Mercurial > hg
view tests/test-remotefilelog-clone.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 | 40b51c28b242 |
children | bf11ff22a9af |
line wrap: on
line source
#require no-windows $ . "$TESTDIR/remotefilelog-library.sh" $ hg init master $ cd master $ cat >> .hg/hgrc <<EOF > [remotefilelog] > server=True > EOF $ echo x > x $ hg commit -qAm x $ cd .. # shallow clone from full $ hgcloneshallow ssh://user@dummy/master shallow --noupdate streaming all changes 2 files to transfer, 227 bytes of data transferred 227 bytes in * seconds (*/sec) (glob) searching for changes no changes found $ cd shallow $ cat .hg/requires dotencode exp-dirstate-v2 (dirstate-v2 !) exp-remotefilelog-repo-req-1 fncache generaldelta persistent-nodemap (rust !) revlog-compression-zstd (zstd !) revlogv1 sparserevlog store $ hg update 1 files updated, 0 files merged, 0 files removed, 0 files unresolved 1 files fetched over 1 fetches - (1 misses, 0.00% hit ratio) over *s (glob) $ cat x x $ ls .hg/store/data $ echo foo > f $ hg add f $ hg ci -m 'local content' $ ls .hg/store/data 4a0a19218e082a343a1b17e5333409af9d98f0f5 $ cd .. # shallow clone from shallow $ hgcloneshallow ssh://user@dummy/shallow shallow2 --noupdate streaming all changes 3 files to transfer, 564 bytes of data transferred 564 bytes in * seconds (*/sec) (glob) searching for changes no changes found $ cd shallow2 $ cat .hg/requires dotencode exp-dirstate-v2 (dirstate-v2 !) exp-remotefilelog-repo-req-1 fncache generaldelta persistent-nodemap (rust !) revlog-compression-zstd (zstd !) revlogv1 sparserevlog store $ ls .hg/store/data 4a0a19218e082a343a1b17e5333409af9d98f0f5 $ hg update 2 files updated, 0 files merged, 0 files removed, 0 files unresolved $ cat x x $ cd .. # full clone from shallow Note: the output to STDERR comes from a different process to the output on STDOUT and their relative ordering is not deterministic. As a result, the test was failing sporadically. To avoid this, we capture STDERR to a file and check its contents separately. $ TEMP_STDERR=full-clone-from-shallow.stderr.tmp $ hg clone --noupdate ssh://user@dummy/shallow full 2>$TEMP_STDERR streaming all changes [100] $ cat $TEMP_STDERR remote: abort: Cannot clone from a shallow repo to a full repo. abort: pull failed on remote $ rm $TEMP_STDERR # getbundle full clone $ printf '[server]\npreferuncompressed=False\n' >> master/.hg/hgrc $ hgcloneshallow ssh://user@dummy/master shallow3 requesting all changes adding changesets adding manifests adding file changes added 1 changesets with 0 changes to 0 files new changesets b292c1e3311f updating to branch default 1 files updated, 0 files merged, 0 files removed, 0 files unresolved $ ls shallow3/.hg/store/data $ cat shallow3/.hg/requires dotencode exp-dirstate-v2 (dirstate-v2 !) exp-remotefilelog-repo-req-1 fncache generaldelta persistent-nodemap (rust !) revlog-compression-zstd (zstd !) revlogv1 sparserevlog store