body.mjs

Functions

Imports

It imports no other module of this repo. Imported by csp-report.mjs.

Source

1/**
2 * A request body read to a byte ceiling, counted as the chunks arrive. The declared Content-Length can be absent or
3 * understated, and `request.text()` holds the whole body in memory before any check can run, so neither is a cap.
4 *
5 * Over the ceiling is `null`, never a truncated body, so the caller answers 413 instead of parsing a fragment. A
6 * stream that fails mid-read THROWS: an empty body is no safe stand-in, because every caller parses what it gets.
7 */
8
9/**
10 * @param {{ body: ReadableStream<Uint8Array> | null }} source a Request, or anything with a body stream
11 * @param {number} max the ceiling in bytes
12 * @returns {Promise<Uint8Array | null>} the body (empty when there is none), or null when it is longer than `max`
13 */
14export async function readCappedBytes(source, max) {
15  if (!Number.isInteger(max) || max < 0) throw new RangeError(`the ceiling must be a whole number of bytes, got ${max}`);
16  if (!source.body) return new Uint8Array(0);
17  const reader = source.body.getReader();
18  /** @type {Uint8Array[]} */
19  const chunks = [];
20  let total = 0;
21  try {
22    for (;;) {
23      const { done, value } = await reader.read();
24      if (done) break;
25      if (!value) continue;
26      total += value.byteLength;
27      if (total > max) {
28        await reader.cancel().catch(() => {});
29        return null;
30      }
31      chunks.push(value);
32    }
33  } catch (error) {
34    throw new Error(`the body stream failed after ${total} bytes: ${error instanceof Error ? error.message : String(error)}`, { cause: error });
35  }
36  const joined = new Uint8Array(total);
37  let at = 0;
38  for (const chunk of chunks) {
39    joined.set(chunk, at);
40    at += chunk.byteLength;
41  }
42  return joined;
43}
44
45/**
46 * `readCappedBytes`, decoded as UTF-8: "" for no body, null when over the ceiling.
47 * @param {{ body: ReadableStream<Uint8Array> | null }} source
48 * @param {number} max
49 * @returns {Promise<string | null>}
50 */
51export async function readCapped(source, max) {
52  const bytes = await readCappedBytes(source, max);
53  return bytes === null ? null : new TextDecoder().decode(bytes);
54}