liuzqt commented on code in PR #38064:
URL: https://github.com/apache/spark/pull/38064#discussion_r993750676
##########
core/src/main/scala/org/apache/spark/util/io/ChunkedByteBuffer.scala:
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@@ -207,6 +273,41 @@ private[spark] object ChunkedByteBuffer {
}
out.toChunkedByteBuffer
}
+
+ /**
+ * util function writing ChunkedByteBuffer to destination with zero copy if
possible(when
+ * ChunkedByteBuffer is backed by bytes array)
+ * @param src ChunkedByteBuffer as src
+ * @param write write function writing data to destination, following the
semantic of
+ * java.io.outputStream.write(buffer Array[Byte], off Int, len
Int)
+ */
+ private def writeBufferToDest(
+ src: ChunkedByteBuffer,
+ write: (Array[Byte], Int, Int) => Unit): Unit = {
+ var buffer: Array[Byte] = null
+ val bufferLen = 1024 * 1024
+
+ src.chunks.foreach { chunk => {
+ if (chunk.hasArray) {
+ // zero copy if the bytebuffer is backed by bytes array
+ write(chunk.array(), chunk.arrayOffset(), chunk.limit())
+ } else {
+ // fallback to copy approach
+ if (buffer == null) {
+ buffer = new Array[Byte](bufferLen)
+ }
+ val originalPos = chunk.position()
+ chunk.rewind()
+ var bytesToRead = Math.min(chunk.remaining(), bufferLen)
+ while (bytesToRead > 0) {
+ chunk.get(buffer, 0, bytesToRead)
+ write(buffer, 0, bytesToRead)
+ bytesToRead = Math.min(chunk.remaining(), bufferLen)
+ }
+ chunk.position(originalPos)
+ }
+ }}
Review Comment:
this method (`writeToDest`) was removed together with `writeToStream` since
we don't have write-to-stream use case. Originally this method is introduced to
extract common logic in writing to `ObjectOutput` and `OutputStream`, but as we
don't have `OutputStream` usecase anymore, so this method can be removed. I put
the implementation back to `writeExternal` instead.
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