pwd: add basic implementation of pwd

The only function implemented is getpwnam

pwd/metadata.txt

@@ -0,0 +1,5 @@
+srctype = micropython-lib
+type = module
+version = 0.1
+author = Riccardo Magliocchetti
+depends = ffilib

pwd/pwd.py

@@ -0,0 +1,24 @@
+import ffilib
+import uctypes
+import ustruct
+
+from ucollections import namedtuple
+
+
+libc = ffilib.libc()
+
+getpwnam_ = libc.func("P", "getpwnam", "s")
+
+
+struct_passwd = namedtuple("struct_passwd",
+    ["pw_name", "pw_passwd", "pw_uid", "pw_gid", "pw_gecos", "pw_dir", "pw_shell"])
+
+
+def getpwnam(user):
+    passwd = getpwnam_(user)
+    if not passwd:
+        raise KeyError("getpwnam(): name not found: {}".format(user))
+    passwd_fmt = "SSIISSS"
+    passwd = uctypes.bytes_at(passwd, ustruct.calcsize(passwd_fmt))
+    passwd = ustruct.unpack(passwd_fmt, passwd)
+    return struct_passwd(*passwd)

pwd/setup.py

@@ -0,0 +1,21 @@
+import sys
+# Remove current dir from sys.path, otherwise setuptools will peek up our
+# module instead of system's.
+sys.path.pop(0)
+from setuptools import setup
+sys.path.append("..")
+import optimize_upip
+
+setup(name='micropython-pwd',
+      version='0.1',
+      description='pwd module for MicroPython',
+      long_description="This is a module reimplemented specifically for MicroPython standard library,\nwith efficient and lean design in mind. Note that this module is likely work\nin progress and likely supports just a subset of CPython's corresponding\nmodule. Please help with the development if you are interested in this\nmodule.",
+      url='https://github.com/micropython/micropython-lib',
+      author='Riccardo Magliocchetti',
+      author_email='micro-python@googlegroups.com',
+      maintainer='MicroPython Developers',
+      maintainer_email='micro-python@googlegroups.com',
+      license='MIT',
+      cmdclass={'optimize_upip': optimize_upip.OptimizeUpip},
+      py_modules=['pwd'],
+      install_requires=['micropython-ffilib'])

pwd/test_getpwnam.py

@@ -0,0 +1,7 @@
+import pwd
+import os
+
+user = os.getenv('USER')
+passwd = pwd.getpwnam(user)
+assert passwd
+assert isinstance(passwd, pwd.struct_passwd)