From: Yann Collet <cyan@fb.com>
Date: Sat, 1 Apr 2017 00:11:38 +0000 (-0700)
Subject: Changed ZSTD_compressBound()
X-Git-Tag: v1.2.0^2~67^2~3
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3f75d5252766bf0e638cf3fb7f5d63da50baaefe;p=thirdparty%2Fzstd.git

Changed ZSTD_compressBound()

required so that if Total = A+B
compressBound(Total) <= compressBound(A) + compressBound(B)
under condition of a minimum size for A and B

Will help for ZSTDMT_compress() memory allocation
---

diff --git a/lib/compress/zstd_compress.c b/lib/compress/zstd_compress.c
index c31f8db91..cc69f1184 100644
--- a/lib/compress/zstd_compress.c
+++ b/lib/compress/zstd_compress.c
@@ -32,7 +32,10 @@ typedef enum { ZSTDcs_created=0, ZSTDcs_init, ZSTDcs_ongoing, ZSTDcs_ending } ZS
 *  Helper functions
 ***************************************/
 #define ZSTD_STATIC_ASSERT(c) { enum { ZSTD_static_assert = 1/(int)(!!(c)) }; }
-size_t ZSTD_compressBound(size_t srcSize) { return FSE_compressBound(srcSize) + 12; }
+size_t ZSTD_compressBound(size_t srcSize) {
+    size_t const margin = (srcSize < 512 KB) ? 16 : 0;
+    return srcSize + (srcSize >> 8) + margin;
+}
 
 
 /*-*************************************