Optimise conversion from Blob to Stream (#1609)

* Optimise conversion from Blob to Stream Motivated by http4s/http4s#7539 * Updated changelog
disneystreaming · Oct 14, 2024 · ec140e5 · ec140e5
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -5,6 +5,10 @@ When adding entries, please treat them as if they could end up in a release any
 
 Thank you!
 
+# 0.18.26
+
+* Optimises the conversion of empty smithy4s.Blob to fs2.Stream, to avoid performance degradation in Ember (see [#1609](https://github.com/disneystreaming/smithy4s/pull/1609))
+
 # 0.18.25
 
 * Add A flag to allow for numerics to be decoded from JSON strings (in smithy4s-json).

diff --git a/modules/http4s-kernel/src/smithy4s/http4s/kernel/package.scala b/modules/http4s-kernel/src/smithy4s/http4s/kernel/package.scala
@@ -204,6 +204,8 @@ package object kernel {
 
   private def toStream[F[_]](
       blob: Blob
-  ): Stream[F, Byte] = Stream.chunk(Chunk.array(blob.toArray))
+  ): Stream[F, Byte] =
+    // Optimisation motivated by https://github.com/http4s/http4s/issues/7539
+    if (blob.isEmpty) Stream.empty else Stream.chunk(Chunk.array(blob.toArray))
 
 }