Some code cleanups

Author: ndr-ds

linera-views/src/common.rs

@@ -74,9 +74,8 @@ impl DeletionSet {
 pub(crate) fn get_upper_bound_option(key_prefix: &[u8]) -> Option<Vec<u8>> {
     let len = key_prefix.len();
     for i in (0..len).rev() {
-        let val = key_prefix[i];
-        if val < u8::MAX {
-            let mut upper_bound = key_prefix[0..i + 1].to_vec();
+        if key_prefix[i] < u8::MAX {
+            let mut upper_bound = key_prefix[0..=i].to_vec();
             upper_bound[i] += 1;
             return Some(upper_bound);
         }

linera-views/src/random.rs

@@ -1,70 +1,47 @@
 // Copyright (c) Zefchain Labs, Inc.
 // SPDX-License-Identifier: Apache-2.0
 
-use rand::{Rng, SeedableRng};
+use rand::{
+    rngs::{SmallRng, ThreadRng},
+    Rng, SeedableRng,
+};
 
 // The following seed is chosen to have equal numbers of 1s and 0s, as advised by
 // https://docs.rs/rand/latest/rand/rngs/struct.SmallRng.html
 // Specifically, it's "01" × 32 in binary
 const RNG_SEED: u64 = 6148914691236517205;
 
 /// A deterministic RNG.
-pub type DeterministicRng = rand::rngs::SmallRng;
+pub type DeterministicRng = SmallRng;
 
 /// A RNG that is non-deterministic if the platform supports it.
-pub struct NonDeterministicRng(
-    #[cfg(target_arch = "wasm32")] std::sync::MutexGuard<'static, DeterministicRng>,
-    #[cfg(not(target_arch = "wasm32"))] rand::rngs::ThreadRng,
-);
-
-impl NonDeterministicRng {
-    /// Access the internal RNG.
-    pub fn rng_mut(&mut self) -> &mut impl Rng {
-        #[cfg(target_arch = "wasm32")]
-        {
-            &mut *self.0
-        }
-        #[cfg(not(target_arch = "wasm32"))]
-        {
-            &mut self.0
-        }
-    }
-}
+#[cfg(not(target_arch = "wasm32"))]
+pub type NonDeterministicRng = ThreadRng;
+#[cfg(target_arch = "wasm32")]
+pub type NonDeterministicRng = SmallRng;
 
 /// Returns a deterministic RNG for testing.
 pub fn make_deterministic_rng() -> DeterministicRng {
-    rand::rngs::SmallRng::seed_from_u64(RNG_SEED)
+    SmallRng::seed_from_u64(RNG_SEED)
 }
 
 /// Returns a non-deterministic RNG where supported.
 pub fn make_nondeterministic_rng() -> NonDeterministicRng {
     #[cfg(target_arch = "wasm32")]
     {
-        use std::sync::{Mutex, OnceLock};
-
-        use rand::rngs::SmallRng;
-
-        static RNG: OnceLock<Mutex<SmallRng>> = OnceLock::new();
-        NonDeterministicRng(
-            RNG.get_or_init(|| Mutex::new(make_deterministic_rng()))
-                .lock()
-                .expect("failed to lock RNG mutex"),
-        )
+        make_deterministic_rng()
     }
-
     #[cfg(not(target_arch = "wasm32"))]
     {
-        NonDeterministicRng(rand::thread_rng())
+        rand::thread_rng()
     }
 }
 
 /// Get a random alphanumeric string that can be used for all tests.
 pub fn generate_random_alphanumeric_string(length: usize, charset: &[u8]) -> String {
     (0..length)
         .map(|_| {
-            let random_index = make_nondeterministic_rng()
-                .rng_mut()
-                .gen_range(0..charset.len());
+            let random_index = make_nondeterministic_rng().gen_range(0..charset.len());
             charset[random_index] as char
         })
         .collect()

linera-views/src/test_utils/mod.rs

@@ -25,7 +25,7 @@ use crate::{
 /// Returns a random key prefix used for tests
 pub fn get_random_key_prefix() -> Vec<u8> {
     let mut key_prefix = vec![0];
-    let value: usize = make_nondeterministic_rng().rng_mut().gen();
+    let value: usize = make_nondeterministic_rng().gen();
     bcs::serialize_into(&mut key_prefix, &value).unwrap();
     key_prefix
 }