From 25b01e09e7b6a29b91148ca3f68c1551fb37903a Mon Sep 17 00:00:00 2001
From: alytantawyy <alytantawy@usf.edu>
Date: Fri, 12 Jun 2026 13:42:55 -0700
Subject: [PATCH] GH-50148: [C++] Add Content-Encoding support to S3 filesystem
 metadata

---
 cpp/src/arrow/filesystem/s3fs.cc      |  9 +++++++++
 cpp/src/arrow/filesystem/s3fs_test.cc | 10 ++++++----
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/cpp/src/arrow/filesystem/s3fs.cc b/cpp/src/arrow/filesystem/s3fs.cc
index 0c15f6f18444..de68c7196255 100644
--- a/cpp/src/arrow/filesystem/s3fs.cc
+++ b/cpp/src/arrow/filesystem/s3fs.cc
@@ -1301,6 +1301,7 @@ std::shared_ptr<const KeyValueMetadata> GetObjectMetadata(const ObjectResult& re
 
   md->Append("Content-Length", ToChars(result.GetContentLength()));
   push("Cache-Control", result.GetCacheControl());
+  push("Content-Encoding", result.GetContentEncoding());
   push("Content-Type", result.GetContentType());
   push("Content-Language", result.GetContentLanguage());
   push("ETag", result.GetETag());
@@ -1319,6 +1320,7 @@ struct ObjectMetadataSetter {
   static std::unordered_map<std::string, Setter> GetSetters() {
     return {{"ACL", CannedACLSetter()},
             {"Cache-Control", StringSetter(&ObjectRequest::SetCacheControl)},
+            {"Content-Encoding", ContentEncodingSetter()},
             {"Content-Type", ContentTypeSetter()},
             {"Content-Language", StringSetter(&ObjectRequest::SetContentLanguage)},
             {"Expires", DateTimeSetter(&ObjectRequest::SetExpires)}};
@@ -1359,6 +1361,13 @@ struct ObjectMetadataSetter {
     };
   }
 
+  static Setter ContentEncodingSetter() {
+    return [](const std::string& str, ObjectRequest* req) {
+      req->SetContentEncoding(str);
+      return Status::OK();
+    };
+  }
+
   static Result<S3Model::ObjectCannedACL> ParseACL(const std::string& v) {
     if (v.empty()) {
       return S3Model::ObjectCannedACL::NOT_SET;
diff --git a/cpp/src/arrow/filesystem/s3fs_test.cc b/cpp/src/arrow/filesystem/s3fs_test.cc
index 6be20603a8f3..7478baabebeb 100644
--- a/cpp/src/arrow/filesystem/s3fs_test.cc
+++ b/cpp/src/arrow/filesystem/s3fs_test.cc
@@ -1532,8 +1532,9 @@ TEST_F(TestS3FS, OpenOutputStreamMetadata) {
                           testing::IsSupersetOf(implicit_metadata->sorted_pairs()));
 
   // Create new file with explicit metadata
-  auto metadata = KeyValueMetadata::Make({"Content-Type", "Expires"},
-                                         {"x-arrow/test6", "2016-02-05T20:08:35Z"});
+  auto metadata = KeyValueMetadata::Make(
+      {"Content-Encoding", "Content-Type", "Expires"},
+      {"gzip", "x-arrow/test6", "2016-02-05T20:08:35Z"});
   AssertMetadataRoundtrip("bucket/mdfile1", metadata,
                           testing::IsSupersetOf(metadata->sorted_pairs()));
 
@@ -1543,8 +1544,9 @@ TEST_F(TestS3FS, OpenOutputStreamMetadata) {
   AssertMetadataRoundtrip("bucket/mdfile2", metadata, testing::_);
 
   // Create new file with default metadata
-  auto default_metadata = KeyValueMetadata::Make({"Content-Type", "Content-Language"},
-                                                 {"image/png", "fr_FR"});
+  auto default_metadata = KeyValueMetadata::Make(
+      {"Content-Encoding", "Content-Type", "Content-Language"},
+      {"br", "image/png", "fr_FR"});
   options_.default_metadata = default_metadata;
   MakeFileSystem();
   // (null, then empty metadata argument)