smengcl commented on code in PR #4315:
URL: https://github.com/apache/ozone/pull/4315#discussion_r1129956985
##########
hadoop-hdds/rocks-native/src/main/java/org/apache/hadoop/hdds/utils/db/managed/PipeInputStream.java:
##########
@@ -0,0 +1,81 @@
+package org.apache.hadoop.hdds.utils.db.managed;
+
+import org.apache.hadoop.hdds.utils.NativeLibraryLoader;
+import org.apache.hadoop.hdds.utils.NativeLibraryNotLoadedException;
+import java.io.InputStream;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+import static
org.apache.hadoop.hdds.utils.NativeConstants.ROCKS_TOOLS_NATIVE_LIBRARY_NAME;
+
+/**
+ * JNI for reading data from pipe.
+ */
+public class PipeInputStream extends InputStream {
+
+ static {
+ NativeLibraryLoader.getInstance()
+ .loadLibrary(ROCKS_TOOLS_NATIVE_LIBRARY_NAME);
+ }
+ private byte[] byteBuffer;
+ private long nativeHandle;
+ private int numberOfBytesLeftToRead;
+ private int index = 0;
+ private int capacity;
+
+ private AtomicBoolean cleanup;
+
+ PipeInputStream(int capacity) throws NativeLibraryNotLoadedException {
+ if (!NativeLibraryLoader.getInstance()
+ .isLibraryLoaded(ROCKS_TOOLS_NATIVE_LIBRARY_NAME)) {
+ throw new NativeLibraryNotLoadedException(
+ ROCKS_TOOLS_NATIVE_LIBRARY_NAME);
+ }
+
+ this.byteBuffer = new byte[capacity];
+ this.numberOfBytesLeftToRead = 0;
+ this.capacity = capacity;
+ this.nativeHandle = newPipe();
+ this.cleanup = new AtomicBoolean(false);
+ }
+
+ long getNativeHandle() {
+ return nativeHandle;
+ }
+
+ @Override
+ public int read() {
+ if (numberOfBytesLeftToRead < 0) {
+ this.close();
+ return -1;
+ }
+ if (numberOfBytesLeftToRead == 0) {
+ numberOfBytesLeftToRead = readInternal(byteBuffer, capacity,
+ nativeHandle);
+ index = 0;
+ return read();
+ }
+ numberOfBytesLeftToRead--;
+ int ret = byteBuffer[index] & 0xFF;
+ index += 1;
+ return ret;
Review Comment:
Got it. I wonder if there a way to read from it more efficiently while
maintaining the correctness? `int` is at least 4 bytes but we are only
utilizing 1 byte.
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