From: Sean Purcell <me@seanp.xyz>
Date: Wed, 22 Feb 2017 21:29:01 +0000 (-0800)
Subject: Describe ambiguity around skippable frames
X-Git-Tag: v1.1.4~1^2~48^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F560%2Fhead;p=thirdparty%2Fzstd.git

Describe ambiguity around skippable frames
---

diff --git a/lib/zstd.h b/lib/zstd.h
index 49050607e..e597c5db5 100644
--- a/lib/zstd.h
+++ b/lib/zstd.h
@@ -700,6 +700,9 @@ ZSTDLIB_API size_t ZSTD_compressEnd(ZSTD_CCtx* cctx, void* dst, size_t dstCapaci
   c) Frame Content - any content (User Data) of length equal to Frame Size
   For skippable frames ZSTD_decompressContinue() always returns 0.
   For skippable frames ZSTD_getFrameParams() returns fparamsPtr->windowLog==0 what means that a frame is skippable.
+    Note : If fparamsPtr->frameContentSize==0, it is ambiguous: the frame might actually be a Zstd encoded frame with no content.
+           For purposes of decompression, it is valid in both cases to skip the frame using
+           ZSTD_findFrameCompressedSize to find its size in bytes.
   It also returns Frame Size as fparamsPtr->frameContentSize.
 */