From 618bf84e0d16070ac67a80b404041adb264c4952 Mon Sep 17 00:00:00 2001
From: Yoni Gilad <yonig@radcom.com>
Date: Thu, 17 Feb 2022 19:46:29 +0200
Subject: [PATCH] seekable_format: Prevent rereading frame when seeking forward

When decompressing a seekable file, if seeking forward within
a frame (by issuing multiple ZSTD_seekable_decompress calls
with a small gap between them), the frame will be unnecessarily
reread from the beginning. This patch makes it continue using
the current frame data and simply skip over the unneeded bytes.
---
 contrib/seekable_format/zstdseek_decompress.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/contrib/seekable_format/zstdseek_decompress.c b/contrib/seekable_format/zstdseek_decompress.c
index fbb2d4fe3..4fefc5f2e 100644
--- a/contrib/seekable_format/zstdseek_decompress.c
+++ b/contrib/seekable_format/zstdseek_decompress.c
@@ -493,7 +493,7 @@ size_t ZSTD_seekable_decompress(ZSTD_seekable* zs, void* dst, size_t len, unsign
     size_t srcBytesRead = 0;
     do {
         /* check if we can continue from a previous decompress job */
-        if (targetFrame != zs->curFrame || offset != zs->decompressedOffset) {
+        if (targetFrame != zs->curFrame || offset < zs->decompressedOffset) {
             zs->decompressedOffset = zs->seekTable.entries[targetFrame].dOffset;
             zs->curFrame = targetFrame;