From: Yann Collet <cyan@fb.com>
Date: Sun, 1 Oct 2017 18:32:38 +0000 (-0700)
Subject: added comment on ZSTD_COMPRESSBOUND()
X-Git-Tag: v1.3.2~3^2~13^2^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5db19b8685e4287de4a3231f31c4bf0e649783db;p=thirdparty%2Fzstd.git

added comment on ZSTD_COMPRESSBOUND()

as requested by @terrelln
---

diff --git a/lib/zstd.h b/lib/zstd.h
index 02491ed40..4e225bb5e 100644
--- a/lib/zstd.h
+++ b/lib/zstd.h
@@ -131,7 +131,7 @@ ZSTDLIB_API unsigned long long ZSTD_getDecompressedSize(const void* src, size_t
 
 
 /*======  Helper functions  ======*/
-#define ZSTD_COMPRESSBOUND(srcSize)   ((srcSize) + ((srcSize)>>8) + (((srcSize) < 128 KB) ? ((128 KB - (srcSize)) >> 11) /* margin, from 64 to 0 */ : 0))
+#define ZSTD_COMPRESSBOUND(srcSize)   ((srcSize) + ((srcSize)>>8) + (((srcSize) < 128 KB) ? ((128 KB - (srcSize)) >> 11) /* margin, from 64 to 0 */ : 0))  /* this formula ensures that bound(A) + bound(B) <= bound(A+B) as long as A and B >= 128 KB */
 ZSTDLIB_API size_t      ZSTD_compressBound(size_t srcSize); /*!< maximum compressed size in worst case scenario */
 ZSTDLIB_API unsigned    ZSTD_isError(size_t code);          /*!< tells if a `size_t` function result is an error code */
 ZSTDLIB_API const char* ZSTD_getErrorName(size_t code);     /*!< provides readable string from an error code */