Refactor dictionary matchfinder index safety check (#4039)

diff --git a/lib/compress/zstd_compress_internal.h b/lib/compress/zstd_compress_internal.h
index e41d7b78ec6aaa5bd237667f4a9efcc81bf8a97c..f8ec1c82e8704b0b95e79beaaa3a47e3ecb28476 100644 (file)
--- a/lib/compress/zstd_compress_internal.h
+++ b/lib/compress/zstd_compress_internal.h
@@ -1315,6 +1315,13 @@ MEM_STATIC U32 ZSTD_getLowestPrefixIndex(const ZSTD_matchState_t* ms, U32 curr,
     return matchLowest;
 }
 
+/* index_safety_check:
+ * intentional underflow : ensure repIndex isn't overlapping dict + prefix
+ * @return 1 if values are not overlapping,
+ * 0 otherwise */
+MEM_STATIC int ZSTD_index_overlap_check(const U32 prefixLowestIndex, const U32 repIndex) {
+    return ((U32)((prefixLowestIndex-1)  - repIndex) >= 3);
+}
 
 
 /* debug functions */

diff --git a/lib/compress/zstd_double_fast.c b/lib/compress/zstd_double_fast.c
index a4e9c50d3bfeaf2cbe9cbdbb7e3e39a5af0fb5c4..1b5f64f20bb35f87f8fec94d72bb2910384298a2 100644 (file)
--- a/lib/compress/zstd_double_fast.c
+++ b/lib/compress/zstd_double_fast.c
@@ -392,7 +392,7 @@ size_t ZSTD_compressBlock_doubleFast_dictMatchState_generic(
         hashLong[h2] = hashSmall[h] = curr;   /* update hash tables */
 
         /* check repcode */
-        if (((U32)((prefixLowestIndex-1) - repIndex) >= 3 /* intentional underflow */)
+        if ((ZSTD_index_overlap_check(prefixLowestIndex, repIndex))
             && (MEM_read32(repMatch) == MEM_read32(ip+1)) ) {
             const BYTE* repMatchEnd = repIndex < prefixLowestIndex ? dictEnd : iend;
             mLength = ZSTD_count_2segments(ip+1+4, repMatch+4, iend, repMatchEnd, prefixLowest) + 4;
@@ -513,7 +513,7 @@ _match_stored:
                 const BYTE* repMatch2 = repIndex2 < prefixLowestIndex ?
                         dictBase + repIndex2 - dictIndexDelta :
                         base + repIndex2;
-                if ( ((U32)((prefixLowestIndex-1) - (U32)repIndex2) >= 3 /* intentional overflow */)
+                if ( (ZSTD_index_overlap_check(prefixLowestIndex, repIndex2))
                    && (MEM_read32(repMatch2) == MEM_read32(ip)) ) {
                     const BYTE* const repEnd2 = repIndex2 < prefixLowestIndex ? dictEnd : iend;
                     size_t const repLength2 = ZSTD_count_2segments(ip+4, repMatch2+4, iend, repEnd2, prefixLowest) + 4;
@@ -651,7 +651,7 @@ size_t ZSTD_compressBlock_doubleFast_extDict_generic(
         size_t mLength;
         hashSmall[hSmall] = hashLong[hLong] = curr;   /* update hash table */
 
-        if ((((U32)((prefixStartIndex-1) - repIndex) >= 3) /* intentional underflow : ensure repIndex doesn't overlap dict + prefix */
+        if (((ZSTD_index_overlap_check(prefixStartIndex, repIndex)) 
             & (offset_1 <= curr+1 - dictStartIndex)) /* note: we are searching at curr+1 */
           && (MEM_read32(repMatch) == MEM_read32(ip+1)) ) {
             const BYTE* repMatchEnd = repIndex < prefixStartIndex ? dictEnd : iend;
@@ -719,7 +719,7 @@ size_t ZSTD_compressBlock_doubleFast_extDict_generic(
                 U32 const current2 = (U32)(ip-base);
                 U32 const repIndex2 = current2 - offset_2;
                 const BYTE* repMatch2 = repIndex2 < prefixStartIndex ? dictBase + repIndex2 : base + repIndex2;
-                if ( (((U32)((prefixStartIndex-1) - repIndex2) >= 3)   /* intentional overflow : ensure repIndex2 doesn't overlap dict + prefix */
+                if ( ((ZSTD_index_overlap_check(prefixStartIndex, repIndex2))
                     & (offset_2 <= current2 - dictStartIndex))
                   && (MEM_read32(repMatch2) == MEM_read32(ip)) ) {
                     const BYTE* const repEnd2 = repIndex2 < prefixStartIndex ? dictEnd : iend;

diff --git a/lib/compress/zstd_fast.c b/lib/compress/zstd_fast.c
index 6c4554cfca71fc5b9a5cbfbf0449bf32e4504184..c6baa49d4dd0a576c943be0463b6a7a2c2aff1ea 100644 (file)
--- a/lib/compress/zstd_fast.c
+++ b/lib/compress/zstd_fast.c
@@ -546,8 +546,7 @@ size_t ZSTD_compressBlock_fast_dictMatchState_generic(
             size_t const dictHashAndTag1 = ZSTD_hashPtr(ip1, dictHBits, mls);
             hashTable[hash0] = curr;   /* update hash table */
 
-            if (((U32) ((prefixStartIndex - 1) - repIndex) >=
-                 3) /* intentional underflow : ensure repIndex isn't overlapping dict + prefix */
+            if ((ZSTD_index_overlap_check(prefixStartIndex, repIndex)) 
                 && (MEM_read32(repMatch) == MEM_read32(ip0 + 1))) {
                 const BYTE* const repMatchEnd = repIndex < prefixStartIndex ? dictEnd : iend;
                 mLength = ZSTD_count_2segments(ip0 + 1 + 4, repMatch + 4, iend, repMatchEnd, prefixStart) + 4;
@@ -631,7 +630,7 @@ size_t ZSTD_compressBlock_fast_dictMatchState_generic(
                 const BYTE* repMatch2 = repIndex2 < prefixStartIndex ?
                         dictBase - dictIndexDelta + repIndex2 :
                         base + repIndex2;
-                if ( ((U32)((prefixStartIndex-1) - (U32)repIndex2) >= 3 /* intentional overflow */)
+                if ( (ZSTD_index_overlap_check(prefixStartIndex, repIndex2))
                    && (MEM_read32(repMatch2) == MEM_read32(ip0))) {
                     const BYTE* const repEnd2 = repIndex2 < prefixStartIndex ? dictEnd : iend;
                     size_t const repLength2 = ZSTD_count_2segments(ip0+4, repMatch2+4, iend, repEnd2, prefixStart) + 4;
@@ -925,7 +924,7 @@ _match: /* Requires: ip0, match0, offcode, matchEnd */
         while (ip0 <= ilimit) {
             U32 const repIndex2 = (U32)(ip0-base) - offset_2;
             const BYTE* const repMatch2 = repIndex2 < prefixStartIndex ? dictBase + repIndex2 : base + repIndex2;
-            if ( (((U32)((prefixStartIndex-1) - repIndex2) >= 3) & (offset_2 > 0))  /* intentional underflow */
+            if ( ((ZSTD_index_overlap_check(prefixStartIndex, repIndex2)) & (offset_2 > 0))
                  && (MEM_read32(repMatch2) == MEM_read32(ip0)) ) {
                 const BYTE* const repEnd2 = repIndex2 < prefixStartIndex ? dictEnd : iend;
                 size_t const repLength2 = ZSTD_count_2segments(ip0+4, repMatch2+4, iend, repEnd2, prefixStart) + 4;

diff --git a/lib/compress/zstd_lazy.c b/lib/compress/zstd_lazy.c
index 67dd55fdb8060394698e2576e90154c328364e2a..9efaf4b25d0b315577842344bcf21ea9177bce2b 100644 (file)
--- a/lib/compress/zstd_lazy.c
+++ b/lib/compress/zstd_lazy.c
@@ -1590,7 +1590,7 @@ size_t ZSTD_compressBlock_lazy_generic(
                                 && repIndex < prefixLowestIndex) ?
                                    dictBase + (repIndex - dictIndexDelta) :
                                    base + repIndex;
-            if (((U32)((prefixLowestIndex-1) - repIndex) >= 3 /* intentional underflow */)
+            if ((ZSTD_index_overlap_check(prefixLowestIndex, repIndex))
                 && (MEM_read32(repMatch) == MEM_read32(ip+1)) ) {
                 const BYTE* repMatchEnd = repIndex < prefixLowestIndex ? dictEnd : iend;
                 matchLength = ZSTD_count_2segments(ip+1+4, repMatch+4, iend, repMatchEnd, prefixLowest) + 4;
@@ -1642,7 +1642,7 @@ size_t ZSTD_compressBlock_lazy_generic(
                 const BYTE* repMatch = repIndex < prefixLowestIndex ?
                                dictBase + (repIndex - dictIndexDelta) :
                                base + repIndex;
-                if (((U32)((prefixLowestIndex-1) - repIndex) >= 3 /* intentional underflow */)
+                if ((ZSTD_index_overlap_check(prefixLowestIndex, repIndex))
                     && (MEM_read32(repMatch) == MEM_read32(ip)) ) {
                     const BYTE* repMatchEnd = repIndex < prefixLowestIndex ? dictEnd : iend;
                     size_t const mlRep = ZSTD_count_2segments(ip+4, repMatch+4, iend, repMatchEnd, prefixLowest) + 4;
@@ -1678,7 +1678,7 @@ size_t ZSTD_compressBlock_lazy_generic(
                     const BYTE* repMatch = repIndex < prefixLowestIndex ?
                                    dictBase + (repIndex - dictIndexDelta) :
                                    base + repIndex;
-                    if (((U32)((prefixLowestIndex-1) - repIndex) >= 3 /* intentional underflow */)
+                    if ((ZSTD_index_overlap_check(prefixLowestIndex, repIndex))
                         && (MEM_read32(repMatch) == MEM_read32(ip)) ) {
                         const BYTE* repMatchEnd = repIndex < prefixLowestIndex ? dictEnd : iend;
                         size_t const mlRep = ZSTD_count_2segments(ip+4, repMatch+4, iend, repMatchEnd, prefixLowest) + 4;
@@ -1740,7 +1740,7 @@ _storeSequence:
                 const BYTE* repMatch = repIndex < prefixLowestIndex ?
                         dictBase - dictIndexDelta + repIndex :
                         base + repIndex;
-                if ( ((U32)((prefixLowestIndex-1) - (U32)repIndex) >= 3 /* intentional overflow */)
+                if ( (ZSTD_index_overlap_check(prefixLowestIndex, repIndex))
                    && (MEM_read32(repMatch) == MEM_read32(ip)) ) {
                     const BYTE* const repEnd2 = repIndex < prefixLowestIndex ? dictEnd : iend;
                     matchLength = ZSTD_count_2segments(ip+4, repMatch+4, iend, repEnd2, prefixLowest) + 4;
@@ -1986,7 +1986,7 @@ size_t ZSTD_compressBlock_lazy_extDict_generic(
             const U32 repIndex = (U32)(curr+1 - offset_1);
             const BYTE* const repBase = repIndex < dictLimit ? dictBase : base;
             const BYTE* const repMatch = repBase + repIndex;
-            if ( ((U32)((dictLimit-1) - repIndex) >= 3) /* intentional overflow */
+            if ( (ZSTD_index_overlap_check(dictLimit, repIndex))
                & (offset_1 <= curr+1 - windowLow) ) /* note: we are searching at curr+1 */
             if (MEM_read32(ip+1) == MEM_read32(repMatch)) {
                 /* repcode detected we should take it */
@@ -2027,7 +2027,7 @@ size_t ZSTD_compressBlock_lazy_extDict_generic(
                 const U32 repIndex = (U32)(curr - offset_1);
                 const BYTE* const repBase = repIndex < dictLimit ? dictBase : base;
                 const BYTE* const repMatch = repBase + repIndex;
-                if ( ((U32)((dictLimit-1) - repIndex) >= 3) /* intentional overflow : do not test positions overlapping 2 memory segments  */
+                if ( (ZSTD_index_overlap_check(dictLimit, repIndex))
                    & (offset_1 <= curr - windowLow) ) /* equivalent to `curr > repIndex >= windowLow` */
                 if (MEM_read32(ip) == MEM_read32(repMatch)) {
                     /* repcode detected */
@@ -2059,7 +2059,7 @@ size_t ZSTD_compressBlock_lazy_extDict_generic(
                     const U32 repIndex = (U32)(curr - offset_1);
                     const BYTE* const repBase = repIndex < dictLimit ? dictBase : base;
                     const BYTE* const repMatch = repBase + repIndex;
-                    if ( ((U32)((dictLimit-1) - repIndex) >= 3) /* intentional overflow : do not test positions overlapping 2 memory segments  */
+                    if ( (ZSTD_index_overlap_check(dictLimit, repIndex))
                        & (offset_1 <= curr - windowLow) ) /* equivalent to `curr > repIndex >= windowLow` */
                     if (MEM_read32(ip) == MEM_read32(repMatch)) {
                         /* repcode detected */
@@ -2113,7 +2113,7 @@ _storeSequence:
             const U32 repIndex = repCurrent - offset_2;
             const BYTE* const repBase = repIndex < dictLimit ? dictBase : base;
             const BYTE* const repMatch = repBase + repIndex;
-            if ( ((U32)((dictLimit-1) - repIndex) >= 3) /* intentional overflow : do not test positions overlapping 2 memory segments  */
+            if ( (ZSTD_index_overlap_check(dictLimit, repIndex))
                & (offset_2 <= repCurrent - windowLow) ) /* equivalent to `curr > repIndex >= windowLow` */
             if (MEM_read32(ip) == MEM_read32(repMatch)) {
                 /* repcode detected we should take it */

diff --git a/lib/compress/zstd_opt.c b/lib/compress/zstd_opt.c
index e63073e5a4f3e4a3a8c7a85b84a1b809e0ebd335..8a4345b317c82912e24cbfd746eba5d050b62138 100644 (file)
--- a/lib/compress/zstd_opt.c
+++ b/lib/compress/zstd_opt.c
@@ -664,13 +664,13 @@ ZSTD_insertBtAndGetAllMatches (
                 assert(curr >= windowLow);
                 if ( dictMode == ZSTD_extDict
                   && ( ((repOffset-1) /*intentional overflow*/ < curr - windowLow)  /* equivalent to `curr > repIndex >= windowLow` */
-                     & (((U32)((dictLimit-1) - repIndex) >= 3) ) /* intentional overflow : do not test positions overlapping 2 memory segments */)
+                     & (ZSTD_index_overlap_check(dictLimit, repIndex)) )
                   && (ZSTD_readMINMATCH(ip, minMatch) == ZSTD_readMINMATCH(repMatch, minMatch)) ) {
                     repLen = (U32)ZSTD_count_2segments(ip+minMatch, repMatch+minMatch, iLimit, dictEnd, prefixStart) + minMatch;
                 }
                 if (dictMode == ZSTD_dictMatchState
                   && ( ((repOffset-1) /*intentional overflow*/ < curr - (dmsLowLimit + dmsIndexDelta))  /* equivalent to `curr > repIndex >= dmsLowLimit` */
-                     & ((U32)((dictLimit-1) - repIndex) >= 3) ) /* intentional overflow : do not test positions overlapping 2 memory segments */
+                     & (ZSTD_index_overlap_check(dictLimit, repIndex)) )
                   && (ZSTD_readMINMATCH(ip, minMatch) == ZSTD_readMINMATCH(repMatch, minMatch)) ) {
                     repLen = (U32)ZSTD_count_2segments(ip+minMatch, repMatch+minMatch, iLimit, dmsEnd, prefixStart) + minMatch;
             }   }