From: Sen Huang <senhuang96@fb.com>
Date: Mon, 22 Mar 2021 21:38:21 +0000 (-0700)
Subject: Add a fallback in case the total blocksize of split blocks exceeds raw block size
X-Git-Tag: v1.5.0^2~75^2~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0ef1f935b787aec0f6eab95c93538ef24e87e15a;p=thirdparty%2Fzstd.git

Add a fallback in case the total blocksize of split blocks exceeds raw block size
---

diff --git a/lib/compress/zstd_compress.c b/lib/compress/zstd_compress.c
index d29825c46..fe1516b79 100644
--- a/lib/compress/zstd_compress.c
+++ b/lib/compress/zstd_compress.c
@@ -3327,6 +3327,7 @@ static size_t ZSTD_compressBlock_splitBlock_internal(ZSTD_CCtx* zc, void* dst, s
     seqStore_t nextSeqStore;
     seqStore_t currSeqStore;
     U32 canEmitRLEorNoCompress = 1;
+    const size_t dstCapacityInitial = dstCapacity;
 
     DEBUGLOG(5, "ZSTD_compressBlock_splitBlock_internal (dstCapacity=%u, dictLimit=%u, nextToUpdate=%u)",
                 (unsigned)dstCapacity, (unsigned)zc->blockState.matchState.window.dictLimit,
@@ -3370,6 +3371,14 @@ static size_t ZSTD_compressBlock_splitBlock_internal(ZSTD_CCtx* zc, void* dst, s
         cSize += cSizeChunk;
         currSeqStore = nextSeqStore;
     }
+
+    if (cSize > ZSTD_BLOCKSIZE_MAX + ZSTD_blockHeaderSize) {
+        /* If too large, recompress the original block to avoid any chance of a single block exceeding ZSTD_BLOCKSIZE_MAX */
+        cSize = ZSTD_compressSequences_singleBlock(zc, &zc->seqStore, (BYTE*)dst, dstCapacityInitial, (const BYTE*)src, blockSize, lastBlock, 1);
+        FORWARD_IF_ERROR(cSize, "Compressing single block from splitBlock_internal() fallback failed!");
+        DEBUGLOG(5, "ZSTD_compressBlock_splitBlock_internal: Compressed split block too large, recompressed");
+    }
+    assert(cSize <= ZSTD_BLOCKSIZE_MAX + ZSTD_blockHeaderSize);
     return cSize;
 }