api: introduce new regex-lite crate

Closes #961

.github/workflows/ci.yml

@@ -122,6 +122,8 @@ jobs:
     - name: Run subset of regex-automata tests
       if: matrix.build != 'win-gnu'  # Just horrifically slow.
       run: ${{ env.CARGO }} test --verbose --manifest-path regex-automata/Cargo.toml $TARGET
+    - name: Run regex-lite tests
+      run: ${{ env.CARGO }} test --verbose --manifest-path regex-lite/Cargo.toml $TARGET
 
   # This job runs a stripped down version of CI to test the MSRV. The specific
   # reason for doing this is that the regex crate's dev-dependencies tend to

Cargo.toml

@@ -22,6 +22,7 @@ members = [
   "regex-automata",
   "regex-capi",
   "regex-cli",
+  "regex-lite",
   "regex-syntax",
   "regex-test",
 ]

regex-cli/Cargo.toml

@@ -30,6 +30,7 @@ log = { version = "0.4.17", features = ["std"] }
 memmap2 = "0.5.10"
 regex = { path = ".." }
 regex-automata = { path = "../regex-automata", features = ["logging"] }
+regex-lite = { path = "../regex-lite" }
 regex-syntax = { path = "../regex-syntax" }
 tabwriter = { version = "1.2.1", features = ["ansi_formatting"] }
 textwrap = { version = "0.16.0", default-features = false }

regex-cli/args/lite.rs

@@ -0,0 +1,84 @@
+use {
+    lexopt::{Arg, Parser},
+    regex_automata::util::syntax,
+    regex_lite::Regex,
+};
+
+use crate::args::{self, Configurable, Usage};
+
+/// Exposes the configuration for the top-level `Regex` API.
+#[derive(Debug, Default)]
+pub struct Config {
+    size_limit: Option<usize>,
+}
+
+impl Config {
+    /// Builds a `Regex` from the given syntax configuration and sequence of
+    /// patterns. This returns an error is `patterns.len() != 1`.
+    ///
+    /// Note that this also returns an error if any syntax options are set
+    /// that aren't supported by `regex-lite`.
+    pub fn from_patterns(
+        &self,
+        syntax: &syntax::Config,
+        patterns: &[String],
+    ) -> anyhow::Result<Regex> {
+        anyhow::ensure!(
+            patterns.len() == 1,
+            "API-level regex requires exactly one pattern, \
+                 but {} were given",
+            patterns.len(),
+        );
+        anyhow::ensure!(
+            !syntax.get_octal(),
+            "regex-lite does not support octal mode",
+        );
+        anyhow::ensure!(
+            syntax.get_utf8(),
+            "regex-lite does not support disabling UTF-8 mode",
+        );
+        anyhow::ensure!(
+            syntax.get_unicode(),
+            "regex-lite does not support disabling Unicode mode",
+        );
+        let mut b = regex_lite::RegexBuilder::new(&patterns[0]);
+        b.case_insensitive(syntax.get_case_insensitive());
+        b.multi_line(syntax.get_multi_line());
+        b.crlf(syntax.get_crlf());
+        b.dot_matches_new_line(syntax.get_dot_matches_new_line());
+        b.swap_greed(syntax.get_swap_greed());
+        b.ignore_whitespace(syntax.get_ignore_whitespace());
+        b.nest_limit(syntax.get_nest_limit());
+        b.size_limit(self.size_limit.unwrap_or(usize::MAX));
+        b.build().map_err(anyhow::Error::from)
+    }
+}
+
+impl Configurable for Config {
+    fn configure(
+        &mut self,
+        p: &mut Parser,
+        arg: &mut Arg,
+    ) -> anyhow::Result<bool> {
+        match *arg {
+            Arg::Long("size-limit") => {
+                self.size_limit = args::parse_maybe(p, "--size-limit")?;
+            }
+            _ => return Ok(false),
+        }
+        Ok(true)
+    }
+
+    fn usage(&self) -> &[Usage] {
+        const USAGES: &'static [Usage] = &[Usage::new(
+            "--size-limit",
+            "Set a limit on heap used by a regex.",
+            r#"
+This sets a limit, in bytes, on the heap memory used by a regex.
+
+The special value 'none' indicates that no size limit should be imposed.
+"#,
+        )];
+        USAGES
+    }
+}

regex-cli/args/mod.rs

@@ -16,6 +16,7 @@ pub mod flags;
 pub mod haystack;
 pub mod hybrid;
 pub mod input;
+pub mod lite;
 pub mod meta;
 pub mod onepass;
 pub mod overlapping;

regex-cli/cmd/find/capture/mod.rs

@@ -32,6 +32,7 @@ USAGE:
 
 ENGINES:
     backtrack  Search with the bounded backtracker regex engine.
+    lite       Search with the regex-lite engine.
     meta       Search with the meta regex engine.
     onepass    Search with the one-pass DFA regex engine.
     pikevm     Search with the PikeVM regex engine.
@@ -40,6 +41,7 @@ ENGINES:
     let cmd = args::next_as_command(USAGE, p)?;
     match &*cmd {
         "backtrack" => nfa::run_backtrack(p),
+        "lite" => run_lite(p),
         "meta" => run_meta(p),
         "onepass" => dfa::run_onepass(p),
         "pikevm" => nfa::run_pikevm(p),
@@ -219,6 +221,107 @@ OPTIONS:
     Ok(())
 }
 
+fn run_lite(p: &mut lexopt::Parser) -> anyhow::Result<()> {
+    const USAGE: &'static str = "\
+Executes a search for full matches using the top-level regex-lite engine.
+
+USAGE:
+    regex-cli find capture lite [-p <pattern> ...] <haystack-path>
+    regex-cli find capture lite [-p <pattern> ...] -y <haystack>
+
+TIP:
+    use -h for short docs and --help for long docs
+
+OPTIONS:
+%options%
+";
+
+    let mut common = args::common::Config::default();
+    let mut patterns = args::patterns::Config::only_flags();
+    let mut haystack = args::haystack::Config::default();
+    let mut syntax = args::syntax::Config::default();
+    let mut lite = args::lite::Config::default();
+    let mut find = super::Config::default();
+    args::configure(
+        p,
+        USAGE,
+        &mut [
+            &mut common,
+            &mut patterns,
+            &mut haystack,
+            &mut syntax,
+            &mut lite,
+            &mut find,
+        ],
+    )?;
+
+    let pats = patterns.get()?;
+    let syn = syntax.syntax()?;
+    let mut table = Table::empty();
+    let (re, time) = util::timeitr(|| lite.from_patterns(&syn, &pats))?;
+    table.add("build regex time", time);
+
+    // Check that the haystack is valid UTF-8 since regex-lite doesn't support
+    // searching arbitrary byte sequences. (At time of writing.)
+    haystack.get()?.to_str()?;
+
+    // The top-level API doesn't support regex-automata's more granular Input
+    // abstraction.
+    let input = args::input::Config::default();
+    // The top-level API also doesn't use 'Captures' from regex-automata
+    // directly, but we can map between them with some annoyance.
+    let group_info = GroupInfo::new([re.capture_names()])
+        .context("could not build capture group info")?;
+    let mut locs = re.capture_locations();
+    let search = |input: &Input<'_>, caps: &mut Captures| {
+        let haystack = input.haystack().to_str().unwrap();
+        caps.set_pattern(None);
+        if !re.captures_read_at(&mut locs, haystack, input.start()).is_some() {
+            return Ok(());
+        }
+        caps.set_pattern(Some(PatternID::ZERO));
+        for i in 0..locs.len() {
+            use regex_automata::util::primitives::NonMaxUsize;
+
+            let slot_start = i * 2;
+            let slot_end = slot_start + 1;
+            match locs.get(i) {
+                None => {
+                    caps.slots_mut()[slot_start] = None;
+                    caps.slots_mut()[slot_end] = None;
+                }
+                Some((start, end)) => {
+                    caps.slots_mut()[slot_start] = NonMaxUsize::new(start);
+                    caps.slots_mut()[slot_end] = NonMaxUsize::new(end);
+                }
+            }
+        }
+        Ok(())
+    };
+    if find.count {
+        run_counts(
+            &mut table,
+            &common,
+            &find,
+            &input,
+            &haystack,
+            &group_info,
+            search,
+        )?;
+    } else {
+        run_search(
+            &mut table,
+            &common,
+            &find,
+            &input,
+            &haystack,
+            &group_info,
+            search,
+        )?;
+    }
+    Ok(())
+}
+
 /// A function that takes in a bunch of configuration, runs the given search
 /// routine, and prints out a table of counts.
 fn run_counts(

regex-cli/cmd/find/match/mod.rs

@@ -26,6 +26,7 @@ ENGINES:
     backtrack  Search with the bounded backtracker regex engine.
     dense      Search with the dense DFA regex engine.
     hybrid     Search with the lazy DFA regex engine.
+    lite       Search with the regex-lite engine.
     meta       Search with the meta regex engine.
     onepass    Search with the one-pass DFA regex engine.
     pikevm     Search with the PikeVM regex engine.
@@ -37,6 +38,7 @@ ENGINES:
         "backtrack" => nfa::run_backtrack(p),
         "dense" => dfa::run_dense(p),
         "hybrid" => dfa::run_hybrid(p),
+        "lite" => run_lite(p),
         "meta" => run_meta(p),
         "onepass" => dfa::run_onepass(p),
         "pikevm" => nfa::run_pikevm(p),
@@ -164,6 +166,71 @@ OPTIONS:
     Ok(())
 }
 
+fn run_lite(p: &mut lexopt::Parser) -> anyhow::Result<()> {
+    const USAGE: &'static str = "\
+Executes a search for full matches using the top-level regex-lite engine.
+
+Note that since the regex-lite crate doesn't have an API for search arbitrary
+byte slices, the haystack must be valid UTF-8. If it isn't, this command will
+report an error.
+
+USAGE:
+    regex-cli find match lite [-p <pattern> ...] <haystack-path>
+    regex-cli find match lite [-p <pattern> ...] -y <haystack>
+
+TIP:
+    use -h for short docs and --help for long docs
+
+OPTIONS:
+%options%
+";
+
+    let mut common = args::common::Config::default();
+    let mut patterns = args::patterns::Config::only_flags();
+    let mut haystack = args::haystack::Config::default();
+    let mut syntax = args::syntax::Config::default();
+    let mut lite = args::lite::Config::default();
+    let mut find = super::Config::default();
+    args::configure(
+        p,
+        USAGE,
+        &mut [
+            &mut common,
+            &mut patterns,
+            &mut haystack,
+            &mut syntax,
+            &mut lite,
+            &mut find,
+        ],
+    )?;
+
+    let pats = patterns.get()?;
+    let syn = syntax.syntax()?;
+    let mut table = Table::empty();
+    let (re, time) = util::timeitr(|| lite.from_patterns(&syn, &pats))?;
+    table.add("build regex time", time);
+
+    // Check that the haystack is valid UTF-8 since regex-lite doesn't support
+    // searching arbitrary byte sequences. (At time of writing.)
+    haystack.get()?.to_str()?;
+
+    // The top-level regex-lite API doesn't support regex-automata's more
+    // granular Input abstraction.
+    let input = args::input::Config::default();
+    let search = |input: &Input<'_>| {
+        let haystack = input.haystack().to_str().unwrap();
+        Ok(re
+            .find_at(haystack, input.start())
+            .map(|m| Match::new(PatternID::ZERO, m.start()..m.end())))
+    };
+    if find.count {
+        run_counts(&mut table, &common, &find, &input, &haystack, 1, search)?;
+    } else {
+        run_search(&mut table, &common, &find, &input, &haystack, search)?;
+    }
+    Ok(())
+}
+
 /// A function that takes in a bunch of configuration, runs the given search
 /// routine, and prints out a table of counts.
 fn run_counts(

regex-lite/Cargo.toml

@@ -0,0 +1,36 @@
+[package]
+name = "regex-lite"
+version = "0.1.0"  #:version
+authors = ["The Rust Project Developers", "Andrew Gallant <[email protected]>"]
+license = "MIT OR Apache-2.0"
+repository = "https://github.com/rust-lang/regex/tree/master/regex-lite"
+documentation = "https://docs.rs/regex-lite"
+description = """
+A lightweight regex engine that optimizes for binary size and compilation time.
+"""
+workspace = ".."
+edition = "2021"
+rust-version = "1.60.0"
+autotests = false
+
+# Features are documented in the "Crate features" section of the crate docs:
+# https://docs.rs/regex-syntax/*/#crate-features
+[features]
+default = ["std"]
+std = []
+
+[dev-dependencies]
+anyhow = "1.0.69"
+regex-test = { path = "../regex-test", version = "0.1.0" }
+
+[[test]]
+path = "tests/lib.rs"
+name = "integration"
+
+[package.metadata.docs.rs]
+# We want to document all features.
+all-features = true
+# To test this locally, run:
+#
+#     RUSTDOCFLAGS="--cfg docsrs" cargo +nightly doc --all-features
+rustdoc-args = ["--cfg", "docsrs"]