From ac45e078a5bc22e06d1be1375c25795b7ef3c1ff Mon Sep 17 00:00:00 2001 From: Yann Collet Date: Thu, 12 Jan 2023 15:49:01 -0800 Subject: [PATCH] add explanation about new test as requested by @terrelln --- lib/compress/zstd_compress_literals.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/lib/compress/zstd_compress_literals.c b/lib/compress/zstd_compress_literals.c index e84781873..0dbc2c4d4 100644 --- a/lib/compress/zstd_compress_literals.c +++ b/lib/compress/zstd_compress_literals.c @@ -187,6 +187,11 @@ size_t ZSTD_compressLiterals ( return ZSTD_noCompressLiterals(dst, dstCapacity, src, srcSize); } } if (cLitSize==1) { + /* A return value of 1 signals that the alphabet consists of a single symbol. + * However, in some rare circumstances, it could be the compressed size (a single byte). + * For that outcome to have a chance to happen, it's necessary that `srcSize < 8`. + * (it's also necessary to not generate statistics). + * Therefore, in such a case, actively check that all bytes are identical. */ if ((srcSize >= 8) || allBytesIdentical(src, srcSize)) { ZSTD_memcpy(nextHuf, prevHuf, sizeof(*prevHuf)); return ZSTD_compressRleLiteralsBlock(dst, dstCapacity, src, srcSize); -- 2.47.2