32768 in open() flags

[aa6]

Sorry for the question but probably you might know the answer. I'm trying to figure out open() flags for different nodejs open modes on linux and have got this:

  'r'   # Open file for reading. An exception occurs if the file does not exist.
        #32768
        # 0b1000000000000000
  'r+'  # Open file for reading and writing. An exception occurs if the file does not exist.
        #32770
        # 0b1000000000000010
  'rs'  # Open file for reading in synchronous mode. Instructs the operating system to bypass the local file system cache.
        # This is primarily useful for opening files on NFS mounts as it allows you to skip the potentially stale local cache. It has a very real impact on I/O performance so don't use this flag unless you need it.
        # Note that this doesn't turn fs.open() into a synchronous blocking call. If that's what you want then you should be using fs.openSync()
        #36864
        # 0b1001000000000000
  'rs+' # Open file for reading and writing, telling the OS to open it synchronously. See notes for 'rs' about using this with caution.
        #36866
        # 0b1001000000000010
  'w'   # Open file for writing. The file is created (if it does not exist) or truncated (if it exists).
        #32769
        # 0b1000000000000001
  'wx'  # Like 'w' but fails if path exists.
  'w+'  # Open file for reading and writing. The file is created (if it does not exist) or truncated (if it exists).
        #32770
        # 0b1000000000000010
  'wx+' # Like 'w+' but fails if path exists.
  'a'   # Open file for appending. The file is created if it does not exist.
        #33793
        # 0b1000010000000001
  'ax'  # Like 'a' but fails if path exists.
  'a+'  # Open file for reading and appending. The file is created if it does not exist.
        #33794
        # 0b1000010000000010
  'ax+' # Like 'a+' but fails if path exists.

Every flags value I've got contains 0b1000000000000000 bitmask which is 32768 in decimal or 0100000 octal. But there is no such value in require('constants') which I believe should be used instead of hardcoded values. S_IFREG is equal to 32768 but I doubt it is suitable for open flags. Could you tell me please what is this flag for and what it means? Thank you.

[aa6]

Under some unclear circumstances an open_flag 0b1000000000000000000 (262144) emegred also.

[aa6]

I've made a Travis CI test to make the matter of discussion more tangible
https://github.com/aa6/nodejs_fuse_tests/blob/master/spec/fuse-bindings_open_flags.spec.coffee

[aa6]

It is strange that open() function is never called for x modes.