comparison mercurial/posix.py @ 14927:2aa3e07b2f07

posix, windows: introduce cachestat

This class contains a stat result, and possibly other file info to reliably
determine between two points in time whether a file has changed.

Uniquely identifying a file gives us that reliability because we either
atomic rename or append. So one of two will happen: the file 'id' will change,
or the size of the file will change.

posix implements it simply by calling os.stat() and checking if the result
has st_ino.

For now on Windows we always assume the path is uncacheable. This can be
improved on NTFS due to file IDs: http://msdn.microsoft.com/en-us/library/aa363788(v=vs.85).aspx

So we need to find out if a file path is on an NTFS drive, for that we have:

- GetVolumeInformation, which unfortunately only works with a root path (but is available on XP)
- GetVolumeInformationByHandleW, works on a full file path but requires Vista or higher

14926:4e7e63fc685a

    Used to hide the window opened when starting asynchronous
    child process under Windows, unneeded on other systems.
    """
    pass

def executablepath():
    return None # available on Windows only

14927:2aa3e07b2f07

    Used to hide the window opened when starting asynchronous
    child process under Windows, unneeded on other systems.
    """
    pass

class cachestat(object):
    def __init__(self, path):
        self.stat = os.stat(path)

    def cacheable(self):
        return bool(self.stat.st_ino)

    def __eq__(self, other):
        try:
            return self.stat == other.stat
        except AttributeError:
            return False

    def __ne__(self, other):
        return not self == other

def executablepath():
    return None # available on Windows only