from pypy.interpreter.gateway import unwrap_spec
from pypy.rpython.lltypesystem import rffi
from pypy.translator.tool.cbuild import ExternalCompilationInfo
import sys

if sys.platform.startswith('darwin'):
    eci = ExternalCompilationInfo()
else:
    eci = ExternalCompilationInfo(libraries=['crypt'])
c_crypt = rffi.llexternal('crypt', [rffi.CCHARP, rffi.CCHARP], rffi.CCHARP,
                          compilation_info=eci, threadsafe=False)

@unwrap_spec(word=str, salt=str)
def crypt(space, word, salt):
    """word will usually be a user's password. salt is a 2-character string
    which will be used to select one of 4096 variations of DES. The characters
    in salt must be either ".", "/", or an alphanumeric character. Returns
    the hashed password as a string, which will be composed of characters from
    the same alphabet as the salt."""
    res = c_crypt(word, salt)
    if not res:
        return space.w_None
    str_res = rffi.charp2str(res)
    return space.wrap(str_res)
