Struct ExprExt

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pub struct ExprExt(/* private fields */);

Available on crate feature compiler only.

Expand description

Configuration for extended vectorscan parameters.

These parameters cover various types of fuzzy search as well as input subsetting features. See Extended Parameters for a further reference.

This structure may be passed in when building a database with ExpressionSet::with_exts(), or used to interrogate a single expression with Expression::ext_info().

Like many other flags arguments, this struct also supports ops::BitOr and the | operator for composition:

 use vectorscan::{expression::*, flags::*, matchers::*, sources::*};

 // Apply extended configuration to one version of the pattern, but not the other:
 let a: Expression = "ab".parse()?;
 let ext = ExprExt::from_min_offset(3) | ExprExt::from_max_offset(15);
 let set = ExpressionSet::from_exprs([&a, &a])
   .with_exts([Some(&ext), None])
   .with_ids([ExprId(1), ExprId(2)])
   .compile(Mode::BLOCK)?;
 let mut scratch = set.allocate_scratch()?;

 let msg: ByteSlice = "ab   ab                ab".into();

 let mut matches: Vec<ExpressionIndex> = Vec::new();
 scratch.scan_sync(&set, msg, |m| {
   matches.push(m.id);
   MatchResult::Continue
 })?;

 // The configured pattern misses out on the first and last match of "ab":
 assert_eq!(&matches, &[
   ExpressionIndex(2), ExpressionIndex(1), ExpressionIndex(2), ExpressionIndex(2),
 ]);

Implementations§

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impl ExprExt

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pub fn zeroed() -> Self

Generate an empty instance with all features disabled.

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pub fn from_min_offset(x: usize) -> Self

The minimum end offset in the data stream at which this expression should match successfully.

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pub fn from_max_offset(x: usize) -> Self

The maximum end offset in the data stream at which this expression should match successfully.

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pub fn from_min_length(x: usize) -> Self

The minimum match length (from start to end) required to successfully match this expression.

This is one alternative to the use of Flags::ALLOWEMPTY.

This does not require Flags::SOM_LEFTMOST:

 use vectorscan::{expression::*, flags::*, matchers::*, sources::*};

 let a: Expression = "a.*b".parse()?;
 let ext = ExprExt::from_min_length(4);
 let set = ExpressionSet::from_exprs([&a, &a])
   // #1 has no min_length, #2 does:
   .with_exts([None, Some(&ext)])
   .with_ids([ExprId(1), ExprId(2)])
   .compile(Mode::BLOCK)?;
 let mut scratch = set.allocate_scratch()?;

 let msg: ByteSlice = "   ab   ab   ".into();

 let mut matches: Vec<(u32, &str)> = Vec::new();
 scratch.scan_sync(&set, msg, |m| {
   matches.push((m.id.0, unsafe { m.source.as_str() }));
   MatchResult::Continue
 })?;

 assert_eq!(&matches, &[
   // Without min_length, both matches show up:
   (1, "   ab"),
   (1, "   ab   ab"),
   // SOM_LEFTMOST is disabled, so we don't know the match start,
   // but the min_length property is correctly applied regardless:
   (2, "   ab   ab"),
 ]);