readUntilDelimiter*: read only if buffer not full

[scorphus]

This is one way I see #9594 being solved. I hope I didn't get it too far off. I'm more than happy making any changes (and learn in the process)

I decided to start with readUntilDelimiter and readUntilDelimiterOrEof and submit this as draft to collect early feedbacks — which are more than welcome 🙂 I'll continue to the other readUntilDelimiter* functions.

Happy to propose my first contribution to Zig! 🎉 Thanks to @SpexGuy for suggesting me this issue.

[SpexGuy]

Not all readers support seekBy. I think a better solution would be to avoid reading at all if the output buffer is full.

[scorphus]

Not all readers support seekBy. I think a better solution would be to avoid reading at all if the output buffer is full.

Yeah, it's so true that most streams don't support rewinding. #mybad

I actually thought about that a few iterations before. Without reading the next byte, how's it going to be able to stop and return what can be a full buffer?

[scorphus]

For instance:

test "Reader.readUntilDelimiter EndOfStream 2" {
    var buf: [4]u8 = undefined;
    const reader = std.io.fixedBufferStream("1234\n").reader();
    try std.testing.expectEqualStrings("1234", try reader.readUntilDelimiter(&buf, '\n'));
    try std.testing.expectError(error.EndOfStream, reader.readUntilDelimiter(&buf, '\n'));
}

[SpexGuy]

That test would no longer pass, the buffer would need to be at least 5 bytes long. An easy way to communicate that might be to say that the output buffer needs to contain (or be terminated by) the delimiter if one was found.

[scorphus]

Thanks, @SpexGuy! PR updated. I would appreciate reading from you again, while I write tests for the remaining readUntilDelimiter* and start checking namespaces that use them (e.g. std.net).

[SpexGuy]

Thanks for doing this work!

[scorphus]

You're welcome. I'm happy to contribute 🙂 And this is fun! It makes much sense after I thought about what you wrote. Thanks, @SpexGuy!

[SpexGuy]

Just noticed one more thing :)

[SpexGuy]

The documentation should be updated to say something like "The delimiter byte is written to the output buffer, but is not included in the returned slice."

[scorphus]

Oh yes, definitely! I'm only waiting until we have a resolute "new behavior" so I can update all those docs ;-)