[GitHub] [arrow] kiszk commented on a change in pull request #7507: ARROW-8797: [C++] Read RecordBatch in a different endian

[GitBox]

kiszk commented on a change in pull request #7507:
URL: https://github.com/apache/arrow/pull/7507#discussion_r521501051



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File path: cpp/src/arrow/ipc/reader.cc
##########
@@ -699,42 +726,45 @@ Status ReadDictionary(const Buffer& metadata, 
DictionaryMemo* dictionary_memo,
 
   // Look up the dictionary value type, which must have been added to the
   // DictionaryMemo already prior to invoking this function
-  ARROW_ASSIGN_OR_RAISE(auto value_type, 
dictionary_memo->GetDictionaryType(id));
+  ARROW_ASSIGN_OR_RAISE(auto value_type, 
context.dictionary_memo->GetDictionaryType(id));
 
   // Load the dictionary data from the dictionary batch
   ArrayLoader loader(batch_meta, 
internal::GetMetadataVersion(message->version()),
-                     options, file);
-  const auto dict_data = std::make_shared<ArrayData>();
+                     context.options, file);
+  auto dict_data = std::make_shared<ArrayData>();
   const Field dummy_field("", value_type);
   RETURN_NOT_OK(loader.Load(&dummy_field, dict_data.get()));
 
   if (compression != Compression::UNCOMPRESSED) {
     ArrayDataVector dict_fields{dict_data};
-    RETURN_NOT_OK(DecompressBuffers(compression, options, &dict_fields));
+    RETURN_NOT_OK(DecompressBuffers(compression, context.options, 
&dict_fields));
+  }
+
+  // swap endian in dict_data if necessary (swap_endian == true)
+  if (context.swap_endian) {
+    SwapEndianArrayData(dict_data);
   }
 
   if (dictionary_batch->isDelta()) {
-    if (kind != nullptr) {
-      *kind = DictionaryKind::Delta;
+    if (context.kind != nullptr) {
+      *context.kind = DictionaryKind::Delta;
     }
-    return dictionary_memo->AddDictionaryDelta(id, dict_data);
+    return context.dictionary_memo->AddDictionaryDelta(id, dict_data);
   }
   ARROW_ASSIGN_OR_RAISE(bool inserted,
-                        dictionary_memo->AddOrReplaceDictionary(id, 
dict_data));
-  if (kind != nullptr) {
-    *kind = inserted ? DictionaryKind::New : DictionaryKind::Replacement;
+                        context.dictionary_memo->AddOrReplaceDictionary(id, 
dict_data));
+  if (context.kind != nullptr) {
+    *context.kind = inserted ? DictionaryKind::New : 
DictionaryKind::Replacement;
   }

Review comment:
       I see.
   
   @kou Is it ok to exclude `param` from `IpcReadContext`?




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