From: Mark Adler <madler@alumni.caltech.edu>
Date: Sat, 4 Apr 2026 01:16:25 +0000 (-0700)
Subject: Make deflateBound() more conservative and handle negative wrap.
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=3bea50d76a2f914cd27876684435dee435f79ee2;p=thirdparty%2Fzlib-ng.git

Make deflateBound() more conservative and handle negative wrap.

Use GZIP_WRAPLEN instead of 6 when parameters are unavailable, and
handle negative s->wrap values in the switch.

Upstream: https://github.com/madler/zlib/commit/a8c321be
---

diff --git a/deflate.c b/deflate.c
index 043c35fbf..347123806 100644
--- a/deflate.c
+++ b/deflate.c
@@ -698,13 +698,13 @@ unsigned long Z_EXPORT PREFIX(deflateBound)(PREFIX3(stream) *strm, unsigned long
     complen = sourceLen + ((sourceLen + 7) >> 3) + ((sourceLen + 63) >> 6) + 5;
     DEFLATE_BOUND_ADJUST_COMPLEN(strm, complen, sourceLen);  /* hook for IBM Z DFLTCC */
 
-    /* if can't get parameters, return conservative bound plus zlib wrapper */
+    /* if can't get parameters, return conservative bound plus a wrapper */
     if (deflateStateCheck(strm))
-        return complen + 6;
+        return complen + GZIP_WRAPLEN;
 
     /* compute wrapper length */
     s = strm->state;
-    switch (s->wrap) {
+    switch (ABS(s->wrap)) {
     case 0:                                 /* raw deflate */
         wraplen = 0;
         break;