liuzqt commented on code in PR #38064:
URL: https://github.com/apache/spark/pull/38064#discussion_r991517511
##########
core/src/main/scala/org/apache/spark/util/io/ChunkedByteBuffer.scala:
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@@ -84,6 +91,104 @@ private[spark] class ChunkedByteBuffer(var chunks:
Array[ByteBuffer]) {
}
}
+ /**
+ * write to stream with zero copy if possible
+ */
+ def writeToStream(out: OutputStream): Unit = {
+ var buffer: Array[Byte] = null
+ val bufferLen = 1024 * 1024;
+ chunks.foreach(chunk => {
+ if (chunk.hasArray) {
+ // zero copy if the bytebuffer is backed by array
+ out.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)
+ out.write(buffer, 0, bytesToRead)
+ bytesToRead = Math.min(chunk.remaining(), bufferLen)
+ }
+ chunk.position(originalPos)
Review Comment:
Good idea! Extracted to `writeBufferToDest` helper function in companion
object.
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