incorporate first suggestions for writing EOS in File

cpp/src/arrow/ipc/writer.cc

@@ -999,6 +999,9 @@ class StreamBookKeeper {
   int64_t position_;
 };
 
+// End of stream marker
+constexpr int32_t kEos = 0;
+
 /// A IpcPayloadWriter implementation that writes to a IPC stream
 /// (with an end-of-stream marker)
 class PayloadStreamWriter : public internal::IpcPayloadWriter,
@@ -1022,7 +1025,6 @@ class PayloadStreamWriter : public internal::IpcPayloadWriter,
 
   Status Close() override {
     // Write 0 EOS message
-    const int32_t kEos = 0;
     return Write(&kEos, sizeof(int32_t));
   }
 };
@@ -1076,10 +1078,8 @@ class PayloadFileWriter : public internal::IpcPayloadWriter, protected StreamBoo
   }
 
   Status Close() override {
-    // Close stream for compatibility with sequential readers
-    RETURN_NOT_OK(UpdatePosition());
-    int32_t end_of_stream_marker = 0;
-    RETURN_NOT_OK(Write(&end_of_stream_marker, sizeof(int32_t)));
+    // Write 0 EOS message for compatibility with sequential readers
+    RETURN_NOT_OK(Write(&kEos, sizeof(int32_t)));
 
     // Write file footer
     RETURN_NOT_OK(UpdatePosition());

java/vector/src/main/java/org/apache/arrow/vector/ipc/ArrowFileWriter.java

@@ -65,6 +65,7 @@ public class ArrowFileWriter extends ArrowWriter {
 
   @Override
   protected void endInternal(WriteChannel out) throws IOException {
+    out.writeIntLittleEndian(0); // Write an EOS identifier for sequential readers
     long footerStart = out.getCurrentPosition();
     out.write(new ArrowFooter(schema, dictionaryBlocks, recordBlocks), false);
     int footerLength = (int) (out.getCurrentPosition() - footerStart);

js/src/ipc/writer.ts

@@ -314,6 +314,7 @@ export class RecordBatchFileWriter<T extends { [key: string]: DataType } = any>
             this._recordBatchBlocks, this._dictionaryBlocks
         ));
         return this
+            ._writePadding(4) // eos bytes for sequential readers
             ._write(buffer) // Write the flatbuffer
             ._write(Int32Array.of(buffer.byteLength)) // then the footer size suffix
             ._writeMagic(); // then the magic suffix