Create multi-part streams lazily

1 files changed, 7 insertions, 4 deletions

diff --git a/hosted-api/src/main/java/ai/vespa/hosted/api/MultiPartStreamer.java b/hosted-api/src/main/java/ai/vespa/hosted/api/MultiPartStreamer.java
index f1cbc027e17..c47fc60e58b 100644
--- a/hosted-api/src/main/java/ai/vespa/hosted/api/MultiPartStreamer.java
+++ b/hosted-api/src/main/java/ai/vespa/hosted/api/MultiPartStreamer.java
@@ -15,6 +15,7 @@ import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.Collections;
+import java.util.Enumeration;
 import java.util.List;
 import java.util.UUID;
 import java.util.function.Supplier;
@@ -89,10 +90,12 @@ public class MultiPartStreamer {
 
     /** Returns an input stream which is an aggregate of all current parts in this, plus an end marker. */
     public InputStream data() {
-        InputStream aggregate = new SequenceInputStream(Collections.enumeration(Stream.concat(streams.stream().map(Supplier::get),
-                                                                                              Stream.of(end()))
-                                                                                      .collect(Collectors.toList())));
-
+        InputStream aggregate = new SequenceInputStream(new Enumeration<>() {
+            final int j = streams.size();
+            int i = -1;
+            @Override public boolean hasMoreElements() { return i < j; }
+            @Override public InputStream nextElement() { return ++i < j ? streams.get(i).get() : end(); }
+        });
         try {
             if (aggregate.skip(2) != 2)// This should never happen, as the first stream is a ByteArrayInputStream.
                 throw new IllegalStateException("Failed skipping extraneous bytes.");