Mercurial > hg
view tests/test-push-checkheads-superceed-A7.t @ 47965:f9e6f2bb721d
rhg: Don’t compare ambiguous files one byte at a time
Even though the use of `BufReader` reduces the number of syscalls to read
the file from disk, `.bytes()` yields a separate `Result` for every byte.
Creating those results and dispatching on them is most likely costly.
Instead, this commit opts for simplicity by reading the entire file into memory
and comparing a single pair of byte strings. Note that memory already needs to
contain the entire previous contents of the file, as read from the filelog.
So with an extremely large file this doubles memory use but does not make it
grow by orders of magnitude.
At first I wrote code that still avoids reading the entire file into memory
and compares one buffer at a time with `BufReader`. Find this code below for
posterity. However its correctness is subtle. I ended up preferring the
simplicity of the obviously-correct single comparison.
```rust
let mut reader = BufReader::new(fobj);
let mut expected = &contents_in_p1[..];
loop {
let buf = reader.fill_buf().when_reading_file(&fs_path)?;
if buf.is_empty() {
// Found EOF
return Ok(expected.is_empty());
} else if let Some(rest) = expected.drop_prefix(buf) {
// What we read so far matches the expected content, continue reading
let buf_len = buf.len();
reader.consume(buf_len);
expected = rest
} else {
// Found different content
return Ok(false);
}
}
```
Differential Revision: https://phab.mercurial-scm.org/D11412
author | Simon Sapin <simon.sapin@octobus.net> |
---|---|
date | Mon, 13 Sep 2021 18:48:48 +0200 |
parents | 34a46d48d24e |
children | 5996640fc6fe |
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==================================== Testing head checking code: Case A-7 ==================================== Mercurial checks for the introduction of new heads on push. Evolution comes into play to detect if existing branches on the server are being replaced by some of the new one we push. This case is part of a series of tests checking this behavior. Category A: simple case involving a branch being superceeded by another. TestCase 7: multi-changeset branch, split on multiple other, (head on its own branch), same number of head .. old-state: .. .. * 2 branch (1-changeset, and 2-changesets) .. .. new-state: .. .. * 1 new branch superceeding the head of the old-2-changesets-branch, .. * 1 new changesets on the old-1-changeset-branch superceeding the base of the other .. .. expected-result: .. .. * push allowed .. .. graph-summary: .. .. B ø⇠◔ B' .. | | .. A'◔⇢ø | .. | |/ .. C ● | .. \| .. ● $ . $TESTDIR/testlib/push-checkheads-util.sh Test setup ---------- $ mkdir A7 $ cd A7 $ setuprepos creating basic server and client repo updating to branch default 2 files updated, 0 files merged, 0 files removed, 0 files unresolved $ cd server $ mkcommit B0 $ hg up 0 0 files updated, 0 files merged, 2 files removed, 0 files unresolved $ mkcommit C0 created new head $ cd ../client $ hg pull pulling from $TESTTMP/A7/server searching for changes adding changesets adding manifests adding file changes added 2 changesets with 2 changes to 2 files (+1 heads) new changesets d73caddc5533:0f88766e02d6 (2 drafts) (run 'hg heads' to see heads, 'hg merge' to merge) $ hg up 'desc(C0)' 1 files updated, 0 files merged, 1 files removed, 0 files unresolved $ mkcommit A1 $ hg up 0 0 files updated, 0 files merged, 2 files removed, 0 files unresolved $ mkcommit B1 created new head $ hg debugobsolete `getid "desc(A0)" ` `getid "desc(A1)"` 1 new obsolescence markers obsoleted 1 changesets 1 new orphan changesets $ hg debugobsolete `getid "desc(B0)" ` `getid "desc(B1)"` 1 new obsolescence markers obsoleted 1 changesets $ hg log -G --hidden @ 25c56d33e4c4 (draft): B1 | | o a0802eb7fc1b (draft): A1 | | | o 0f88766e02d6 (draft): C0 |/ | x d73caddc5533 (draft): B0 | | | x 8aaa48160adc (draft): A0 |/ o 1e4be0697311 (public): root Actual testing -------------- $ hg push pushing to $TESTTMP/A7/server searching for changes adding changesets adding manifests adding file changes added 2 changesets with 2 changes to 2 files (+1 heads) 2 new obsolescence markers obsoleted 2 changesets $ cd ../..