bp/Response: move code to resource_tag_append_etag_encoding()

src/bp/Response.cxx

@@ -128,7 +128,7 @@ GetEncodingCacheKey(AllocatorPtr alloc,
 		if (const auto etag = response_headers.GetSloppy(etag_header);
 		    etag.data() != nullptr)
 			return StringWithHash{
-				alloc.ConcatView(resource_tag, "|etag="sv, etag, "."sv, encoding),
+				resource_tag_append_etag_encoding(alloc, resource_tag, etag, encoding),
 			};
 
 	return StringWithHash{nullptr};

src/resource_tag.cxx

@@ -8,6 +8,16 @@
 #include "http/List.hxx"
 #include "AllocatorPtr.hxx"
 
+using std::string_view_literals::operator""sv;
+
+std::string_view
+resource_tag_append_etag_encoding(AllocatorPtr alloc, std::string_view tag,
+				  std::string_view etag,
+				  std::string_view encoding) noexcept
+{
+	return alloc.ConcatView(tag, "|etag="sv, etag, "."sv, encoding);
+}
+
 const char *
 resource_tag_append_etag(AllocatorPtr alloc, const char *tag,
 			 const StringMap &headers) noexcept

src/resource_tag.hxx

@@ -4,9 +4,20 @@
 
 #pragma once
 
+#include <string_view>
+
 class AllocatorPtr;
 class StringMap;
 
+/**
+ * A tag which addresses a resource in the filter cache.
+ */
+[[gnu::pure]]
+std::string_view
+resource_tag_append_etag_encoding(AllocatorPtr alloc, std::string_view tag,
+				  std::string_view etag,
+				  std::string_view encoding) noexcept;
+
 /**
  * A tag which addresses a resource in the filter cache.
  */