Question

Given mmap’s constructor declaration:

class mmap.mmap(fileno, length[, flags[, prot[, access[, offset]]]])

How do I specify both access & offset?

The documentation states:

access may be specified in lieu of flags and prot as an optional
keyword parameter. It is an error to specify both flags, prot and
access. See the description of access above for information on how to
use this parameter.

So I’ve tried to do things like

• mmap.mmap(file_no, length, offset, access=mmap.ACCESS_COPY)

• mmap.mmap(file_no, length, access=mmap.ACCESS_COPY, offset=offset)

  m = mmap.mmap(f.fileno(), 4, access=mmap.ACCESS_COPY, offset=2)
  Traceback (most recent call last):
  File “”, line 1, in
  mmap.error: [Errno 22] Invalid argument

• mmap.mmap(file_no, length, mmap.ACCESS_COPY, offset)

But I can’t get it to work. Why is this confusing me so much?

Answer 1

This error is unrelated to access. As documented, the offset just must be a multiple of mmap.PAGESIZE or mmap.ALLOCATIONGRANULARITY.