On Wed, Oct 10, 2012 at 6:02 AM, Albert-Jan Roskam <fo...@yahoo.com> wrote:
>
> elif pf.startswith("lin"):
> libc = ctypes.CDLL("libc.so.6")
> fopen = libc.fdopen
> fh = fopen(ctypes.c_char_p(fn), "rb")
> fhPtr = ctypes.byref(ctypes.c_int(fh))
> buff = ctypes.create_string_buffer(lines)
> ret = libc.fread(buff, ctypes.c_int(1), ctypes.c_int(len(lines)), fhPtr)
> print buff.value
fdopen takes a file descriptor, not a filename. You're using it with a
filename like fopen (and you even called it fopen). Also, the byref
usage is incorrect. fopen() returns a pointer to a FILE. fread() needs
the pointer, not a reference to the pointer. You're giving it the
address of an int, but it expects to find a FILE. You can use
c_void_p(fh), or set the argtypes.
>>> from ctypes import *
>>> import ctypes.util
>>> libc = cdll.LoadLibrary(ctypes.util.find_library('c'))
>>> fopen = libc.fopen
>>> fread = libc.fread
>>> fread.argtypes = [c_void_p, c_size_t, c_size_t, c_void_p]
>>> fh = fopen("spam.txt", "rb")
>>> buf = create_string_buffer(128)
>>> fread(buf, 1, 128, fh)
5
>>> buf.value
'spam\n'
To use fdopen, you can get a fileno() from an open Python file object:
>>> f = open("spam.txt", "rb")
>>> fdopen = libc.fdopen
>>> fh = fdopen(f.fileno(), "rb")
>>> fread(buf, 1, 128, fh)
5
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