Fix reading POW for edge bits 59 and higher #3069

hashmap · 2019-10-01T12:13:50Z

It requires reading more than 8 bytes

core/src/pow/types.rs

tromp · 2019-10-01T22:07:02Z

core/src/pow/types.rs

@@ -391,21 +391,39 @@ impl Proof {
 	}
 }

-#[inline(always)]
+fn extract_bits(bits: &Vec<u8>, bit_start: usize, bit_count: usize, read_from: usize) -> u64 {
+	let mut buf: [u8; 8] = [0; 8];


Is it possible in rust to directly assign

let bits64 = u64::from_le_bytes(&bits[read_from..read_from + 8]);

?
if so, that would be much preferable over the extra buffer and copying....

Other than that, this PR looks fine to me.

Array and slice are different types in Rust, so we can't directly use bits in from_le_bytes

and there's no function or method we can call on the slice to convert to array?

btw, remaining comments are just about aesthetics (can always be reconsidered later) and should not hold up this PR...

tromp · 2019-10-01T22:19:14Z

core/src/pow/types.rs

+		let mut v = Vec::with_capacity(42);
+		for _ in 0..42 {
+			v.push(rng.gen_range(
+				u64::pow(2, bits - 1),


btw, isn't it easier to write 1 << (bits - 1) than u64::pow(2, bits - 1) ?

I think it's easier to read u64::pow(2, bits - 1), so personally prefer it iff there's no performance hit.

Fix reading POW for edge bits 59 and higher

2c3128b

It requires reading more than 8 bytes

hashmap requested a review from tromp October 1, 2019 12:13