Mercurial > hg
view tests/test-addremove-similar.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 | 5abc47d4ca6b |
children | 5b89626c11e9 |
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$ hg init rep; cd rep $ touch empty-file $ "$PYTHON" -c 'for x in range(10000): print(x)' > large-file $ hg addremove adding empty-file adding large-file $ hg commit -m A $ rm large-file empty-file $ "$PYTHON" -c 'for x in range(10,10000): print(x)' > another-file $ hg addremove -s50 adding another-file removing empty-file removing large-file recording removal of large-file as rename to another-file (99% similar) $ hg commit -m B comparing two empty files caused ZeroDivisionError in the past $ hg update -C 0 2 files updated, 0 files merged, 1 files removed, 0 files unresolved $ rm empty-file $ touch another-empty-file $ hg addremove -s50 adding another-empty-file removing empty-file $ cd .. $ hg init rep2; cd rep2 $ "$PYTHON" -c 'for x in range(10000): print(x)' > large-file $ "$PYTHON" -c 'for x in range(50): print(x)' > tiny-file $ hg addremove adding large-file adding tiny-file $ hg commit -m A $ "$PYTHON" -c 'for x in range(70): print(x)' > small-file $ rm tiny-file $ rm large-file $ hg addremove -s50 removing large-file adding small-file removing tiny-file recording removal of tiny-file as rename to small-file (82% similar) $ hg commit -m B should be sorted by path for stable result $ for i in `"$PYTHON" $TESTDIR/seq.py 0 9`; do > cp small-file $i > done $ rm small-file $ hg addremove adding 0 adding 1 adding 2 adding 3 adding 4 adding 5 adding 6 adding 7 adding 8 adding 9 removing small-file recording removal of small-file as rename to 0 (100% similar) recording removal of small-file as rename to 1 (100% similar) recording removal of small-file as rename to 2 (100% similar) recording removal of small-file as rename to 3 (100% similar) recording removal of small-file as rename to 4 (100% similar) recording removal of small-file as rename to 5 (100% similar) recording removal of small-file as rename to 6 (100% similar) recording removal of small-file as rename to 7 (100% similar) recording removal of small-file as rename to 8 (100% similar) recording removal of small-file as rename to 9 (100% similar) $ hg commit -m '10 same files' pick one from many identical files $ cp 0 a $ rm `"$PYTHON" $TESTDIR/seq.py 0 9` $ hg addremove removing 0 removing 1 removing 2 removing 3 removing 4 removing 5 removing 6 removing 7 removing 8 removing 9 adding a recording removal of 0 as rename to a (100% similar) $ hg revert -aq pick one from many similar files $ cp 0 a $ for i in `"$PYTHON" $TESTDIR/seq.py 0 9`; do > echo $i >> $i > done $ hg commit -m 'make them slightly different' $ rm `"$PYTHON" $TESTDIR/seq.py 0 9` $ hg addremove -s50 removing 0 removing 1 removing 2 removing 3 removing 4 removing 5 removing 6 removing 7 removing 8 removing 9 adding a recording removal of 0 as rename to a (99% similar) $ hg commit -m 'always the same file should be selected' should all fail $ hg addremove -s foo abort: similarity must be a number [255] $ hg addremove -s -1 abort: similarity must be between 0 and 100 [255] $ hg addremove -s 1e6 abort: similarity must be between 0 and 100 [255] $ cd .. Issue1527: repeated addremove causes Abort $ hg init rep3; cd rep3 $ mkdir d $ echo a > d/a $ hg add d/a $ hg commit -m 1 $ mv d/a d/b $ hg addremove -s80 removing d/a adding d/b recording removal of d/a as rename to d/b (100% similar) $ hg debugstate r 0 0 1970-01-01 00:00:00 d/a a 0 -1 unset d/b copy: d/a -> d/b $ mv d/b c no copies found here (since the target isn't in d $ hg addremove -s80 d removing d/b copies here $ hg addremove -s80 adding c recording removal of d/a as rename to c (100% similar) $ cd ..