From b077e2979c4ec21173e0ffa20ab7ee0c750a3ddc Mon Sep 17 00:00:00 2001
From: Andrew Kelley <andrew@ziglang.org>
Date: Sun, 6 Jul 2025 19:41:36 -0700
Subject: [PATCH] std.io.Reader: fix peekByte

---
 lib/std/io/Reader.zig | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/lib/std/io/Reader.zig b/lib/std/io/Reader.zig
index 914f27d3ef..f9abb2dd4d 100644
--- a/lib/std/io/Reader.zig
+++ b/lib/std/io/Reader.zig
@@ -1060,11 +1060,12 @@ pub fn fillMore(r: *Reader) Error!void {
 pub fn peekByte(r: *Reader) Error!u8 {
     const buffer = r.buffer[0..r.end];
     const seek = r.seek;
-    if (seek >= buffer.len) {
-        @branchHint(.unlikely);
-        try fill(r, 1);
+    if (seek < buffer.len) {
+        @branchHint(.likely);
+        return buffer[seek];
     }
-    return buffer[seek];
+    try fill(r, 1);
+    return r.buffer[r.seek];
 }
 
 /// Reads 1 byte from the stream or returns `error.EndOfStream`.