Function PHYSFS_readBytes 

pub unsafe extern "C" fn PHYSFS_readBytes(
    handle: *mut PHYSFS_File,
    buffer: *mut c_void,
    len: PHYSFS_uint64,
) -> PHYSFS_sint64

\fn PHYSFS_sint64 PHYSFS_readBytes(PHYSFS_File *handle, void *buffer, PHYSFS_uint64 len) \brief Read bytes from a PhysicsFS filehandle

The file must be opened for reading.

\param handle handle returned from PHYSFS_openRead(). \param buffer buffer of at least (len) bytes to store read data into. \param len number of bytes being read from (handle). \return number of bytes read. This may be less than (len); this does not signify an error, necessarily (a short read may mean EOF). PHYSFS_getLastErrorCode() can shed light on the reason this might be < (len), as can PHYSFS_eof(). -1 if complete failure.

\sa PHYSFS_eof