From: Yann Collet <cyan@fb.com>
Date: Thu, 25 Aug 2016 12:34:42 +0000 (+0200)
Subject: fixed : compression bug on very large files
X-Git-Tag: v1.0.0^2~34
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=96bdd87de4e40ae3fa921afe98a42f0184cb89fe;p=thirdparty%2Fzstd.git

fixed : compression bug on very large files
---

diff --git a/lib/compress/zstd_compress.c b/lib/compress/zstd_compress.c
index e0ae91bf8..0a2fb9afa 100644
--- a/lib/compress/zstd_compress.c
+++ b/lib/compress/zstd_compress.c
@@ -2274,7 +2274,7 @@ static size_t ZSTD_compress_generic (ZSTD_CCtx* cctx,
         if (cctx->lowLimit > (1<<30)) {
             U32 const btplus = (cctx->params.cParams.strategy == ZSTD_btlazy2) | (cctx->params.cParams.strategy == ZSTD_btopt);
             U32 const chainMask = (1 << (cctx->params.cParams.chainLog - btplus)) - 1;
-            U32 const newLowLimit = cctx->lowLimit & chainMask;   /* preserve position % chainSize */
+            U32 const newLowLimit = (cctx->lowLimit & chainMask) + (chainMask+1);   /* preserve position % chainSize, ensure current-repcode doesn't underflow */
             U32 const correction = cctx->lowLimit - newLowLimit;
             ZSTD_reduceIndex(cctx, correction);
             cctx->base += correction;