cl-leb128

This small library encodes and decodes signed and unsigned leb128 numbers in Common Lisp.

It should be fast, (with the exception of the encode-signed operation, which has to do a data copy, and use a non-simple array, so lookup cost is incurred), as simple-array are used for the storage of the numbers, and it is iterative, with binary arithmetic used where possible.

API

(encode-signed i)

Returns a (simple-array (unsigned-byte 8)) with the leb128 encoding of i.

(decode-signed in &key (start 0))

Returns an integer decoded from in. in can either be a (array (unsigned-byte 8)), or a stream of values (unsigned-byte 8).

If start is supplied and a stream passed in, start number of bytes will be discarded from the input stream.

Returns two values, the decoded integer, as well as the number of bytes consumed.

(encode-unsigned i)

Works nearly identically to previously, but only accepts unsigned-byte numbers.

(decode-unsigned in &key (start 0))

Works nearly identically to decode-signed, returns two values as well, and takes the same inputs.