From dfc02ad209bd5d8ec8339a92b44eadf27130f3a3 Mon Sep 17 00:00:00 2001
From: darkwater <dark@dark.red>
Date: Wed, 10 Sep 2025 16:23:43 +0200
Subject: [PATCH] Add support for defmt

---
 Cargo.toml |  1 +
 src/lib.rs | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 52 insertions(+)

diff --git a/Cargo.toml b/Cargo.toml
index d90e58f..78762b4 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -22,6 +22,7 @@ extract_if = []
 bytes = { version = "1", optional = true, default-features = false }
 serde = { version = "1", optional = true, default-features = false }
 malloc_size_of = { version = "0.1.1", optional = true, default-features = false }
+defmt = { version = "1", optional = true }
 
 [dev-dependencies]
 bincode = "1.0.1"
diff --git a/src/lib.rs b/src/lib.rs
index 42a60ef..86e2ae4 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -105,6 +105,7 @@ use serde::{
 use std::io;
 
 /// Error type for APIs with fallible heap allocation
+#[cfg_attr(feature = "defmt", derive(defmt::Format))]
 #[derive(Debug)]
 pub enum CollectionAllocErr {
     /// Overflow `usize::MAX` or other error during size computation
@@ -562,6 +563,18 @@ where
     }
 }
 
+#[cfg(all(feature = "extract_if", feature = "defmt"))]
+#[cfg_attr(docsrs, doc(cfg(feature = "defmt")))]
+impl<T, const N: usize, F> defmt::Format for ExtractIf<'_, T, N, F>
+where
+    F: FnMut(&mut T) -> bool,
+    T: defmt::Format,
+{
+    fn format(&self, fmt: defmt::Formatter) {
+        defmt::write!(fmt, "ExtractIf({:?})", self.vec.as_slice());
+    }
+}
+
 #[cfg(feature = "extract_if")]
 impl<T, F, const N: usize> Iterator for ExtractIf<'_, T, N, F>
 where
@@ -638,6 +651,17 @@ where
     }
 }
 
+#[cfg(feature = "defmt")]
+impl<'a, I, const N: usize> defmt::Format for Splice<'a, I, N>
+where
+    I: Iterator + 'a,
+    <I as Iterator>::Item: defmt::Format,
+{
+    fn format(&self, fmt: defmt::Formatter) {
+        defmt::write!(fmt, "Splice({:?})", self.drain);
+    }
+}
+
 impl<I: Iterator, const N: usize> Iterator for Splice<'_, I, N> {
     type Item = I::Item;
 
@@ -2851,6 +2875,33 @@ impl<T: Debug, const N: usize> Debug for Drain<'_, T, N> {
     }
 }
 
+#[cfg(feature = "defmt")]
+#[cfg_attr(docsrs, doc(cfg(feature = "defmt")))]
+impl<T: defmt::Format, const N: usize> defmt::Format for SmallVec<T, N> {
+    fn format(&self, fmt: defmt::Formatter) {
+        defmt::write!(fmt, "{=[?]}", self.as_slice());
+    }
+}
+
+#[cfg(feature = "defmt")]
+#[cfg_attr(docsrs, doc(cfg(feature = "defmt")))]
+impl<T: defmt::Format, const N: usize> defmt::Format for IntoIter<T, N> {
+    fn format(&self, fmt: defmt::Formatter) {
+        defmt::write!(fmt, "IntoIter({=[?]})", self.as_slice());
+    }
+}
+
+#[cfg(feature = "defmt")]
+#[cfg_attr(docsrs, doc(cfg(feature = "defmt")))]
+impl<T: defmt::Format, const N: usize> defmt::Format for Drain<'_, T, N>
+where
+    T: defmt::Format,
+{
+    fn format(&self, fmt: defmt::Formatter) {
+        defmt::write!(fmt, "Drain({=[?]})", self.iter.as_slice());
+    }
+}
+
 #[cfg(feature = "serde")]
 #[cfg_attr(docsrs, doc(cfg(feature = "serde")))]
 impl<T, const N: usize> Serialize for SmallVec<T, N>