os: Implement listdir().

os/os/__init__.py

@@ -1,11 +1,14 @@
 import ffi
 import array
+import struct
 
 
 libc = ffi.open("libc.so.6")
 
 errno = libc.var("i", "errno")
 mkdir_ = libc.func("i", "mkdir", "si")
+opendir_ = libc.func("P", "opendir", "s")
+readdir_ = libc.func("P", "readdir", "P")
 read_ = libc.func("i", "read", "ipi")
 write_ = libc.func("i", "write", "iPi")
 close_ = libc.func("i", "close", "i")
@@ -25,6 +28,23 @@ def mkdir(name, mode=0o777):
     e = mkdir_(name, mode)
     check_error(e)
 
+def listdir(path="."):
+    dir = opendir_(path)
+    if not dir:
+        check_error(e)
+    res = []
+    dirent_fmt = "iiHB256s"
+    while True:
+        dirent = readdir_(dir)
+        if not dirent:
+            break
+        dirent = ffi.as_bytearray(dirent, struct.calcsize(dirent_fmt))
+        dirent = struct.unpack(dirent_fmt, dirent)
+        fname = str(dirent[4].split('\0', 1)[0], "ascii")
+        if fname != "." and fname != "..":
+            res.append(fname)
+    return res
+
 def read(fd, n):
     buf = bytearray(n)
     r = read_(fd, buf, n)

os/setup.py

@@ -1,7 +1,7 @@
 from distutils.core import setup
 
 setup(name='micropython-os',
-      version='0.0.5',
+      version='0.0.6',
       description='os module for MicroPython',
       url='https://github.com/micropython/micropython/issues/405',
       author='MicroPython Developers',

os/test_listdir.py

@@ -0,0 +1,6 @@
+import os
+
+l = os.listdir()
+print(l)
+assert "test_listdir.py" in l
+assert "os" in l