Add log_iter utility macro

This is a useful primitive to have that formats the contents of the
iterator as a comma-separated list.

diff --git a/lightning/src/util/logger.rs b/lightning/src/util/logger.rs
index aac83f42a3c2f82a5520fc380f4006ca345288e2..722a81f7ab665b15961363a1f064377718e36dd3 100644 (file)
--- a/lightning/src/util/logger.rs
+++ b/lightning/src/util/logger.rs
@@ -169,6 +169,29 @@ impl<'a> core::fmt::Display for DebugBytes<'a> {
        }
 }
 
+/// Wrapper for logging `Iterator`s.
+///
+/// This is not exported to bindings users as fmt can't be used in C
+#[doc(hidden)]
+pub struct DebugIter<T: fmt::Display, I: core::iter::Iterator<Item = T> + Clone>(pub core::cell::RefCell<I>);
+impl<T: fmt::Display, I: core::iter::Iterator<Item = T> + Clone> fmt::Display for DebugIter<T, I> {
+       fn fmt(&self, f: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+               use core::ops::DerefMut;
+               write!(f, "[")?;
+               let iter_ref = self.0.clone();
+               let mut iter = iter_ref.borrow_mut();
+               for item in iter.deref_mut() {
+                       write!(f, "{}", item)?;
+                       break;
+               }
+               for item in iter.deref_mut() {
+                       write!(f, ", {}", item)?;
+               }
+               write!(f, "]")?;
+               Ok(())
+       }
+}
+
 #[cfg(test)]
 mod tests {
        use crate::util::logger::{Logger, Level};

diff --git a/lightning/src/util/macro_logger.rs b/lightning/src/util/macro_logger.rs
index 8742e8e84d0bf27670fb0cb71af3c372e089b9e3..4703bcdb32a2a00719f4d7a5eb1edd37aa2d75ec 100644 (file)
--- a/lightning/src/util/macro_logger.rs
+++ b/lightning/src/util/macro_logger.rs
@@ -17,6 +17,12 @@ use crate::routing::router::Route;
 use crate::ln::chan_utils::HTLCClaim;
 use crate::util::logger::DebugBytes;
 
+macro_rules! log_iter {
+       ($obj: expr) => {
+               $crate::util::logger::DebugIter(core::cell::RefCell::new($obj))
+       }
+}
+
 /// Logs a pubkey in hex format.
 #[macro_export]
 macro_rules! log_pubkey {