kequapp/dist/body/multipart/split-multipart.js

A minimal, zero-magic Node web framework built on native APIs

import Ex from "../../built-in/tools/ex.js";
import headerAttributes from "../../util/header-attributes.js";
const CR = 0x0d;
const LF = 0x0a;
export default function splitMultipart(body) {
    const contentType = body.headers['content-type'];
    if (!contentType?.startsWith('multipart/')) {
        throw Ex.BadRequest('Unable to process request', {
            contentType,
        });
    }
    const boundary = extractBoundary(contentType);
    const buffer = body.data;
    const result = [];
    let headers = {};
    let i = findNextLine(buffer, buffer.indexOf(boundary, 0));
    function addHeader(nextLine) {
        const line = buffer.slice(i, nextLine).toString();
        const parts = line.split(':');
        const key = parts[0].trim().toLowerCase();
        const value = parts[1]?.trim();
        if (key && value)
            headers[key] = value;
    }
    function addPart(nextBoundary) {
        const dataEnd = nextBoundary - (buffer[nextBoundary - 2] === CR ? 2 : 1);
        result.push({
            headers,
            data: buffer.slice(i, dataEnd),
        });
        headers = {};
    }
    while (i > -1) {
        // until two new lines
        while (i > -1 && buffer[i] !== CR && buffer[i] !== LF) {
            const nextLine = findNextLine(buffer, i);
            if (nextLine > -1)
                addHeader(nextLine);
            i = nextLine;
        }
        if (i < 0)
            break;
        i += buffer[i] === CR ? 2 : 1;
        if (i >= buffer.length)
            break;
        // data start
        const nextBoundary = buffer.indexOf(boundary, i);
        if (nextBoundary < 0)
            break;
        addPart(nextBoundary);
        i = findNextLine(buffer, nextBoundary);
    }
    return result;
}
function extractBoundary(contentType) {
    const boundary = headerAttributes(contentType).boundary;
    if (!boundary) {
        throw Ex.BadRequest('Multipart request requires boundary attribute', {
            contentType,
        });
    }
    return `--${boundary}`;
}
function findNextLine(buffer, from) {
    const i = buffer.indexOf(LF, from) + 1;
    if (i < 1 || i >= buffer.length)
        return -1;
    return i;
}