From: W. Felix Handte <w@felixhandte.com>
Date: Wed, 8 Aug 2018 00:05:05 +0000 (-0700)
Subject: Fix CDict Attachment to Handle CDicts with Non-Zero Starts
X-Git-Tag: v0.0.29~51^2^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2ca7c69167e17006f867ab550408b6e0487a81e7;p=thirdparty%2Fzstd.git

Fix CDict Attachment to Handle CDicts with Non-Zero Starts

CDicts were previously guaranteed to be generated with `lowLimit=dictLimit=0`.
This is no longer true, and so the old length and index calculations are no
longer valid. This diff fixes them to handle non-zero start indices in CDicts.
---

diff --git a/lib/compress/zstd_compress.c b/lib/compress/zstd_compress.c
index 3ebfd019f..ed3aab871 100644
--- a/lib/compress/zstd_compress.c
+++ b/lib/compress/zstd_compress.c
@@ -1284,8 +1284,9 @@ static size_t ZSTD_resetCCtx_usingCDict(ZSTD_CCtx* cctx,
     }
 
     if (attachDict) {
-        const U32 cdictLen = (U32)( cdict->matchState.window.nextSrc
+        const U32 cdictEnd = (U32)( cdict->matchState.window.nextSrc
                                   - cdict->matchState.window.base);
+        const U32 cdictLen = cdictEnd - cdict->matchState.window.dictLimit;
         if (cdictLen == 0) {
             /* don't even attach dictionaries with no contents */
             DEBUGLOG(4, "skipping attaching empty dictionary");
@@ -1295,9 +1296,9 @@ static size_t ZSTD_resetCCtx_usingCDict(ZSTD_CCtx* cctx,
 
             /* prep working match state so dict matches never have negative indices
              * when they are translated to the working context's index space. */
-            if (cctx->blockState.matchState.window.dictLimit < cdictLen) {
+            if (cctx->blockState.matchState.window.dictLimit < cdictEnd) {
                 cctx->blockState.matchState.window.nextSrc =
-                    cctx->blockState.matchState.window.base + cdictLen;
+                    cctx->blockState.matchState.window.base + cdictEnd;
                 ZSTD_window_clear(&cctx->blockState.matchState.window);
             }
             cctx->blockState.matchState.loadedDictEnd = cctx->blockState.matchState.window.dictLimit;