@jsreport/node-signpdf/src/helpers/pdfkit/pdfobject.js

Simple signing of PDFs in node.

/*
PDFObject by Devon Govett used below.
The class is part of pdfkit. See https://github.com/foliojs/pdfkit
LICENSE: MIT. Included in this folder.
Modifications may have been applied for the purposes of node-signpdf.
*/

import PDFAbstractReference from './abstract_reference';
/*
PDFObject - converts JavaScript types into their corresponding PDF types.
By Devon Govett
*/

const pad = (str, length) => (Array(length + 1).join('0') + str).slice(-length);

const escapableRe = /[\n\r\t\b\f()\\]/g;
const escapable = {
    '\n': '\\n',
    '\r': '\\r',
    '\t': '\\t',
    '\b': '\\b',
    '\f': '\\f',
    '\\': '\\\\',
    '(': '\\(',
    ')': '\\)',
};

// Convert little endian UTF-16 to big endian
const swapBytes = (buff) => buff.swap16();

export default class PDFObject {
    static convert(object, encryptFn = null) {
    // String literals are converted to the PDF name type
        if (typeof object === 'string') {
            return `/${object}`;

            // String objects are converted to PDF strings (UTF-16)
        } if (object instanceof String) {
            let string = object;
            // Detect if this is a unicode string
            let isUnicode = false;
            for (let i = 0, end = string.length; i < end; i += 1) {
                if (string.charCodeAt(i) > 0x7f) {
                    isUnicode = true;
                    break;
                }
            }

            // If so, encode it as big endian UTF-16
            let stringBuffer;
            if (isUnicode) {
                stringBuffer = swapBytes(Buffer.from(`\ufeff${string}`, 'utf16le'));
            } else {
                stringBuffer = Buffer.from(string, 'ascii');
            }

            // Encrypt the string when necessary
            if (encryptFn) {
                string = encryptFn(stringBuffer).toString('binary');
            } else {
                string = stringBuffer.toString('binary');
            }

            // Escape characters as required by the spec
            string = string.replace(escapableRe, (c) => escapable[c]);

            return `(${string})`;

            // Buffers are converted to PDF hex strings
        } if (Buffer.isBuffer(object)) {
            return `<${object.toString('hex')}>`;
        } if (object instanceof PDFAbstractReference) {
            return object.toString();
        } if (object instanceof Date) {
            let string = `D:${pad(object.getUTCFullYear(), 4)}${pad(object.getUTCMonth() + 1, 2)}${pad(object.getUTCDate(), 2)}${pad(object.getUTCHours(), 2)}${pad(object.getUTCMinutes(), 2)}${pad(object.getUTCSeconds(), 2)}Z`;

            // Encrypt the string when necessary
            if (encryptFn) {
                string = encryptFn(Buffer.from(string, 'ascii')).toString('binary');

                // Escape characters as required by the spec
                string = string.replace(escapableRe, (c) => escapable[c]);
            }

            return `(${string})`;
        } if (Array.isArray(object)) {
            const items = object.map((e) => PDFObject.convert(e, encryptFn)).join(' ');
            return `[${items}]`;
        } if ({}.toString.call(object) === '[object Object]') {
            const out = ['<<'];
            let streamData;

            // @todo this can probably be refactored into a reduce
            Object.entries(object).forEach(([key, val]) => {
                let checkedValue = '';

                if (val.toString().indexOf('<<') !== -1) {
                    checkedValue = val;
                } else {
                    checkedValue = PDFObject.convert(val, encryptFn);
                }

                if (key === 'stream') {
                    streamData = `${key}\n${val}\nendstream`;
                } else {
                    out.push(`/${key} ${checkedValue}`);
                }
            });
            out.push('>>');

            if (streamData) {
                out.push(streamData);
            }
            return out.join('\n');
        } if (typeof object === 'number') {
            return PDFObject.number(object);
        }
        return `${object}`;
    }

    static number(n) {
        if (n > -1e21 && n < 1e21) {
            return Math.round(n * 1e6) / 1e6;
        }

        throw new Error(`unsupported number: ${n}`);
    }
}