feat: add todo

src/bitcoin/block.cairo

@@ -31,7 +31,7 @@ pub struct BlockHeader {
 /// In Cairo, the default encoding is big-endian, so this struct allows
 /// creation of a BlockHeader from human-readable values.
 /// Note: The Digest fields are already in little-endian format.
-
+// todo: BlockHeader with HumanReadable constructor and default one?
 #[derive(Drop, Copy, Debug, PartialEq, Default, Serde)]
 pub struct HumanReadableBlockHeader {
     pub version: u32,
@@ -42,6 +42,7 @@ pub struct HumanReadableBlockHeader {
     pub nonce: u32,
 }
 
+// todo: Precompiled Block Header?
 impl IntoBlockHeader of Into<HumanReadableBlockHeader, BlockHeader> {
     fn into(self: HumanReadableBlockHeader) -> BlockHeader {
         BlockHeader {
@@ -50,6 +51,7 @@ impl IntoBlockHeader of Into<HumanReadableBlockHeader, BlockHeader> {
             merkle_root_hash: self.merkle_root_hash,
             time: u32_byte_reverse(self.time),
             // we want to keep bits in little endian to allow for pow computation
+            // todo: split mantissa and precompute reversed?
             bits: self.bits,
             nonce: u32_byte_reverse(self.nonce),
         }
@@ -90,6 +92,7 @@ pub impl PowVerificationImpl of PowVerificationTrait {
     }
 
     /// Computes the target threshold for the block.
+    /// todo: optimize for errors and maths
     fn compute_target_threshold(self: @BlockHeader) -> u256 {
         let (exponent, mantissa) = DivRem::div_rem(*self.bits, 0x1000000);
 

src/utils/numeric.cairo

@@ -5,6 +5,7 @@
 ///
 /// This function takes a 32-bit unsigned integer and reverses the order of its bytes.
 /// It is useful for converting between big-endian and little-endian formats.
+/// todo: optimize with split_bytes?
 pub fn u32_byte_reverse(word: u32) -> u32 {
     let byte0 = (word & 0x000000FF) * 0x1000000_u32;
     let byte1 = (word & 0x0000FF00) * 0x00000100_u32;