From c661c374e8df43365738daa09f4390d61bc57f08 Mon Sep 17 00:00:00 2001
From: Mark Adler <madler@alumni.caltech.edu>
Date: Sun, 24 Mar 2013 22:12:31 -0700
Subject: [PATCH] Do not return Z_BUF_ERROR if deflateParam() has nothing to
 write.

If the compressed data was already at a block boundary, then
deflateParam() would report Z_BUF_ERROR, because there was nothing
to write.  With this patch, Z_OK is returned in that case.
---
 deflate.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/deflate.c b/deflate.c
index 4aa5afb9..a942e252 100644
--- a/deflate.c
+++ b/deflate.c
@@ -513,6 +513,8 @@ int ZEXPORT deflateParams(strm, level, strategy)
         strm->total_in != 0) {
         /* Flush the last buffer: */
         err = deflate(strm, Z_BLOCK);
+        if (err == Z_BUF_ERROR && s->pending == 0)
+            err = Z_OK;
     }
     if (s->level != level) {
         s->level = level;