Merge pull request #127 from EchoAlice/log2

Replaces `log_2` logic with `checked_ilog2`

.github/workflows/ci.yml

@@ -64,7 +64,7 @@ jobs:
   coverage:
     runs-on: ubuntu-latest
     container:
-      image: xd009642/tarpaulin:develop-nightly
+      image: xd009642/tarpaulin:latest
       options: --security-opt seccomp=unconfined
     steps:
       - name: Checkout sources

ssz-rs/src/lib.rs

@@ -60,7 +60,7 @@ mod lib {
         pub use std::*;
     }
 
-    pub use self::core::{any, cmp, fmt, iter, mem, slice};
+    pub use self::core::{any, cmp, fmt, iter, slice};
 
     pub use self::{
         cmp::Ordering,

ssz-rs/src/merkleization/multiproofs/generalized_index.rs

@@ -1,20 +1,9 @@
-use crate::{lib::mem, merkleization::MerkleizationError as Error};
-
-const BITS_PER_BYTE: usize = crate::BITS_PER_BYTE as usize;
-
-// From: https://users.rust-lang.org/t/logarithm-of-integers/8506/5
-const fn num_bits<T>() -> usize {
-    mem::size_of::<T>() * BITS_PER_BYTE
-}
+use crate::merkleization::MerkleizationError as Error;
 
 // Return base 2 logarithm of `x`.
 // `None` is returned if `x` is `0` as this logarithm is undefined.
 fn log_2(x: usize) -> Option<u32> {
-    if x == 0 {
-        None
-    } else {
-        Some(num_bits::<usize>() as u32 - x.leading_zeros() - 1)
-    }
+    x.checked_ilog2()
 }
 
 pub fn get_power_of_two_ceil(x: usize) -> usize {