[pypy-commit] cffi ctypesdef: Add two demos of ffi.ctypesdef(): this is approximately what I'd

[arigo]

Author: Armin Rigo <arigo at tunes.org>
Branch: ctypesdef
Changeset: r845:e9011d41d639
Date: 2012-08-13 16:49 +0200
http://bitbucket.org/cffi/cffi/changeset/e9011d41d639/

Log:	Add two demos of ffi.ctypesdef(): this is approximately what I'd
	like to pass.

diff --git a/demo/readdir_ctypesdef.py b/demo/readdir_ctypesdef.py
new file mode 100644
--- /dev/null
+++ b/demo/readdir_ctypesdef.py
@@ -0,0 +1,72 @@
+# A Linux-only demo
+#
+# This is a CFFI version of readdir.py using the ffi.ctypesdef() interface.
+# The differences with readdir_ctypes are highlighted with "# <--".
+import sys
+import cffi
+from cffi import ctypes    # <--
+
+if not sys.platform.startswith('linux'):
+    raise Exception("Linux-only demo")
+
+
+DIR_p = ctypes.c_void_p
+ino_t = ctypes.c_long
+off_t = ctypes.c_long
+
+class DIRENT(ctypes.Structure):
+    _fields_ = [
+        ('d_ino', ino_t),                 # inode number
+        ('d_off', off_t),                 # offset to the next dirent
+        ('d_reclen', ctypes.c_ushort),    # length of this record
+        ('d_type', ctypes.c_ubyte),       # type of file; not supported
+                                          #   by all file system types
+        ('d_name', ctypes.c_char * 256),  # filename
+        ]
+DIRENT_p = ctypes.POINTER(DIRENT)
+DIRENT_pp = ctypes.POINTER(DIRENT_p)
+
+ffi = cffi.FFI()           # <--
+C = ffi.ctypesdef(None)    # <-- equivalent to ctypes.CDLL('c')
+
+readdir_r = C.readdir_r
+readdir_r.argtypes = [DIR_p, DIRENT_p, DIRENT_pp]
+readdir_r.restype = ctypes.c_int
+
+openat = C.openat
+openat.argtypes = [ctypes.c_int, ctypes.c_char_p, ctypes.c_int]
+openat.restype = ctypes.c_int
+
+fdopendir = C.fdopendir
+fdopendir.argtypes = [ctypes.c_int]
+fdopendir.restype = DIR_p
+
+closedir = C.closedir
+closedir.argtypes = [DIR_p]
+closedir.restype = ctypes.c_int
+
+
+def walk(basefd, path):
+    print '{', path
+    dirfd = openat(basefd, path, 0)
+    if dirfd < 0:
+        # error in openat()
+        return
+    dir = fdopendir(dirfd)
+    dirent = ffi.new(DIRENT_p)       # <-- in the actual code, must use
+    result = ffi.new(DIRENT_pp)      # <-- the CFFI way, not the ctypes one
+    while True:
+        if readdir_r(dir, dirent, result):
+            # error in readdir_r()
+            break
+        if not result:
+            break
+        name = ffi.string(dirent.d_name)    # <-- CFFI way
+        print '%3d %s' % (dirent.d_type, name)
+        if dirent.d_type == 4 and name != '.' and name != '..':
+            walk(dirfd, name)
+    closedir(dir)
+    print '}'
+
+
+walk(-1, "/tmp")
diff --git a/demo/readdir_ctypesdef2.py b/demo/readdir_ctypesdef2.py
new file mode 100644
--- /dev/null
+++ b/demo/readdir_ctypesdef2.py
@@ -0,0 +1,81 @@
+# A Linux-only demo
+#
+# This combines the ffi.ctypesdef() interface with the ffi.verify()
+# interface.  The main differences with a pure ctypes interface are
+# highlighted with "# <--".
+import sys
+import cffi
+from cffi import ctypes
+
+if not sys.platform.startswith('linux'):
+    raise Exception("Linux-only demo")
+
+
+DIR = ctypes.OPAQUE          # <--
+DIR_p = ctypes.POINTER(DIR)
+
+class DIRENT(ctypes.PartialStructure):    # <--
+    _fields_ = [
+        ('d_type', ctypes.c_ubyte),       # type of file; not supported
+                                          #   by all file system types
+        ('d_name', ctypes.c_char * Ellipsis),  # filename
+        ]
+DIRENT_p = ctypes.POINTER(DIRENT)
+DIRENT_pp = ctypes.POINTER(DIRENT_p)
+
+ffi = cffi.FFI()           # <--
+C = ffi.ctypesdef()        # <--
+
+readdir_r = C.readdir_r
+readdir_r.argtypes = [DIR_p, DIRENT_p, DIRENT_pp]
+readdir_r.restype = ctypes.c_int
+
+openat = C.openat
+openat.argtypes = [ctypes.c_int, ctypes.c_char_p, ctypes.c_int]
+openat.restype = ctypes.c_int
+
+fdopendir = C.fdopendir
+fdopendir.argtypes = [ctypes.c_int]
+fdopendir.restype = DIR_p
+
+closedir = C.closedir
+closedir.argtypes = [DIR_p]
+closedir.restype = ctypes.c_int
+
+ffi.verify("""
+#ifndef _ATFILE_SOURCE
+#  define _ATFILE_SOURCE
+#endif
+#ifndef _BSD_SOURCE
+#  define _BSD_SOURCE
+#endif
+#include <fcntl.h>
+#include <sys/types.h>
+#include <dirent.h>
+""")         # <-- the whole verify() is not in ctypes, but gives API compat
+
+
+def walk(basefd, path):
+    print '{', path
+    dirfd = openat(basefd, path, 0)
+    if dirfd < 0:
+        # error in openat()
+        return
+    dir = fdopendir(dirfd)
+    dirent = ffi.new(DIRENT_p)       # <-- in the actual code, must use
+    result = ffi.new(DIRENT_pp)      # <-- the CFFI way, not the ctypes one
+    while True:
+        if readdir_r(dir, dirent, result):
+            # error in readdir_r()
+            break
+        if not result:
+            break
+        name = ffi.string(dirent.d_name)    # <-- CFFI way
+        print '%3d %s' % (dirent.d_type, name)
+        if dirent.d_type == 4 and name != '.' and name != '..':
+            walk(dirfd, name)
+    closedir(dir)
+    print '}'
+
+
+walk(-1, "/tmp")