varint

What is varint?

The varint npm package is used for encoding and decoding variable-length integers. It is particularly useful in scenarios where you need to efficiently store or transmit integers that can vary greatly in size, such as in network protocols or file formats.

What are varint's main functionalities?

Encoding Integers

This feature allows you to encode an integer into a variable-length format. The encoded result is an array of bytes.

const varint = require('varint');
const encoded = varint.encode(300); // [172, 2]
console.log(encoded);

Decoding Integers

This feature allows you to decode a variable-length encoded integer back into its original integer form.

const varint = require('varint');
const decoded = varint.decode([172, 2]); // 300
console.log(decoded);

Encoding Integers to Buffer

This feature allows you to encode an integer directly into a Buffer, which can be useful for more advanced use cases involving binary data.

const varint = require('varint');
const buffer = Buffer.alloc(10);
const bytesWritten = varint.encode(300, buffer, 0); // 2
console.log(buffer.slice(0, bytesWritten));

Decoding Integers from Buffer

This feature allows you to decode an integer from a Buffer, which is useful when working with binary data streams.

const varint = require('varint');
const buffer = Buffer.from([172, 2]);
const decoded = varint.decode(buffer); // 300
console.log(decoded);

Other packages similar to varint

protobufjs

protobufjs is a comprehensive library for working with Protocol Buffers, which includes functionality for encoding and decoding variable-length integers. It is more feature-rich compared to varint, offering schema definitions and more complex data structures.

msgpack-lite

msgpack-lite is a library for encoding and decoding data in the MessagePack format, which includes support for variable-length integers. It is similar to varint but also supports a wider range of data types and is optimized for performance.

leb128

leb128 is a library for encoding and decoding LEB128 (Little Endian Base 128) integers, which is another form of variable-length integer encoding. It is similar to varint but uses a different encoding scheme.

README

varint

encode whole numbers to an array of protobuf-style varint bytes and also decode them.

var varint = require('varint')

var bytes = varint.encode(300) // === [0xAC, 0x02]
varint.decode(bytes) // 300
varint.decode.bytes // 2 (the last decode() call required 2 bytes)

api

varint = require('varint')

varint.encode(num[, buffer=[], offset=0]) -> buffer

Encodes num into buffer starting at offset. returns buffer, with the encoded varint written into it. If buffer is not provided, it will default to a new array.

varint.encode.bytes will now be set to the number of bytes modified.

varint.decode(data[, offset=0]) -> number

decodes data, which can be either a buffer or array of integers, from position offset or default 0 and returns the decoded original integer.

Throws a RangeError when data does not represent a valid encoding.

varint.decode.bytes

if you also require the length (number of bytes) that were required to decode the integer you can access it via varint.decode.bytes. this is an integer property that will tell you the number of bytes that the last .decode() call had to use to decode.

varint.encode.bytes

similar to decode.bytes when encoding a number it can be useful to know how many bytes where written (especially if you pass an output array). you can access this via varint.encode.bytes which holds the number of bytes written in the last encode.

varint.encodingLength(num)

returns the number of bytes this number will be encoded as, up to a maximum of 8.

usage notes

If varint is passed a buffer that does not contain a valid end byte, then decode will throw RangeError, and decode.bytes will be set to 0. If you are reading from a streaming source, it's okay to pass an incomplete buffer into decode, detect this case, and then concatenate the next buffer.

License

MIT