From: senhuang42 <senhuang96@fb.com>
Date: Sat, 26 Sep 2020 16:09:19 +0000 (-0400)
Subject: Implement basic splitSequence and skipSequence functions
X-Git-Tag: v1.4.7~57^2~45
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=28c74bf591bf18800d292353b4e1cb0c4b378129;p=thirdparty%2Fzstd.git

Implement basic splitSequence and skipSequence functions
---

diff --git a/lib/compress/zstd_opt.c b/lib/compress/zstd_opt.c
index 0680e831b..6c8e8cc1d 100644
--- a/lib/compress/zstd_opt.c
+++ b/lib/compress/zstd_opt.c
@@ -768,15 +768,61 @@ FORCE_INLINE_TEMPLATE U32 ZSTD_BtGetAllMatches (
 *  LDM util functions
 *********************************/
 
+
+static void ldm_skipSequences(rawSeqStore_t* rawSeqStore, size_t srcSize, U32 const minMatch) {
+    while (srcSize > 0 && rawSeqStore->pos < rawSeqStore->size) {
+        rawSeq* seq = rawSeqStore->seq + rawSeqStore->pos;
+        if (srcSize <= seq->litLength) {
+            /* Skip past srcSize literals */
+            seq->litLength -= (U32)srcSize;
+            return;
+        }
+        srcSize -= seq->litLength;
+        seq->litLength = 0;
+        if (srcSize < seq->matchLength) {
+            /* Skip past the first srcSize of the match */
+            seq->matchLength -= (U32)srcSize;
+            if (seq->matchLength < minMatch) {
+                /* The match is too short, omit it */
+                if (rawSeqStore->pos + 1 < rawSeqStore->size) {
+                    seq[1].litLength += seq[0].matchLength;
+                }
+                rawSeqStore->pos++;
+            }
+            return;
+        }
+        srcSize -= seq->matchLength;
+        seq->matchLength = 0;
+        rawSeqStore->pos++;
+    }
+}
+
 // The only function that can update pos (i think, for now)
-static int ldm_splitSequence(rawSeqStore_t* ldmSeqStore, U32 remainingBytes) {
+static rawSeq ldm_splitSequence(rawSeqStore_t* ldmSeqStore, U32 remainingBytes) {
     rawSeq currSeq = ldmSeqStore->seq[ldmSeqStore->pos];
+    /* No split */
+    if (remainingBytes >= currSeq.litLength + currSeq.matchLength) {
+        ldmSeqStore->pos++;
+        return currSeq;
+    }
+    /* Need a split */
+    if (remainingBytes <= currSeq.litLength) {
+        currSeq.offset = 0;
+    } else if (remainingBytes < currSeq.litLength + currSeq.matchLength) {
+        if (currSeq.matchLength < MINMATCH) {
+            currSeq.offset = 0;
+        }
+    }
 
+    ldm_skipSequences(ldmSeqStore, remainingBytes, MINMATCH);
+    return currSeq;
 }
 
 /* Returns 1 if the rest of the block is just LDM literals */
-static int ldm_getNextMatch(U32* matchStartPosInBlock, U32* matchEndPosInBlock, U32 remainingBytes) {
-    int ret = ldm_splitSequence();
+static int ldm_getNextMatch(rawSeqStore_t* ldmSeqStore,
+                            U32* matchStartPosInBlock, U32* matchEndPosInBlock,
+                            U32 remainingBytes) {
+    int ret = ldm_splitSequence(ldmSeqStore, remainingBytes);
 }
 
 /* Adds an LDM if it's long enough */