how to read, parse the SBM file format from Superbible Opengl

Question

Calling on experts, gurus, and anybody to help read and parse a file in python.

On page 751 of 6th ed. or page 800 of 7th ed. of Superbible OpenGL there is Appendix

Answer 1

The next step has to be similar to what happens in the C code:

SB6M_HEADER * header = (SB6M_HEADER *)ptr;
ptr += header->size;

You need to advance the pointer by a known size.

You have that attribute in your header class. Do you set it correctly?

But I would suggest a different approach: do not use raw Pyhon for this at all.

Instead create a wrapper using the original C code found in sb6mfile.h

and a part of the function to read the file found in sb7object.cpp

Then access this code using Python's CFFI. You pass the C header with the SBM types to the files and can use them in Python.

Once this works you can get the data back and put it in a numpy array. Usually this is a bit of work but once it works it is really robust.

Here are some links to get you started:

buffer_size = np_arr.size*np_arr.dtype.itemsize
c_buffer = ffi.buffer(cffi_arr,buffer_size)
np_arr2 = np.frombuffer(c_buffer, dtype=np_arr.dtype)

(https://ammous88.wordpress.com/2014/12/30/numpy-array-with-cffi-c-function/)

• https://docs.scipy.org/doc/numpy/reference/generated/numpy.frombuffer.html

• How to pass a Numpy array into a cffi function and how to get one back out?

• numpy.frombuffer(ffi.buffer(p, size)) https://bitbucket.org/cffi/cffi/issues/292/cant-copy-data-to-a-numpy-array#comment-31752678