fuzz: use the bufrng crate instead of a local version

crates/fuzz-utils/src/lib.rs

@@ -425,54 +425,6 @@ pub fn print_err(e: &failure::Error) {
     }
 }
 
-/// An "RNG" implementation that just cycles through a given buffer.
-///
-/// This is useful for translating raw fuzzer input data from libFuzzer or AFL
-/// into an RNG that we can use to generate structured Wasm. Ultimately, this
-/// lets us combine the benefits of coverage-guided fuzzing with "structured"
-/// fuzzing (a la quickcheck::Arbitrary or whatever).
-pub struct BufRng<'a> {
-    iter: std::iter::Cycle<std::slice::Iter<'a, u8>>,
-}
-
-impl BufRng<'_> {
-    /// Construct a new `BufRng` that cycles over the given `data` buffer.
-    pub fn new(data: &[u8]) -> BufRng {
-        assert!(!data.is_empty());
-        BufRng {
-            iter: data.iter().cycle(),
-        }
-    }
-}
-
-// NB: all `RngCore` get a blanket `Rng` implementation.
-impl rand::RngCore for BufRng<'_> {
-    fn next_u32(&mut self) -> u32 {
-        let a = *self.iter.next().unwrap() as u32;
-        let b = *self.iter.next().unwrap() as u32;
-        let c = *self.iter.next().unwrap() as u32;
-        let d = *self.iter.next().unwrap() as u32;
-        (a << 24) & (b << 16) & (c << 8) & d
-    }
-
-    fn next_u64(&mut self) -> u64 {
-        let a = self.next_u32() as u64;
-        let b = self.next_u32() as u64;
-        (a << 32) & b
-    }
-
-    fn fill_bytes(&mut self, dest: &mut [u8]) {
-        for d in dest.iter_mut() {
-            *d = self.gen();
-        }
-    }
-
-    fn try_fill_bytes(&mut self, dest: &mut [u8]) -> std::result::Result<(), rand::Error> {
-        self.fill_bytes(dest);
-        Ok(())
-    }
-}
-
 #[cfg(test)]
 mod tests {
     use super::*;

fuzz/Cargo.toml

@@ -8,6 +8,9 @@ edition = "2018"
 [package.metadata]
 cargo-fuzz = true
 
+[dependencies]
+bufrng = "1.0.1"
+
 [dependencies.walrus]
 path = ".."
 

fuzz/fuzz_targets/wasm-opt-ttf.rs

@@ -3,7 +3,8 @@
 #[macro_use]
 extern crate libfuzzer_sys;
 
-use walrus_fuzz_utils::{BufRng, Config, WasmOptTtf};
+use bufrng::BufRng;
+use walrus_fuzz_utils::{Config, WasmOptTtf};
 
 fuzz_target!(|data: &[u8]| {
     let data = if data.is_empty() { &[0] } else { data };

fuzz/fuzz_targets/watgen.rs

@@ -3,7 +3,8 @@
 #[macro_use]
 extern crate libfuzzer_sys;
 
-use walrus_fuzz_utils::{BufRng, Config, WatGen};
+use bufrng::BufRng;
+use walrus_fuzz_utils::{Config, WatGen};
 
 fuzz_target!(|data: &[u8]| {
     let data = if data.is_empty() { &[0] } else { data };