From: Sen Huang <senhuang96@fb.com>
Date: Wed, 15 Sep 2021 16:51:42 +0000 (-0700)
Subject: Fix NCountWriteBound
X-Git-Tag: v1.5.1~1^2~103^2~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=a7aa2c5df6ced5f3c2019a825cfb08a619cf6851;p=thirdparty%2Fzstd.git

Fix NCountWriteBound
---

diff --git a/lib/compress/fse_compress.c b/lib/compress/fse_compress.c
index faca767c5..5547b4ac0 100644
--- a/lib/compress/fse_compress.c
+++ b/lib/compress/fse_compress.c
@@ -221,7 +221,11 @@ size_t FSE_buildCTable_wksp(FSE_CTable* ct,
 ****************************************************************/
 size_t FSE_NCountWriteBound(unsigned maxSymbolValue, unsigned tableLog)
 {
-    size_t const maxHeaderSize = (((maxSymbolValue+1) * tableLog) >> 3) + 3;
+    size_t const maxHeaderSize = (((maxSymbolValue+1) * tableLog
+                                   + 4 /* bitCount initialized at 4 */
+                                   + 2 /* first two symbols may use one additional bit each */) / 8)
+                                    + 1 /* round up to whole nb bytes */
+                                    + 2 /* additional two bytes for bitstream flush */;
     return maxSymbolValue ? maxHeaderSize : FSE_NCOUNTBOUND;  /* maxSymbolValue==0 ? use default */
 }