Samrat002 commented on code in PR #28112:
URL: https://github.com/apache/flink/pull/28112#discussion_r3201406435


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flink-filesystems/flink-s3-fs-native/src/test/java/org/apache/flink/fs/s3native/NativeS3InputStreamTest.java:
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@@ -333,15 +468,116 @@ void skipToEofWithOpenStreamReleasesStream() throws 
Exception {
 
             assertThat(in.skip(DATA.length)).isEqualTo(DATA.length - 1);
             assertThat(in.getPos()).isEqualTo(DATA.length);
+            assertThat(first.wasAborted()).isFalse();
 
-            assertThat(first.wasAborted()).isTrue();
-            assertThat(first.wasClosed()).isTrue();
-            assertThat(first.wasAbortedBeforeClose()).isTrue();
+            assertThat(in.read()).isEqualTo(-1);
+        }
+    }
+
+    @Test
+    void skipZeroAndNegativeAreNoOps() throws Exception {
+        StubS3Client client = new StubS3Client(DATA);
+        try (NativeS3InputStream in = new NativeS3InputStream(client, BUCKET, 
KEY, DATA.length)) {
+            in.read();
+            assertThat(in.skip(0)).isZero();
+            assertThat(in.skip(-5)).isZero();
             assertThat(client.getObjectCalls()).isEqualTo(1);
+        }
+    }
+
+    // --- read + seek integration ---
+
+    @Test
+    void readAndSeekReturnCorrectData() throws Exception {
+        StubS3Client client = new StubS3Client(DATA);
+        try (NativeS3InputStream in = new NativeS3InputStream(client, BUCKET, 
KEY, DATA.length)) {
+            assertThat(in.read()).isEqualTo(0);
+            assertThat(in.getPos()).isEqualTo(1);
+            byte[] buf = new byte[10];
+            assertThat(in.read(buf, 0, 10)).isEqualTo(10);
+            assertThat(in.getPos()).isEqualTo(11);
+            for (int i = 0; i < 10; i++) {
+                assertThat(buf[i]).isEqualTo(DATA[i + 1]);
+            }
+            assertThat(in.available()).isEqualTo(DATA.length - 11);
+            in.seek(200);
+            assertThat(in.read()).isEqualTo(200);
+            assertThat(in.getPos()).isEqualTo(201);
+            in.seek(250);
+            byte[] tail = new byte[20];
+            assertThat(in.read(tail, 0, 20)).isEqualTo(6);
+            assertThat(in.getPos()).isEqualTo(256);
             assertThat(in.read()).isEqualTo(-1);
+            assertThat(in.read(new byte[1], 0, 1)).isEqualTo(-1);
+        }
+    }
+
+    // --- buffer-efficiency: skip stays in local buffer vs. underlying stream 
---
+
+    @Test
+    void seekWithinBuffer_afterSmallRead_doesNotTouchUnderlyingStream() throws 
Exception {
+        int smallBuffer = 32;
+        StubS3Client client = new StubS3Client(DATA);
+        try (NativeS3InputStream in =
+                new NativeS3InputStream(client, BUCKET, KEY, DATA.length, 
smallBuffer)) {
+            // single-byte read fills the local buffer (up to smallBuffer 
bytes buffered)
+            in.read();
+            TrackingInputStream underlying = client.lastStream();
+
+            // forward seek of 9 bytes — fits in the local buffer, no 
underlying access needed
+            in.seek(10);
+            in.read();
+
+            assertThat(client.getObjectCalls()).isEqualTo(1);
+            assertThat(underlying.bytesSkippedFromUnderlying()).isEqualTo(0);

Review Comment:
   Added 



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