crc-32

Because the library returns signed 32-bit integers for performance, you may need to convert them to unsigned integers or hex strings using standard JS operators.

• To Unsigned 32-bit: Use the unsigned right shift operator >>> 0.
• To Hex String: Use .toString(16) on the unsigned result.
• To Signed 32-bit: Use the bitwise OR operator | 0.

// Convert signed to unsigned
CRC32.str("SheetJS") >>> 0                      // 2647669026

// Convert unsigned to hex
(CRC32.str("SheetJS") >>> 0).toString(16)         // "9dd03922"

// Convert unsigned back to signed
(2647669026 | 0)                                // -1647298270

Load the script directly via a <script> tag. The script exposes a global CRC32 variable.

Note: The script may attempt to manipulate module.exports if it detects a module environment. To prevent this behavior, define the environment variable DO_NOT_EXPORT_CRC before loading the script.

<script src="crc32.js"></script>

Install the crc-32 package using npm from the SheetJS CDN:

$ npm i --save https://cdn.sheetjs.com/crc-32-latest/crc-32-latest.tgz

1. Explicitly pass seed 0: While the seed is optional, passing 0 explicitly is recommended for performance.
2. Node.js Buffer optimization: In NodeJS, it is often faster to convert binary strings to Buffers using Buffer.from(bstr, "binary") before calling .buf() rather than using .bstr() directly.

/* Frequently slower in NodeJS */
crc32 = CRC32.bstr(bstr, 0);

/* Frequently faster in NodeJS */
crc32 = CRC32.buf(Buffer.from(bstr, "binary"), 0);

You can use require for CommonJS or import for ESM modules.

CommonJS:

var CRC32 = require("crc-32");

ESM:

import { bstr, buf, str } from "crc-32";

The crc32 command-line tool calculates CRC32 checksums for files or data piped via stdin. By default, it uses the standard CRC32 algorithm and outputs a signed integer. You can specify different algorithms (like CRC32C), custom seeds for rolling CRCs, and various output formats (hex, unsigned, etc.).

To read from standard input (stdin), use - as the filename or pipe data directly into the command.

# Calculate checksum for a file
crc32 myfile.txt

# Calculate checksum for piped data
echo "hello" | crc32

# Use CRC32C (Castagnoli) and output in uppercase hex
echo "hello" | crc32 -c -X

The crc32 command-line tool allows you to compute CRC32 or CRC32C checksums for files or data piped from stdin. By default, it outputs the result as a signed integer.

To read from standard input (stdin), use - as the filename or pipe data directly into the command.

Usage:

# Compute checksum for a file
crc32 [options] [filename]

# Compute checksum for piped data
cat file.txt | crc32

For CRC32C calculations, use the crc-32/crc32c entry point.

NodeJS/Bundler (CommonJS):

var CRC32C = require("crc-32/crc32c");

NodeJS/Bundler (ESM):

import { bstr, buf, str } from "crc-32/crc32c";

Browser: Load crc32c.js directly; it exposes a global CRC32C variable. Use DO_NOT_EXPORT_CRC to prevent module.exports manipulation.

Use CRC32C.buf(B, [seed]) to calculate the CRC-32C (Castagnoli) checksum of a buffer (such as a Uint8Array). This method is optimized for performance using a slice-by-16 algorithm.

• B: The input buffer (e.g., Uint8Array).
• seed (optional): An initial seed value for the calculation.

const CRC32C = require('./crc32c.js');

const data = new Uint8Array([0x01, 0x02, 0x03, 0x04]);
const checksum = CRC32C.buf(data);
console.log(checksum);

Use CRC32C.bstr(bstr, [seed]) to calculate the CRC-32C checksum of a binary string (where each character represents a single byte).

• bstr: The input binary string.
• seed (optional): An initial seed value for the calculation.

const CRC32C = require('./crc32c.js');

const bstr = "\x01\x02\x03\x04";
const checksum = CRC32C.bstr(bstr);
console.log(checksum);