crc32

Standard CRC-32 algorithm implementation in JS (for the browser and nodejs). Emphasis on correctness and performance.

Installation

In nodejs:

npm install crc-32

In the browser:

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

The browser exposes a variable CRC32

Usage

• CRC32.buf(byte array or buffer) assumes the argument is a set of 8 bit unsigned integers (e.g. nodejs Buffer or simple array of ints)

• CRC32.bstr(binary string) interprets the argument as a binary string where the i-th byte is str.charCodeAt(i)

• CRC32.str(string) interprets the argument as a standard JS string

Testing

make test will run the nodejs-based test. To run the in-browser tests, run a local server and go to the ctest directory. To update the browser artifacts, run make ctest.

Performance

make perf will run algorithmic performance tests (which should justify certain decisions in the code).

make perf-all compares the performance of various crc-32 algorithms that implement the correct form (note that the SSE intrinsic is designed for the CRC32C checksum and uses a different polynomial).

Unexpected code patterns were based on performance testing in node and browser:

• Loop unrolling helps!

In the future ...

• Specifying an arbitrary initial CRC value

• Supporting different polynomials (e.g. CRC32C)

License

Please consult the attached LICENSE file for details. All rights not explicitly granted by the Apache 2.0 license are reserved by the Original Author.