From 931b80f96f0314c43ac3b06085b30b39eebd3ba9 Mon Sep 17 00:00:00 2001
From: "Tobin C. Harding" <me@tobin.cc>
Date: Tue, 23 Jan 2024 16:00:04 +1100
Subject: [PATCH 1/2] Add CheckedHrpstring::fe32_iter function

Add a function that returns an iterator that yields field elements from
the data part of the parsed input bech32 string.
---
 src/primitives/decode.rs | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/src/primitives/decode.rs b/src/primitives/decode.rs
index 89a7edb93..f7a8be260 100644
--- a/src/primitives/decode.rs
+++ b/src/primitives/decode.rs
@@ -373,6 +373,16 @@ impl<'s> CheckedHrpstring<'s> {
     #[inline]
     pub fn data_part_ascii_no_checksum(&self) -> &[u8] { self.ascii }
 
+    /// Returns an iterator that yields the data part of the parsed bech32 encoded string as [`Fe32`]s.
+    ///
+    /// Converts the ASCII bytes representing field elements to the respective field elements.
+    #[inline]
+    pub fn fe32_iter<I: Iterator<Item = u8>>(
+        &self,
+    ) -> AsciiToFe32Iter<iter::Copied<slice::Iter<'s, u8>>> {
+        AsciiToFe32Iter { iter: self.ascii.iter().copied() }
+    }
+
     /// Returns an iterator that yields the data part of the parsed bech32 encoded string.
     ///
     /// Converts the ASCII bytes representing field elements to the respective field elements, then
@@ -658,14 +668,14 @@ impl<'s> Iterator for Fe32Iter<'s> {
     fn size_hint(&self) -> (usize, Option<usize>) { self.iter.size_hint() }
 }
 
-/// Helper iterator adaptor that maps an iterator of valid bech32 character ASCII bytes to an
+/// Iterator adaptor that maps an iterator of valid bech32 character ASCII bytes to an
 /// iterator of field elements.
 ///
 /// # Panics
 ///
 /// If any `u8` in the input iterator is out of range for an [`Fe32`]. Should only be used on data
 /// that has already been checked for validity (eg, by using `check_characters`).
-struct AsciiToFe32Iter<I: Iterator<Item = u8>> {
+pub struct AsciiToFe32Iter<I: Iterator<Item = u8>> {
     iter: I,
 }
 

From 319d9e335b1dcb4f783a455b3f532e917ca5526c Mon Sep 17 00:00:00 2001
From: "Tobin C. Harding" <me@tobin.cc>
Date: Tue, 23 Jan 2024 16:27:38 +1100
Subject: [PATCH 2/2] Remove generics from AsciiToFe32Iter

The `AsciiToFe32Iter` always iterates over the input string, we can just
use the lifetime from the string and a `iter::Copied<slice::Iter<'s,
u8>` iterator.
---
 src/primitives/decode.rs | 22 +++++++---------------
 1 file changed, 7 insertions(+), 15 deletions(-)

diff --git a/src/primitives/decode.rs b/src/primitives/decode.rs
index f7a8be260..04e3470a9 100644
--- a/src/primitives/decode.rs
+++ b/src/primitives/decode.rs
@@ -377,9 +377,7 @@ impl<'s> CheckedHrpstring<'s> {
     ///
     /// Converts the ASCII bytes representing field elements to the respective field elements.
     #[inline]
-    pub fn fe32_iter<I: Iterator<Item = u8>>(
-        &self,
-    ) -> AsciiToFe32Iter<iter::Copied<slice::Iter<'s, u8>>> {
+    pub fn fe32_iter<I: Iterator<Item = u8>>(&self) -> AsciiToFe32Iter {
         AsciiToFe32Iter { iter: self.ascii.iter().copied() }
     }
 
@@ -639,7 +637,7 @@ fn check_characters(s: &str) -> Result<usize, CharError> {
 
 /// An iterator over a parsed HRP string data as bytes.
 pub struct ByteIter<'s> {
-    iter: FesToBytes<AsciiToFe32Iter<iter::Copied<slice::Iter<'s, u8>>>>,
+    iter: FesToBytes<AsciiToFe32Iter<'s>>,
 }
 
 impl<'s> Iterator for ByteIter<'s> {
@@ -657,7 +655,7 @@ impl<'s> ExactSizeIterator for ByteIter<'s> {
 
 /// An iterator over a parsed HRP string data as field elements.
 pub struct Fe32Iter<'s> {
-    iter: AsciiToFe32Iter<iter::Copied<slice::Iter<'s, u8>>>,
+    iter: AsciiToFe32Iter<'s>,
 }
 
 impl<'s> Iterator for Fe32Iter<'s> {
@@ -675,14 +673,11 @@ impl<'s> Iterator for Fe32Iter<'s> {
 ///
 /// If any `u8` in the input iterator is out of range for an [`Fe32`]. Should only be used on data
 /// that has already been checked for validity (eg, by using `check_characters`).
-pub struct AsciiToFe32Iter<I: Iterator<Item = u8>> {
-    iter: I,
+pub struct AsciiToFe32Iter<'s> {
+    iter: iter::Copied<slice::Iter<'s, u8>>,
 }
 
-impl<I> Iterator for AsciiToFe32Iter<I>
-where
-    I: Iterator<Item = u8>,
-{
+impl<'s> Iterator for AsciiToFe32Iter<'s> {
     type Item = Fe32;
     #[inline]
     fn next(&mut self) -> Option<Fe32> { self.iter.next().map(Fe32::from_char_unchecked) }
@@ -693,10 +688,7 @@ where
     }
 }
 
-impl<I> ExactSizeIterator for AsciiToFe32Iter<I>
-where
-    I: Iterator<Item = u8> + ExactSizeIterator,
-{
+impl<'s> ExactSizeIterator for AsciiToFe32Iter<'s> {
     #[inline]
     fn len(&self) -> usize { self.iter.len() }
 }