encode and decode base256 encoding as gnu-tar does (supported range is -9007199254740991 to 9007199254740991).

npm install base-256 

It's a variable length encoding.

const{ encode, decode }=require('base-256')constbuf=newBuffer(12)encode(buf,2147483647)// buf here is <Buffer 80 7f ff ff ffconstdecodedValue=decode(buf)// decodedValue is 2147483647

base256.encode(buffer, num) Pass a buffer and the number that needs to be encoded. The number will be encoded into that buffer.

base256.decode(buf, [offset]) Decode a number from a buffer. If an offset is passed as the second argument the buf should be decoded at that byte offset. The byte offset defaults to 0.

• Throws TypeError if the input yields a number that is out of range (-9007199254740991 to 9007199254740991).
• Throws TypeError if the input is of not correct type.
• Throws TypeError if the output of decoded value of encoded buffer goes out of range -9007199254740991 to 9007199254740735.

MIT