Richard Jones schrieb: > Does anyone know how to do the equivalent of this using ctypes? > > image_data = malloc(width * height * components); > row_pointers = png_get_rows(png_ptr, info_ptr); > for (y = 0; y < height; y++) > memcpy(&image_data[width * components * y], > row_pointers[height-y-1], > width * components); > > That is, I need to get the address of a location *within* an allocated > array. This is what I've got: > > image_data = create_string_buffer(width * height * components) > address = addressof(image_data) > row_pointers = libpng.png_get_rows(png_ptr, info_ptr) > for y in xrange(height): > row = string_at(address + width * components * y) > memmove(row, row_pointers[height-y-1], width * components) > > but that's not correct. Either the addressof() or string_at() are not > working according to my understanding from the docs, because that code > segfaults. FWIW, I also tried: > > row = image_data + width * components * y > > but you can't add an int to a c_char_Array_2415600.
This feature request has now come up the second time, so I guess I will have to find a solution for it. Someone suggested a byref_at(obj, offset) method which would return a kind of pointer to 'obj' plus offset, and even provided a patch for it (on the ctypes-users lists, maybe even in the ctypes or Python SF tracker). Unfortunately that was after the feature freeze for Python 2.5. > Sadly the docs don't seem to be finished :( > > http://docs.python.org/dev/lib/ctypes-arrays-pointers.html > > This problem wouldn't have been described in the docs anyway, but keep on bugging me about the docs: Thomas -- http://mail.python.org/mailman/listinfo/python-list
