comparison rust/hg-core/src/matchers.rs @ 51471:5633de951d34 stable

rust-matchers: raw regular expression builder

Extracting this `re_builder()` from `re_matcher()` makes it reusable
in more general cases than matching `HgPath` instances and would
help reducing code duplication in RHGitaly.

51470:406b413e3cf2

            .get_or(|| self.base.clone())
            .is_match(path.as_bytes())
    }
}

/// Returns a function that matches an `HgPath` against the given regex
/// pattern.
///
/// This can fail when the pattern is invalid or not supported by the
/// underlying engine (the `regex` crate), for instance anything with
/// back-references.
#[logging_timer::time("trace")]
fn re_matcher(pattern: &[u8]) -> PatternResult<RegexMatcher> {
    use std::io::Write;

    // The `regex` crate adds `.*` to the start and end of expressions if there
    // are no anchors, so add the start anchor.
    let mut escaped_bytes = vec![b'^', b'(', b'?', b':'];
    for byte in pattern {
        if *byte > 127 {
            write!(escaped_bytes, "\\x{:x}", *byte).unwrap();
        } else {
            escaped_bytes.push(*byte);
        }
    }
    escaped_bytes.push(b')');

    // Avoid the cost of UTF8 checking
    //
    // # Safety
    // This is safe because we escaped all non-ASCII bytes.
    let pattern_string = unsafe { String::from_utf8_unchecked(escaped_bytes) };
    let re = regex::bytes::RegexBuilder::new(&pattern_string)
        .unicode(false)
        // Big repos with big `.hgignore` will hit the default limit and
        // incur a significant performance hit. One repo's `hg status` hit
        // multiple *minutes*.
        .dfa_size_limit(50 * (1 << 20))

51471:5633de951d34

            .get_or(|| self.base.clone())
            .is_match(path.as_bytes())
    }
}

/// Return a `RegexBuilder` from a bytes pattern
///
/// This works around the fact that even if it works on byte haysacks,
/// [`regex::bytes::Regex`] still uses UTF-8 patterns.
pub fn re_bytes_builder(pattern: &[u8]) -> regex::bytes::RegexBuilder {
    use std::io::Write;

    // The `regex` crate adds `.*` to the start and end of expressions if there
    // are no anchors, so add the start anchor.
    let mut escaped_bytes = vec![b'^', b'(', b'?', b':'];
    for byte in pattern {
        if *byte > 127 {
            write!(escaped_bytes, "\\x{:x}", *byte).unwrap();
        } else {
            escaped_bytes.push(*byte);
        }
    }
    escaped_bytes.push(b')');

    // Avoid the cost of UTF8 checking
    //
    // # Safety
    // This is safe because we escaped all non-ASCII bytes.
    let pattern_string = unsafe { String::from_utf8_unchecked(escaped_bytes) };
    regex::bytes::RegexBuilder::new(&pattern_string)
}

/// Returns a function that matches an `HgPath` against the given regex
/// pattern.
///
/// This can fail when the pattern is invalid or not supported by the
/// underlying engine (the `regex` crate), for instance anything with
/// back-references.
#[logging_timer::time("trace")]
fn re_matcher(pattern: &[u8]) -> PatternResult<RegexMatcher> {
    let re = re_bytes_builder(pattern)
        .unicode(false)
        // Big repos with big `.hgignore` will hit the default limit and
        // incur a significant performance hit. One repo's `hg status` hit
        // multiple *minutes*.
        .dfa_size_limit(50 * (1 << 20))