AEGP_GetOutSpecFilePath

I'm trying to write an output module plugin for Mac and I have hit a brick wall trying to open and write to a file using the unicode path provided by After Effects.

Can anyone see what I am doing wrong here:

        ERR(suites.IOOutSuite4()->AEGP_GetOutSpecFilePath(outH, &unicode_path_memH, &fileReservedB));

        ERR(suites.MemorySuite1()->AEGP_LockMemHandle(unicode_path_memH, reinterpret_cast<void **>(&unicode_pathP)));

        nsStringPath = [NSString stringWithCharacters:(unicode_pathP) length:AEGP_MAX_PATH_SIZE];

        const char *string = [nsStringPath UTF8String];

        NSLog (@"%s", string);

        NSLog (@"%@",nsStringPath);

          //check whether the output file exist, if not create a new one.

        outputFileManager = [NSFileManager defaultManager];

       if ([outputFileManager fileExistsAtPath: nsStringPath ] == NO)

        {

            NSLog (@"Output file does not exist, creating a new one");

            [outputFileManager createFileAtPath: nsStringPath

                                       contents: nil

                                     attributes: nil];

            if ([outputFileManager fileExistsAtPath: nsStringPath ] == NO)

            {

                NSLog (@"Why didn't that create a file at %@",nsStringPath);

            }

       }

        outputFileHandle  = [NSFileHandle fileHandleForWritingAtPath: nsStringPath];

       if (outputFileHandle == nil)

       {

           NSLog (@"Output file still does not exist, creating a new one didn't work");

       }

The NSLog entries show as:

9/2/17 3:39:47.119 PM After Effects[656]: /ColorManagement/*MWA/OutputTest/Characterize_00000.dpx

9/2/17 3:39:48.055 PM After Effects[656]: /ColorManagement/*MWA/OutputTest/Characterize_00000.dpx

9/2/17 3:40:43.509 PM After Effects[656]: Output file does not exist, creating a new one

9/2/17 3:40:52.085 PM After Effects[656]: Why didn't that create a file at /ColorManagement/*MWA/OutputTest/Characterize_00000.dpx

So it appears to me that I have put the unicode path into an NSString without mangling it, but it thinks the file does not exist and refusing to create one.  I thought perhaps somebody didn't like the * in the file path (which I was using just to make the directory show up at the top of the list) but I tried it without it and it still fails.

First of all does the file exist when I am given this path?  My plug in seems to create a sequence of empty files when I let it run.

Secondly should I not be using NSFileManager and NSFileHandle in a plugin?  What is the simplest way to open and write to a file on a Mac using this unicode path?

Any help or suggestions would be greatly appreciated.

Thanks.