From: Nick Terrell <terrelln@fb.com>
Date: Thu, 5 Mar 2020 00:29:19 +0000 (-0800)
Subject: [opt] Explain why we don't include literals price
X-Git-Tag: v1.4.5^2~81^2~1
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=610171ed86b947431796ec58854a673c674f6602;p=thirdparty%2Fzstd.git

[opt] Explain why we don't include literals price
---

diff --git a/lib/compress/zstd_opt.c b/lib/compress/zstd_opt.c
index 44a13ddb7..896365fc8 100644
--- a/lib/compress/zstd_opt.c
+++ b/lib/compress/zstd_opt.c
@@ -881,6 +881,11 @@ ZSTD_compressBlock_opt_generic(ZSTD_matchState_t* ms,
             { U32 i ; for (i=0; i<ZSTD_REP_NUM; i++) opt[0].rep[i] = rep[i]; }
             opt[0].mlen = 0;  /* means is_a_literal */
             opt[0].litlen = litlen;
+            /* We don't need to include the actual price of the literals because
+             * it is static for the duration of the forward pass, and is included
+             * in every price. We include the literal length to avoid negative
+             * prices when we subtract the previous literal length.
+             */
             opt[0].price = ZSTD_litLengthPrice(litlen, optStatePtr, optLevel);
 
             /* large match -> immediate encoding */