From: Yann Collet <cyan@fb.com>
Date: Wed, 24 May 2017 20:15:19 +0000 (-0700)
Subject: fixed performance regression with ZSTD_decompress() on small files
X-Git-Tag: v1.3.0~1^2~17^2~84
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2e4db3e531e224118a316d50174300116a2f99ca;p=thirdparty%2Fzstd.git

fixed performance regression with ZSTD_decompress() on small files

memset() was a quick fix to initialization problems,
but initialize too much space (tables, buffers)
which show up in decompression speed of ZSTD_decompress()
since it needs to recreate DCtx at each invocation.

Fixed by only initialization relevant pointers and size fields.
---

diff --git a/lib/decompress/zstd_decompress.c b/lib/decompress/zstd_decompress.c
index aabfa6d94..8cf500445 100644
--- a/lib/decompress/zstd_decompress.c
+++ b/lib/decompress/zstd_decompress.c
@@ -195,11 +195,16 @@ ZSTD_DCtx* ZSTD_createDCtx_advanced(ZSTD_customMem customMem)
 
     dctx = (ZSTD_DCtx*)ZSTD_malloc(sizeof(ZSTD_DCtx), customMem);
     if (!dctx) return NULL;
-    memset(dctx, 0, sizeof(*dctx));
     memcpy(&dctx->customMem, &customMem, sizeof(customMem));
     ZSTD_decompressBegin(dctx);   /* cannot fail */
     dctx->streamStage = zdss_init;
     dctx->maxWindowSize = ZSTD_MAXWINDOWSIZE_DEFAULT;
+    dctx->ddict   = NULL;
+    dctx->ddictLocal = NULL;
+    dctx->inBuff  = NULL;
+    dctx->outBuff = NULL;
+    dctx->inBuffSize = 0;
+    dctx->outBuffSize= 0;
     return dctx;
 }