Fix null pointer addition

lib/compress/zstd_compress.c

@@ -1336,10 +1336,7 @@ ZSTD_reset_matchState(ZSTD_matchState_t* ms,
 
     DEBUGLOG(4, "reset indices : %u", forceResetIndex == ZSTDirp_reset);
     if (forceResetIndex == ZSTDirp_reset) {
-        memset(&ms->window, 0, sizeof(ms->window));
-        ms->window.dictLimit = 1;    /* start from 1, so that 1st position is valid */
-        ms->window.lowLimit = 1;     /* it ensures first and later CCtx usages compress the same */
-        ms->window.nextSrc = ms->window.base + 1;   /* see issue #1241 */
+        ZSTD_window_init(&ms->window);
         ZSTD_cwksp_mark_tables_dirty(ws);
     }
 
@@ -1432,7 +1429,7 @@ static size_t ZSTD_resetCCtx_internal(ZSTD_CCtx* zc,
         size_t const matchStateSize = ZSTD_sizeof_matchState(&params.cParams, /* forCCtx */ 1);
         size_t const maxNbLdmSeq = ZSTD_ldm_getMaxNbSeq(params.ldmParams, blockSize);
 
-        ZSTD_indexResetPolicy_e needsIndexReset = ZSTDirp_continue;
+        ZSTD_indexResetPolicy_e needsIndexReset = zc->initialized ? ZSTDirp_continue : ZSTDirp_reset;
 
         if (ZSTD_indexTooCloseToMax(zc->blockState.matchState.window)) {
             needsIndexReset = ZSTDirp_reset;
@@ -1557,11 +1554,12 @@ static size_t ZSTD_resetCCtx_internal(ZSTD_CCtx* zc,
             zc->ldmSequences = (rawSeq*)ZSTD_cwksp_reserve_aligned(ws, maxNbLdmSeq * sizeof(rawSeq));
             zc->maxNbLdmSequences = maxNbLdmSeq;
 
-            memset(&zc->ldmState.window, 0, sizeof(zc->ldmState.window));
+            ZSTD_window_init(&zc->ldmState.window);
             ZSTD_window_clear(&zc->ldmState.window);
         }
 
         DEBUGLOG(3, "wksp: finished allocating, %zd bytes remain available", ZSTD_cwksp_available_space(ws));
+        zc->initialized = 1;
 
         return 0;
     }
@@ -3757,11 +3755,11 @@ static size_t ZSTD_compressStream_generic(ZSTD_CStream* zcs,
                                           ZSTD_EndDirective const flushMode)
 {
     const char* const istart = (const char*)input->src;
-    const char* const iend = istart + input->size;
-    const char* ip = istart + input->pos;
+    const char* const iend = input->size != 0 ? istart + input->size : istart;
+    const char* ip = input->pos != 0 ? istart + input->pos : istart;
     char* const ostart = (char*)output->dst;
-    char* const oend = ostart + output->size;
-    char* op = ostart + output->pos;
+    char* const oend = output->size != 0 ? ostart + output->size : ostart;
+    char* op = output->pos != 0 ? ostart + output->pos : ostart;
     U32 someMoreWork = 1;
 
     /* check expectations */
@@ -3800,7 +3798,8 @@ static size_t ZSTD_compressStream_generic(ZSTD_CStream* zcs,
                                         zcs->inBuff + zcs->inBuffPos, toLoad,
                                         ip, iend-ip);
                 zcs->inBuffPos += loaded;
-                ip += loaded;
+                if (loaded != 0)
+                    ip += loaded;
                 if ( (flushMode == ZSTD_e_continue)
                   && (zcs->inBuffPos < zcs->inBuffTarget) ) {
                     /* not enough input to fill full block : stop here */
@@ -3860,7 +3859,8 @@ static size_t ZSTD_compressStream_generic(ZSTD_CStream* zcs,
                             zcs->outBuff + zcs->outBuffFlushedSize, toFlush);
                 DEBUGLOG(5, "toFlush: %u into %u ==> flushed: %u",
                             (unsigned)toFlush, (unsigned)(oend-op), (unsigned)flushed);
-                op += flushed;
+                if (flushed)
+                    op += flushed;
                 zcs->outBuffFlushedSize += flushed;
                 if (toFlush!=flushed) {
                     /* flush not fully completed, presumably because dst is too small */

lib/compress/zstd_compress_internal.h

@@ -249,6 +249,7 @@ struct ZSTD_CCtx_s {
     size_t staticSize;
     SeqCollector seqCollector;
     int isFirstBlock;
+    int initialized;
 
     seqStore_t seqStore;      /* sequences storage ptrs */
     ldmState_t ldmState;      /* long distance matching state */
@@ -858,6 +859,15 @@ ZSTD_checkDictValidity(const ZSTD_window_t* window,
     }   }   }
 }
 
+MEM_STATIC void ZSTD_window_init(ZSTD_window_t* window) {
+    memset(window, 0, sizeof(*window));
+    window->base = (BYTE const*)"";
+    window->dictBase = (BYTE const*)"";
+    window->dictLimit = 1;    /* start from 1, so that 1st position is valid */
+    window->lowLimit = 1;     /* it ensures first and later CCtx usages compress the same */
+    window->nextSrc = window->base + 1;   /* see issue #1241 */
+}
+
 /**
  * ZSTD_window_update():
  * Updates the window by appending [src, src + srcSize) to the window.
@@ -871,6 +881,10 @@ MEM_STATIC U32 ZSTD_window_update(ZSTD_window_t* window,
     BYTE const* const ip = (BYTE const*)src;
     U32 contiguous = 1;
     DEBUGLOG(5, "ZSTD_window_update");
+    if (srcSize == 0)
+        return contiguous;
+    assert(window->base != NULL);
+    assert(window->dictBase != NULL);
     /* Check if blocks follow each other */
     if (src != window->nextSrc) {
         /* not contiguous */

lib/compress/zstd_double_fast.c

@@ -96,7 +96,7 @@ size_t ZSTD_compressBlock_doubleFast_generic(
                                      dictCParams->hashLog : hBitsL;
     const U32 dictHBitsS           = dictMode == ZSTD_dictMatchState ?
                                      dictCParams->chainLog : hBitsS;
-    const U32 dictAndPrefixLength  = (U32)(ip - prefixLowest + dictEnd - dictStart);
+    const U32 dictAndPrefixLength  = (U32)((ip - prefixLowest) + (dictEnd - dictStart));
 
     DEBUGLOG(5, "ZSTD_compressBlock_doubleFast_generic");
 
@@ -271,7 +271,7 @@ _match_stored:
                     U32 const repIndex2 = current2 - offset_2;
                     const BYTE* repMatch2 = dictMode == ZSTD_dictMatchState
                         && repIndex2 < prefixLowestIndex ?
-                            dictBase - dictIndexDelta + repIndex2 :
+                            dictBase + repIndex2 - dictIndexDelta :
                             base + repIndex2;
                     if ( ((U32)((prefixLowestIndex-1) - (U32)repIndex2) >= 3 /* intentional overflow */)
                        && (MEM_read32(repMatch2) == MEM_read32(ip)) ) {

lib/compress/zstd_lazy.c

@@ -660,7 +660,7 @@ ZSTD_compressBlock_lazy_generic(
     const U32 dictIndexDelta       = dictMode == ZSTD_dictMatchState ?
                                      prefixLowestIndex - (U32)(dictEnd - dictBase) :
                                      0;
-    const U32 dictAndPrefixLength = (U32)(ip - prefixLowest + dictEnd - dictLowest);
+    const U32 dictAndPrefixLength = (U32)((ip - prefixLowest) + (dictEnd - dictLowest));
 
     /* init */
     ip += (dictAndPrefixLength == 0);

lib/compress/zstdmt_compress.c

@@ -490,7 +490,7 @@ static int ZSTDMT_serialState_reset(serialState_t* serialState, ZSTDMT_seqPool*
         /* Size the seq pool tables */
         ZSTDMT_setNbSeq(seqPool, ZSTD_ldm_getMaxNbSeq(params.ldmParams, jobSize));
         /* Reset the window */
-        ZSTD_window_clear(&serialState->ldmState.window);
+        ZSTD_window_init(&serialState->ldmState.window);
         serialState->ldmWindow = serialState->ldmState.window;
         /* Resize tables and output space if necessary. */
         if (serialState->ldmState.hashTable == NULL || serialState->params.ldmParams.hashLog < hashLog) {
@@ -1786,7 +1786,7 @@ static int ZSTDMT_isOverlapped(buffer_t buffer, range_t range)
     BYTE const* const bufferStart = (BYTE const*)buffer.start;
     BYTE const* const bufferEnd = bufferStart + buffer.capacity;
     BYTE const* const rangeStart = (BYTE const*)range.start;
-    BYTE const* const rangeEnd = rangeStart + range.size;
+    BYTE const* const rangeEnd = range.size != 0 ? rangeStart + range.size : rangeStart;
 
     if (rangeStart == NULL || bufferStart == NULL)
         return 0;