Allocation optimizations, review comments

lightning-invoice/src/de.rs

@@ -89,7 +89,8 @@ impl FromBase32 for Bolt11InvoiceFeatures {
 		// Carry bits, 0, 1, 2, 3, or 4 bits
 		let mut carry_bits = 0;
 		let mut carry = 0u8;
-		let mut output = Vec::<u8>::new();
+		let expected_raw_length = (field_data.len() * 5 + 7) / 8;
+		let mut output = Vec::<u8>::with_capacity(expected_raw_length);
 
 		// Iterate over input in reverse
 		for curr_in in field_data.iter().rev() {
@@ -107,14 +108,21 @@ impl FromBase32 for Bolt11InvoiceFeatures {
 				carry_bits += 5;
 			}
 		}
+
 		// No more inputs, output remaining (if any)
 		if carry_bits > 0 {
 			output.push(carry);
 		}
+
+		// This is to double check the estimated length and
+		// satisfying mutation test on the capacity, which is mutatable
+		debug_assert_eq!(output.len(), expected_raw_length);
+
 		// Trim the highest feature bits
 		while !output.is_empty() && output[output.len() - 1] == 0 {
 			output.pop();
 		}
+
 		Ok(Bolt11InvoiceFeatures::from_le_bytes(output))
 	}
 }
@@ -364,7 +372,7 @@ impl FromStr for SignedRawBolt11Invoice {
 	fn from_str(s: &str) -> Result<Self, Self::Err> {
 		let parsed = CheckedHrpstring::new::<Bech32>(s)?;
 		let hrp = parsed.hrp();
-		// Access original non-packed 32 byte values (as Fe32s)
+		// Access original non-packed 32 byte values (as Fe32s) (iterator type is needed for API hack)
 		let data: Vec<_> = parsed.fe32_iter::<alloc::boxed::Box<dyn Iterator<Item = u8>>>().collect();
 
 		const SIGNATURE_LEN5: usize = 104; // 32-bit values, 65 bytes
@@ -470,7 +478,7 @@ impl FromBase32 for Bolt11InvoiceSignature {
 				"Bolt11InvoiceSignature::from_base32()".into(),
 			));
 		}
-		let recoverable_signature_bytes = Vec::<u8>::from_base32(signature)?;
+		let recoverable_signature_bytes = <[u8; 65]>::from_base32(signature)?;
 		let signature = &recoverable_signature_bytes[0..64];
 		let recovery_id = RecoveryId::from_i32(recoverable_signature_bytes[64] as i32)?;
 
@@ -582,7 +590,7 @@ impl FromBase32 for Sha256 {
 			// "A reader MUST skip over […] a p, [or] h […] field that does not have data_length 52 […]."
 			Err(Bolt11ParseError::Skip)
 		} else {
-			Ok(Sha256(sha256::Hash::from_slice(&Vec::<u8>::from_base32(field_data)?)
+			Ok(Sha256(sha256::Hash::from_slice(&<[u8; 32]>::from_base32(field_data)?)
 				.expect("length was checked before (52 u5 -> 32 u8)")))
 		}
 	}
@@ -608,7 +616,7 @@ impl FromBase32 for PayeePubKey {
 			// "A reader MUST skip over […] a n […] field that does not have data_length 53 […]."
 			Err(Bolt11ParseError::Skip)
 		} else {
-			let data_bytes = Vec::<u8>::from_base32(field_data)?;
+			let data_bytes = <[u8; 33]>::from_base32(field_data)?;
 			let pub_key = PublicKey::from_slice(&data_bytes)?;
 			Ok(pub_key.into())
 		}

lightning-invoice/src/lib.rs

@@ -1002,7 +1002,8 @@ macro_rules! find_all_extract {
 impl RawBolt11Invoice {
 	/// Hash the HRP (as bytes) and signatureless data part (as Fe32 iterator)
 	fn hash_from_parts<'s>(hrp_bytes: &[u8], data_without_signature: Box<dyn Iterator<Item = Fe32> + 's>) -> [u8; 32] {
-		use crate::de::FromBase32;
+		use crate::bech32::Fe32IterExt;
+		use bitcoin::hashes::HashEngine;
 
 		let mut data_part = data_without_signature.collect::<Vec<Fe32>>();
 
@@ -1018,12 +1019,17 @@ impl RawBolt11Invoice {
 			}
 		}
 
-		let mut preimage = Vec::<u8>::from(hrp_bytes);
-		preimage.extend_from_slice(&Vec::<u8>::from_base32(&data_part)
-			.expect("No padding error may occur due to appended zero above."));
+		// Hash bytes and data part sequentially
+		let mut engine = sha256::Hash::engine();
+		engine.input(hrp_bytes);
+		// Iterate over data
+		// Note: if it was not for padding, this could go on the supplied original iterator
+		//  (see https://github.com/rust-bitcoin/rust-bech32/issues/198)
+		data_part.into_iter().fes_to_bytes().for_each(|v| { engine.input(&[v])});
+		let raw_hash = sha256::Hash::from_engine(engine);
 
 		let mut hash: [u8; 32] = Default::default();
-		hash.copy_from_slice(&sha256::Hash::hash(&preimage)[..]);
+		hash.copy_from_slice(raw_hash.as_ref());
 		hash
 	}