From 5275aed2f80e6c69d1ba5bd6b6d7cf18b8200461 Mon Sep 17 00:00:00 2001
From: Craig Tiller <ctiller@google.com>
Date: Tue, 12 Dec 2023 08:07:57 +0000
Subject: [PATCH] optimize channel args to string

---
 src/core/lib/channel/channel_args.cc | 38 ++++++++++++++++++----------
 src/core/lib/channel/channel_args.h  | 10 ++++----
 2 files changed, 29 insertions(+), 19 deletions(-)

diff --git a/src/core/lib/channel/channel_args.cc b/src/core/lib/channel/channel_args.cc
index 95010e332f0..80ac7f7569c 100644
--- a/src/core/lib/channel/channel_args.cc
+++ b/src/core/lib/channel/channel_args.cc
@@ -280,25 +280,35 @@ absl::optional<bool> ChannelArgs::GetBool(absl::string_view name) const {
   }
 }
 
-std::string ChannelArgs::Value::ToString() const {
-  if (rep_.c_vtable() == &int_vtable_) {
-    return std::to_string(reinterpret_cast<intptr_t>(rep_.c_pointer()));
-  }
+absl::string_view ChannelArgs::Value::ToString(
+    std::list<std::string>& backing_strings) const {
   if (rep_.c_vtable() == &string_vtable_) {
-    return std::string(
-        static_cast<RefCountedString*>(rep_.c_pointer())->as_string_view());
+    return static_cast<RefCountedString*>(rep_.c_pointer())->as_string_view();
+  }
+  if (rep_.c_vtable() == &int_vtable_) {
+    backing_strings.emplace_back(
+        std::to_string(reinterpret_cast<intptr_t>(rep_.c_pointer())));
+    return backing_strings.back();
   }
-  return absl::StrFormat("%p", rep_.c_pointer());
+  backing_strings.emplace_back(absl::StrFormat("%p", rep_.c_pointer()));
+  return backing_strings.back();
 }
 
 std::string ChannelArgs::ToString() const {
-  std::vector<std::string> arg_strings;
-  args_.ForEach(
-      [&arg_strings](const RefCountedStringValue& key, const Value& value) {
-        arg_strings.push_back(
-            absl::StrCat(key.as_string_view(), "=", value.ToString()));
-      });
-  return absl::StrCat("{", absl::StrJoin(arg_strings, ", "), "}");
+  std::vector<absl::string_view> strings;
+  std::list<std::string> backing_strings;
+  strings.push_back("{");
+  bool first = true;
+  args_.ForEach([&strings, &first, &backing_strings](
+                    const RefCountedStringValue& key, const Value& value) {
+    if (!first) strings.push_back(", ");
+    first = false;
+    strings.push_back(key.as_string_view());
+    strings.push_back("=");
+    strings.push_back(value.ToString(backing_strings));
+  });
+  strings.push_back("}");
+  return absl::StrJoin(strings, "");
 }
 
 ChannelArgs ChannelArgs::UnionWith(ChannelArgs other) const {
diff --git a/src/core/lib/channel/channel_args.h b/src/core/lib/channel/channel_args.h
index 2c10d955127..ca8df06a286 100644
--- a/src/core/lib/channel/channel_args.h
+++ b/src/core/lib/channel/channel_args.h
@@ -345,7 +345,7 @@ class ChannelArgs {
       return &rep_;
     }
 
-    std::string ToString() const;
+    absl::string_view ToString(std::list<std::string>& backing) const;
 
     grpc_arg MakeCArg(const char* name) const;
 
@@ -391,8 +391,8 @@ class ChannelArgs {
 
   // Only used in union_with_test.cc, reference version of UnionWith for
   // differential fuzzing.
-  GRPC_MUST_USE_RESULT ChannelArgs
-  FuzzingReferenceUnionWith(ChannelArgs other) const;
+  GRPC_MUST_USE_RESULT ChannelArgs FuzzingReferenceUnionWith(
+      ChannelArgs other) const;
 
   const Value* Get(absl::string_view name) const;
   GRPC_MUST_USE_RESULT ChannelArgs Set(absl::string_view name,
@@ -466,8 +466,8 @@ class ChannelArgs {
   GRPC_MUST_USE_RESULT ChannelArgs Remove(absl::string_view name) const;
   bool Contains(absl::string_view name) const;
 
-  GRPC_MUST_USE_RESULT ChannelArgs
-  RemoveAllKeysWithPrefix(absl::string_view prefix) const;
+  GRPC_MUST_USE_RESULT ChannelArgs RemoveAllKeysWithPrefix(
+      absl::string_view prefix) const;
 
   template <typename T>
   bool ContainsObject() const {