Fixed String Test

1import { describe, expect, it } from "vitest";
2import { query } from "./clickhouse.js";
3import { NeedMoreData, Cursor } from "../src/readers/core.js";
4import { readFixedString } from "../src/readers/strings.js";
5
6async function reader(expr: string): Promise<Cursor> {
7  return new Cursor(await query(`SELECT ${expr} FORMAT RowBinary`));
8}
9
10describe("readFixedString", () => {
11  it("decodes a full-width value (no padding)", async () => {
12    const r = await reader("toFixedString('abcd', 4)");
13    expect(readFixedString(4)(r)).toBe("abcd");
14    expect(r.pos).toBe(4);
15  });
16
17  // Shorter content is right-padded with NUL bytes, which are preserved.
18  it("preserves trailing NUL padding", async () => {
19    expect(readFixedString(4)(await reader("toFixedString('ab', 4)"))).toBe(
20      "ab\x00\x00",
21    );
22  });
23
24  describe("advance() edge cases", () => {
25    it("throws NeedMoreData for every incomplete prefix (0 .. full.length-1)", async () => {
26      const full = await query(
27        "SELECT toFixedString('ab', 4) FORMAT RowBinary",
28      );
29      for (let len = 0; len < full.length; len++) {
30        const r = new Cursor(full.subarray(0, len));
31        let thrown: unknown;
32        try {
33          readFixedString(4)(r);
34        } catch (e) {
35          thrown = e;
36        }
37        expect(thrown, `prefix length ${len} of ${full.length}`).toBe(
38          NeedMoreData,
39        );
40      }
41    });
42  });
43});