Function for iterating over Offer TLV records

Add a utility function for iterating over Offer TLV records contained in
any valid TLV stream bytes. Using a common function ensures that
experimental TLV records are included once they are supported.

Author: jkczyz

lightning/src/offers/offer.rs

@@ -90,7 +90,7 @@ use crate::ln::channelmanager::PaymentId;
 use crate::ln::features::OfferFeatures;
 use crate::ln::inbound_payment::{ExpandedKey, IV_LEN};
 use crate::ln::msgs::{DecodeError, MAX_VALUE_MSAT};
-use crate::offers::merkle::{TaggedHash, TlvStream};
+use crate::offers::merkle::{TaggedHash, TlvRecord, TlvStream};
 use crate::offers::nonce::Nonce;
 use crate::offers::parse::{Bech32Encode, Bolt12ParseError, Bolt12SemanticError, ParsedMessage};
 use crate::offers::signer::{Metadata, MetadataMaterial, self};
@@ -128,7 +128,7 @@ impl OfferId {
 	}
 
 	fn from_valid_invreq_tlv_stream(bytes: &[u8]) -> Self {
-		let tlv_stream = TlvStream::new(bytes).range(OFFER_TYPES);
+		let tlv_stream = Offer::tlv_stream_iter(bytes);
 		let tagged_hash = TaggedHash::from_tlv_stream(Self::ID_TAG, tlv_stream);
 		Self(tagged_hash.to_bytes())
 	}
@@ -687,6 +687,12 @@ impl Offer {
 		self.contents.expects_quantity()
 	}
 
+	pub(super) fn tlv_stream_iter<'a>(
+		bytes: &'a [u8]
+	) -> impl core::iter::Iterator<Item = TlvRecord<'a>> {
+		TlvStream::new(bytes).range(OFFER_TYPES)
+	}
+
 	#[cfg(async_payments)]
 	pub(super) fn verify<T: secp256k1::Signing>(
 		&self, nonce: Nonce, key: &ExpandedKey, secp_ctx: &Secp256k1<T>

lightning/src/offers/static_invoice.rs

@@ -367,12 +367,10 @@ impl StaticInvoice {
 	}
 
 	pub(crate) fn from_same_offer(&self, invreq: &InvoiceRequest) -> bool {
-		let invoice_offer_tlv_stream = TlvStream::new(&self.bytes)
-			.range(OFFER_TYPES)
-			.map(|tlv_record| tlv_record.record_bytes);
-		let invreq_offer_tlv_stream = TlvStream::new(invreq.bytes())
-			.range(OFFER_TYPES)
-			.map(|tlv_record| tlv_record.record_bytes);
+		let invoice_offer_tlv_stream =
+			Offer::tlv_stream_iter(&self.bytes).map(|tlv_record| tlv_record.record_bytes);
+		let invreq_offer_tlv_stream =
+			Offer::tlv_stream_iter(invreq.bytes()).map(|tlv_record| tlv_record.record_bytes);
 		invoice_offer_tlv_stream.eq(invreq_offer_tlv_stream)
 	}
 }