@ckeditor/ckeditor5-utils/src/crc32.js

Miscellaneous utilities used by CKEditor 5.

/**
 * @license Copyright (c) 2003-2025, CKSource Holding sp. z o.o. All rights reserved.
 * For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-licensing-options
 */
/**
 * @module utils/crc32
 */
/**
 * Generates a CRC lookup table.
 * This function creates and returns a 256-element array of pre-computed CRC values for quick CRC calculation.
 * It uses the polynomial 0xEDB88320 to compute each value in the loop, optimizing future CRC calculations.
 */
function makeCrcTable() {
    const crcTable = [];
    for (let n = 0; n < 256; n++) {
        let c = n;
        for (let k = 0; k < 8; k++) {
            if (c & 1) {
                c = 0xEDB88320 ^ (c >>> 1);
            }
            else {
                c = c >>> 1;
            }
        }
        crcTable[n] = c;
    }
    return crcTable;
}
/**
 * Calculates CRC-32 checksum for a given inputData to verify the integrity of data.
 *
 * @param inputData Accepts a single value (string, number, boolean), an array of strings, or an array of all of the above types.
 * Non-string values are converted to strings before calculating the checksum.
 * The checksum calculation is based on the concatenated string representation of the input values:
 * * `crc32('foo')` is equivalent to `crc32(['foo'])`
 * * `crc32(123)` is equivalent to `crc32(['123'])`
 * * `crc32(true)` is equivalent to `crc32(['true'])`
 * * `crc32(['foo', 123, true])` produces the same result as `crc32('foo123true')`
 * * Nested arrays of strings are flattened, so `crc32([['foo', 'bar'], 'baz'])` is equivalent to `crc32(['foobar', 'baz'])`
 *
 * @returns The CRC-32 checksum, returned as a hexadecimal string.
 */
export default function crc32(inputData) {
    const dataArray = Array.isArray(inputData) ? inputData : [inputData];
    const crcTable = makeCrcTable();
    let crc = 0 ^ (-1);
    // Convert data to a single string.
    const dataString = dataArray.map(item => {
        if (Array.isArray(item)) {
            return item.join('');
        }
        return String(item);
    }).join('');
    // Calculate the CRC for the resulting string.
    for (let i = 0; i < dataString.length; i++) {
        const byte = dataString.charCodeAt(i);
        crc = (crc >>> 8) ^ crcTable[(crc ^ byte) & 0xFF];
    }
    crc = (crc ^ (-1)) >>> 0; // Force unsigned integer.
    return crc.toString(16).padStart(8, '0');
}