#1432: Magic Folder on Mac OS X and other BSDs
-------------------------------------+-------------------------------------
     Reporter:  davidsarah           |      Owner:
         Type:  enhancement          |     Status:  new
     Priority:  normal               |  Milestone:  undecided
    Component:  code-frontend-       |    Version:  1.8.2
  magic-folder                       |   Keywords:  fsevents mac bsd magic-
   Resolution:                       |  folder
Launchpad Bug:                       |
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Comment (by dawuud):

 Of the several steps needed to setup the Apple async filesystem events API
 we need to firstly call ''FSEventStreamCreate''.

 There's a snippet of code showing the ''FSEventStreamCreate'' being used:

 https://developer.apple.com/library/mac/documentation/Darwin/Conceptual/FSEvents_ProgGuide/UsingtheFSEventsFramework/UsingtheFSEventsFramework.html

 It doesn't look like ctypes allows the creation of c structs or objective
 c objects unless you redefine them and create them the ctypes way. So
 initially I was thinking that maybe recreating all the necessary
 structs/objective-c-objects in python ctypes manually is kinda tricky...
 and requires us to have the Apple source code or at least the .h header
 files with the struct/object definitions.

 Perhaps the pyobjc library can help us to compose these objective-c
 structures so that we can use
 ctypes to pass them into API functions. Here need a python equivalent for
 composing the CFArray of CFString which holds the filesystems paths to
 watch:

 {{{
     CFStringRef mypath = CFSTR("/path/to/scan");

     CFArrayRef pathsToWatch = CFArrayCreate(NULL, (const void **)&mypath,
 1, NULL);

     void *callbackInfo = NULL; // could put stream-specific data here.

     FSEventStreamRef stream;

     CFAbsoluteTime latency = 3.0; /* Latency in seconds */

 }}}

 The pyobjc module requies xcode and when I pip installed it after properly
 installed xcode it downloaded many more modules; I wonder if this thing is
 too heavy weight. We probably want to avoid heavyweight dependencies?

 I also discovered that google wrote a ctypes wrapper for Apple objective-c
 structures in this project:

 https://github.com/google/grr
 https://github.com/google/grr/blob/master/grr/client/osx/objc.py

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Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/1432#comment:18>
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