From f1ebdd6a9c495a5db9a22aa80dd7d54ae7db42e9 Mon Sep 17 00:00:00 2001
From: Mark Adler <madler@alumni.caltech.edu>
Date: Wed, 28 Dec 2011 23:57:14 -0800
Subject: Permit stronger flushes after Z_BLOCK flushes.
The incorporation of the Z_BLOCK flush did not update the rejection
of lower ranked flushes immediately after higher ranked flushes with
no more input data. This prevented an empty Z_SYNC_FLUSH right after
a Z_BLOCK flush, which would be desired to bring the deflate stream
to a byte boundary conditionally on whether or not it was already at
a byte boundary. This patch re-ranks Z_BLOCK above Z_NO_FLUSH but
below Z_PARTIAL_FLUSH, allowing stronger empty flushes to follow a
Z_BLOCK flush.
---
deflate.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/deflate.c b/deflate.c
index f27febb..5d1d7bd 100644
--- a/deflate.c
+++ b/deflate.c
@@ -155,6 +155,9 @@ local const config configuration_table[10] = {
struct static_tree_desc_s {int dummy;}; /* for buggy compilers */
#endif
+/* rank Z_BLOCK between Z_NO_FLUSH and Z_PARTIAL_FLUSH */
+#define RANK(f) (((f) << 1) - ((f) > 4 ? 9 : 0))
+
/* ===========================================================================
* Update a hash value with the given input byte
* IN assertion: all calls to to UPDATE_HASH are made with consecutive
@@ -858,7 +861,7 @@ int ZEXPORT deflate (strm, flush)
* flushes. For repeated and useless calls with Z_FINISH, we keep
* returning Z_STREAM_END instead of Z_BUF_ERROR.
*/
- } else if (strm->avail_in == 0 && flush <= old_flush &&
+ } else if (strm->avail_in == 0 && RANK(flush) <= RANK(old_flush) &&
flush != Z_FINISH) {
ERR_RETURN(strm, Z_BUF_ERROR);
}
--
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