Mercurial > hg
view tests/test-narrow-patch.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 | dc01484606da |
children |
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#testcases flat tree $ . "$TESTDIR/narrow-library.sh" #if tree $ cat << EOF >> $HGRCPATH > [experimental] > treemanifest = 1 > EOF #endif create full repo $ hg init master $ cd master $ mkdir inside $ echo inside > inside/f1 $ mkdir outside $ echo outside > outside/f1 $ hg ci -Aqm 'initial' $ echo modified > inside/f1 $ hg ci -qm 'modify inside' $ echo modified > outside/f1 $ hg ci -qm 'modify outside' $ cd .. $ hg clone --narrow ssh://user@dummy/master narrow --include inside requesting all changes adding changesets adding manifests adding file changes added 3 changesets with 2 changes to 1 files new changesets *:* (glob) updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ cd narrow Can show patch touching paths outside $ hg log -p changeset: 2:* (glob) tag: tip user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: modify outside changeset: 1:* (glob) user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: modify inside diff -r * -r * inside/f1 (glob) --- a/inside/f1 Thu Jan 01 00:00:00 1970 +0000 +++ b/inside/f1 Thu Jan 01 00:00:00 1970 +0000 @@ -1,1 +1,1 @@ -inside +modified changeset: 0:* (glob) user: test date: Thu Jan 01 00:00:00 1970 +0000 summary: initial diff -r 000000000000 -r * inside/f1 (glob) --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/inside/f1 Thu Jan 01 00:00:00 1970 +0000 @@ -0,0 +1,1 @@ +inside $ hg status --rev 1 --rev 2 Can show copies inside the narrow clone $ hg cp inside/f1 inside/f2 $ hg diff --git diff --git a/inside/f1 b/inside/f2 copy from inside/f1 copy to inside/f2