Use BufferedOutputStream when writing the Zip file to improve performance (#1579)

* fix: use buffered writes for performance

When not using STORED entries use a BufferedOutputStream to avoid lots
of small writes to the file system.

Testing this with a 300mb jar build I see the total build time going
from 40s to 30s.

Note that it is not possible to do this with STORED entries as the
implementation requires a RandomAccessFile to update the CRC after
write.

* Cleanup

---------

Co-authored-by: Goooler <[email protected]>

Author: stuartwdouglas

src/docs/changes/README.md

@@ -3,6 +3,9 @@
 
 ## [Unreleased]
 
+**Changed**
+
+- Use `BufferedOutputStream` when writing the Zip file to improve performance. ([#1579](https://github.com/GradleUp/shadow/pull/1579))
 
 ## [v8.3.8] (2025-07-01)
 

src/main/groovy/com/github/jengelman/gradle/plugins/shadow/internal/DefaultZipCompressor.groovy

@@ -30,7 +30,10 @@ class DefaultZipCompressor implements ZipCompressor {
     @Override
     ZipOutputStream createArchiveOutputStream(File destination) {
         try {
-            ZipOutputStream zipOutputStream = new ZipOutputStream(destination)
+            ZipOutputStream zipOutputStream = entryCompressionMethod == ZipOutputStream.STORED ?
+                new ZipOutputStream(destination) :
+                // It is not possible to do this with STORED entries as the implementation requires a RandomAccessFile to update the CRC after write.
+                new ZipOutputStream(new BufferedOutputStream(new FileOutputStream(destination)))
             zipOutputStream.setUseZip64(zip64Mode)
             zipOutputStream.setMethod(entryCompressionMethod)
             return zipOutputStream