From f6de3ec963e3a7d96cd4f6c72b0f076f0437c45d Mon Sep 17 00:00:00 2001
From: dweiller <4678790+dweiller@users.noreply.github.com>
Date: Fri, 3 Nov 2023 17:09:29 +1100
Subject: [PATCH] zstandard: fix incorrect RLE decompression into ring buffer

This reverts a change introduced in #17400 causing a bug when
decompressing an RLE block into a ring buffer.

RLE blocks contain only a single byte of data to copy into the output,
so attempting to copy a slice causes buffer overruns and incorrect
decompression.
---
 lib/std/compress/zstandard/decode/block.zig | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/lib/std/compress/zstandard/decode/block.zig b/lib/std/compress/zstandard/decode/block.zig
index 36837a6b53..ac8b756c17 100644
--- a/lib/std/compress/zstandard/decode/block.zig
+++ b/lib/std/compress/zstandard/decode/block.zig
@@ -721,7 +721,9 @@ pub fn decodeBlockRingBuffer(
         },
         .rle => {
             if (src.len < 1) return error.MalformedRleBlock;
-            dest.writeSliceAssumeCapacity(src[0..block_size]);
+            for (0..block_size) |_| {
+                dest.writeAssumeCapacity(src[0]);
+            }
             consumed_count.* += 1;
             decode_state.written_count += block_size;
             return block_size;