@thi.ng/server/utils/multipart.js

Minimal HTTP server with declarative routing, static file serving and freely extensible via pre/post interceptors

import { findSequence } from "@thi.ng/arrays";
import { illegalArgs } from "@thi.ng/errors";
const DECODER = new TextDecoder();
const parseRequestMultipartData = (req) => {
  const ctype = req.headers["content-type"];
  if (!ctype) illegalArgs("missing content-type");
  const boundary = /boundary=([a-z0-9-]+)/i.exec(ctype);
  if (!boundary) illegalArgs("missing boundary");
  return parseMultipartData(req, boundary[1]);
};
async function* parseMultipartData(req, boundary) {
  const parser = chunkParser(boundary);
  for await (let chunk of req) yield* parser(chunk);
}
const chunkParser = (boundary) => {
  const boundaryBytes = new TextEncoder().encode(boundary);
  let buf = new Uint8Array(0);
  let from = 0;
  return function* (chunk) {
    const $buf = new Uint8Array(buf.length + chunk.length);
    $buf.set(buf);
    $buf.set(chunk, buf.length);
    buf = $buf;
    while (buf.length) {
      const idx = findSequence(buf, boundaryBytes, from);
      if (idx < 0) {
        from = Math.max(buf.length - boundaryBytes.length + 1, 0);
        return;
      }
      if (idx >= 4) {
        yield parsePart(buf.slice(2, idx - 4));
      }
      buf = buf.slice(idx + boundaryBytes.length);
      from = 0;
    }
  };
};
const MPART_SEP = [13, 10, 13, 10];
const parsePart = (buf) => {
  const idx = findSequence(buf, MPART_SEP);
  if (idx < 0) illegalArgs("invalid multipart data");
  const headers = DECODER.decode(buf.slice(0, idx)).split("\r\n").reduce((acc, x) => {
    const idx2 = x.indexOf(":");
    let key = x.substring(0, idx2).toLowerCase();
    let val = x.substring(idx2 + 1).trim();
    if (key === "content-disposition") {
      const name = /name="([a-z0-9_.-]{1,64})"/i.exec(val);
      if (name) acc["name"] = name[1];
      const filename = /filename="([a-z0-9_.+\-~@ ()\[\]]{1,128})"/i.exec(val);
      if (filename) acc["filename"] = filename[1];
    }
    acc[key] = val;
    return acc;
  }, {});
  const body = buf.slice(idx + 4);
  return headers["content-type"] ? { headers, body } : { headers, body: DECODER.decode(body) };
};
export {
  chunkParser,
  parseMultipartData,
  parsePart,
  parseRequestMultipartData
};