libloader.py 文件源码

def locate_library (candidates, find_library=ctypes.util.find_library):
    """Tries to locate a library listed in candidates using the given
    find_library() function (or ctypes.util.find_library).
    Returns the first library found, which can be the library's name
    or the path to the library file, depending on find_library().
    Returns None if no library is found.

    arguments:
    * candidates   -- iterable with library names
    * find_library -- function that takes one positional arg (candidate)
                      and returns a non-empty str if a library has been found.
                      Any "false" value (None,False,empty str) is interpreted
                      as "library not found".
                      Defaults to ctypes.util.find_library if not given or
                      None.
    """
    if find_library is None:
        find_library = ctypes.util.find_library

    use_dll_workaround = (
        sys.platform == 'win32' and find_library is ctypes.util.find_library
    )

    for candidate in candidates:
        # Workaround for CPython 3.3 issue#16283 / pyusb #14
        if use_dll_workaround:
            candidate += '.dll'

        libname = find_library(candidate)
        if libname:
            return libname
    # -- end for
    return None