util: make `mmapread()` work on Windows again
522b4d729e89 started referencing `mmap.MAP_PRIVATE`, but that's not available on
Windows, so `hg version` worked, but `make local` did not. That commit also
started calling the constructor with the fine-grained `flags` and `prot` args,
but those aren't available on Windows either[1] (though the backing C code
doesn't seem conditionalized to disallow usage of them).
I assume the change away from from the `access` arg was to provide the same
options, plus `MAP_POPULATE`. Looking at the source code[2], they're not quite
the same- `ACCESS_READ` is equivalent to `flags = MAP_SHARED` and `prot = PROT_READ`.
`MAP_PRIVATE` is only used with `ACCESS_COPY`, which allows read and write.
Therefore, we can't quite get the same baseline flags on Windows, but this was
the status quo ante and `MAP_POPULATE` is a Linux thing, so presumably it works.
I realize that typically the OS differences are abstracted into the platform
modules, but I'm leaving it here so that it is obvious what the differences are
between the platforms.
[1] https://docs.python.org/3/library/mmap.html#mmap.mmap
[2] https://github.com/python/cpython/blob/
5e0abb47886bc665eefdcc19fde985f803e49d4c/Modules/mmapmodule.c#L1539
"""utilities to assist in working with pygit2"""
from __future__ import annotations
from mercurial.node import bin, sha1nodeconstants
pygit2_module = None
def get_pygit2():
global pygit2_module
if pygit2_module is None:
try:
import pygit2 as pygit2_module # pytype: disable=import-error
pygit2_module.InvalidSpecError
except (ImportError, AttributeError):
pass
return pygit2_module
def pygit2_version():
mod = get_pygit2()
v = "N/A"
if mod:
try:
v = mod.__version__
except AttributeError:
pass
return b"(pygit2 %s)" % v.encode("utf-8")
def togitnode(n):
"""Wrapper to convert a Mercurial binary node to a unicode hexlified node.
pygit2 and sqlite both need nodes as strings, not bytes.
"""
assert len(n) == 20
return n.hex()
def fromgitnode(n):
"""Opposite of togitnode."""
assert len(n) == 40
return bin(n)
nullgit = togitnode(sha1nodeconstants.nullid)