fuzz: use structured fuzzer input

This makes a couple of the fuzzer targets a bit nicer by just asking for
structured data instead of trying to manifest it ourselves out of a
&[u8].

Closes #821

fuzz/Cargo.toml

@@ -9,7 +9,7 @@ edition = "2021"
 cargo-fuzz = true
 
 [dependencies]
-libfuzzer-sys = "0.4.1"
+libfuzzer-sys = { version = "0.4.1", features = ["arbitrary-derive"] }
 regex = { path = ".." }
 regex-automata = { path = "../regex-automata" }
 regex-lite = { path = "../regex-lite" }

fuzz/fuzz_targets/fuzz_regex_lite_match.rs

@@ -1,23 +1,60 @@
 #![no_main]
 
-use libfuzzer_sys::fuzz_target;
+use libfuzzer_sys::{arbitrary, fuzz_target};
 
-fuzz_target!(|data: &[u8]| {
-    let _ = run(data);
-});
+#[derive(arbitrary::Arbitrary)]
+struct FuzzCase<'a> {
+    pattern: &'a str,
+    haystack: &'a str,
+    case_insensitive: bool,
+    multi_line: bool,
+    crlf: bool,
+    dot_matches_new_line: bool,
+    swap_greed: bool,
+    ignore_whitespace: bool,
+}
+
+impl std::fmt::Debug for FuzzCase<'_> {
+    fn fmt(
+        &self,
+        fmt: &mut std::fmt::Formatter,
+    ) -> Result<(), std::fmt::Error> {
+        let FuzzCase {
+            pattern,
+            case_insensitive,
+            multi_line,
+            crlf,
+            dot_matches_new_line,
+            swap_greed,
+            ignore_whitespace,
+            haystack,
+        } = self;
 
-fn run(data: &[u8]) -> Option<()> {
-    if data.len() < 2 {
-        return None;
+        write!(
+            fmt,
+            r#"
+let Ok(re) = regex_lite::RegexBuilder::new({pattern:?})
+    .case_insensitive({case_insensitive:?})
+    .multi_line({multi_line:?})
+    .crlf({crlf:?})
+    .dot_matches_new_line({dot_matches_new_line:?})
+    .swap_greed({swap_greed:?})
+    .ignore_whitespace({ignore_whitespace:?})
+    .build() else {{ return }};
+re.is_match({haystack:?});
+        "#
+        )
     }
-    let mut split_at = usize::from(data[0]);
-    let data = std::str::from_utf8(&data[1..]).ok()?;
-    // Split data into a regex and haystack to search.
-    let len = usize::try_from(data.chars().count()).ok()?;
-    split_at = std::cmp::max(split_at, 1) % len;
-    let char_index = data.char_indices().nth(split_at)?.0;
-    let (pattern, input) = data.split_at(char_index);
-    let re = regex_lite::Regex::new(pattern).ok()?;
-    re.is_match(input);
-    Some(())
 }
+
+fuzz_target!(|case: FuzzCase| {
+    let Ok(re) = regex_lite::RegexBuilder::new(case.pattern)
+        .case_insensitive(case.case_insensitive)
+        .multi_line(case.multi_line)
+        .crlf(case.crlf)
+        .dot_matches_new_line(case.dot_matches_new_line)
+        .swap_greed(case.swap_greed)
+        .ignore_whitespace(case.ignore_whitespace)
+        .build() else { return };
+    re.is_match(case.haystack);
+});

fuzz/fuzz_targets/fuzz_regex_match.rs

@@ -1,23 +1,64 @@
 #![no_main]
 
-use libfuzzer_sys::fuzz_target;
+use libfuzzer_sys::{arbitrary, fuzz_target};
 
-fuzz_target!(|data: &[u8]| {
-    let _ = run(data);
-});
+#[derive(arbitrary::Arbitrary)]
+struct FuzzCase<'a> {
+    pattern: &'a str,
+    haystack: &'a str,
+    case_insensitive: bool,
+    multi_line: bool,
+    dot_matches_new_line: bool,
+    swap_greed: bool,
+    ignore_whitespace: bool,
+    unicode: bool,
+    octal: bool,
+}
+
+impl std::fmt::Debug for FuzzCase<'_> {
+    fn fmt(
+        &self,
+        fmt: &mut std::fmt::Formatter,
+    ) -> Result<(), std::fmt::Error> {
+        let FuzzCase {
+            pattern,
+            case_insensitive,
+            multi_line,
+            dot_matches_new_line,
+            swap_greed,
+            ignore_whitespace,
+            unicode,
+            octal,
+            haystack,
+        } = self;
 
-fn run(data: &[u8]) -> Option<()> {
-    if data.len() < 2 {
-        return None;
+        write!(
+            fmt,
+            r#"
+let Ok(re) = regex::RegexBuilder::new({pattern:?})
+    .case_insensitive({case_insensitive:?})
+    .multi_line({multi_line:?})
+    .dot_matches_new_line({dot_matches_new_line:?})
+    .swap_greed({swap_greed:?})
+    .ignore_whitespace({ignore_whitespace:?})
+    .unicode({unicode:?})
+    .octal({octal:?})
+    .build() else {{ return }};
+re.is_match({haystack:?});
+        "#
+        )
     }
-    let mut split_at = usize::from(data[0]);
-    let data = std::str::from_utf8(&data[1..]).ok()?;
-    // Split data into a regex and haystack to search.
-    let len = usize::try_from(data.chars().count()).ok()?;
-    split_at = std::cmp::max(split_at, 1) % len;
-    let char_index = data.char_indices().nth(split_at)?.0;
-    let (pattern, input) = data.split_at(char_index);
-    let re = regex::Regex::new(pattern).ok()?;
-    re.is_match(input);
-    Some(())
 }
+
+fuzz_target!(|case: FuzzCase| {
+    let Ok(re) = regex::RegexBuilder::new(case.pattern)
+        .case_insensitive(case.case_insensitive)
+        .multi_line(case.multi_line)
+        .dot_matches_new_line(case.dot_matches_new_line)
+        .swap_greed(case.swap_greed)
+        .ignore_whitespace(case.ignore_whitespace)
+        .unicode(case.unicode)
+        .octal(case.octal)
+        .build() else { return };
+    re.is_match(case.haystack);
+});