From: senhuang42 <senhuang96@fb.com>
Date: Mon, 2 Nov 2020 21:59:16 +0000 (-0500)
Subject: Change block delimiter removing to linear time approach
X-Git-Tag: v1.4.7~34^2~4
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f782cac3d4b93739b918bc20c3d458febbe81a58;p=thirdparty%2Fzstd.git

Change block delimiter removing to linear time approach
---

diff --git a/lib/compress/zstd_compress.c b/lib/compress/zstd_compress.c
index 7571261a4..928f8fef0 100644
--- a/lib/compress/zstd_compress.c
+++ b/lib/compress/zstd_compress.c
@@ -2569,22 +2569,22 @@ size_t ZSTD_getSequences(ZSTD_CCtx* zc, ZSTD_Sequence* outSeqs,
     ZSTD_customFree(dst, ZSTD_defaultCMem);
 
     if (format == ZSTD_sf_noBlockDelimiters) {
-        size_t i = 0;
-        size_t totalSeqs = zc->seqCollector.seqIndex;
-        while(i < totalSeqs) {
-            if (seqCollector.seqStart[i].offset == 0 && seqCollector.seqStart[i].matchLength == 0) {
-                /* Merge the block boundary or last literals */
-                if (i != totalSeqs-1) {
-                    /* Add last literals to next sequence, then "delete" this sequence */
-                    seqCollector.seqStart[i+1].litLength += seqCollector.seqStart[i].litLength;
-                    ZSTD_memmove(seqCollector.seqStart+i, seqCollector.seqStart+i+1, (totalSeqs-i-1)*sizeof(ZSTD_Sequence));
+        /* Remove all block delimiters and append them to the next sequence's literals
+         * and do not emit last literals at all
+         */
+        size_t in = 0;
+        size_t out = 0;
+        for (; in < zc->seqCollector.seqIndex; ++in) {
+            if (seqCollector.seqStart[in].offset == 0 && seqCollector.seqStart[in].matchLength == 0) {
+                if (in != zc->seqCollector.seqIndex - 1) {
+                    seqCollector.seqStart[in+1].litLength += seqCollector.seqStart[in].litLength;
                 }
-                totalSeqs--;
             } else {
-                ++i;
+                seqCollector.seqStart[out] = seqCollector.seqStart[in];
+                ++out;
             }
         }
-        zc->seqCollector.seqIndex = totalSeqs;
+        zc->seqCollector.seqIndex = out;
     }
 
     return zc->seqCollector.seqIndex;