Commit efd227eca2e2013b4e540ab2ba44664668a5253b | zig

author	Ryan Liptak <squeek502@hotmail.com> 2026-08-19 17:42:45-07:00
committer	Ryan Liptak <squeek502@hotmail.com> 2026-08-20 08:29:34+02:00
log	efd227eca2e2013b4e540ab2ba44664668a5253b
tree	9fe50c3ea6d6e86b3ddffa7508b6a96fd35b2d18
parent	7988f79528e2105a83bc00b91866b639b181dd51

File.Reader.seekBy: Fix erroneously tossing the buffer in streaming mode

The discard already handles updating the state, so the toss was redundant in the best case and would erroneously drop data in the worst case.

Closes #36568

2 files changed, 9 insertions(+), 4 deletions(-)

lib
- std
  - Io
    File
    Reader.zig
  - fs
    test.zig

lib/std/Io/File/Reader.zig-1

...	...	@@ -154,7 +154,6 @@ pub fn seekBy(r: *Reader, offset: i64) SeekError!void {
154	154	return err;
155	155	};
156	156	}
157		r.interface.tossBuffered();
158	157	},
159	158	.failure => return r.seek_err.?,
160	159	}

lib/std/fs/test.zig+9-3

...	...	@@ -2409,13 +2409,19 @@ test "seekBy" {
2409	2409	try tmp_dir.dir.writeFile(io, .{ .sub_path = "blah.txt", .data = "let's test seekBy" });
2410	2410	const f = try tmp_dir.dir.openFile(io, "blah.txt", .{ .mode = .read_only });
2411	2411	defer f.close(io);
2412		var reader = f.readerStreaming(io, &.{});
	2412	var buf: [10]u8 = undefined;
	2413	var reader = f.readerStreaming(io, &buf);
	2414	// Seek without any buffered data
	2415	try reader.seekBy(2);
	2416
	2417	// Seek when the buffered data is sufficient to satisfy the seek amount
	2418	try reader.interface.fill(2);
2413	2419	try reader.seekBy(2);
2414	2420
2415	2421	var buffer: [20]u8 = undefined;
2416	2422	const n = try reader.interface.readSliceShort(&buffer);
2417		try expectEqual(15, n);
2418		try expectEqualStrings("t's test seekBy", buffer[0..15]);
	2423	try expectEqual(13, n);
	2424	try expectEqualStrings("s test seekBy", buffer[0..n]);
2419	2425	}
2420	2426
2421	2427	test "seekTo flushes buffered data" {