Little Endian Base 128 (LEB128) encoding and decoding module for the Julia programming language
LEB128 or Little Endian Base 128 is a form of variable-length code compression used to store an arbitrarily large integer in a small number of bytes. There are 2 versions of LEB128: unsigned LEB128 and signed LEB128. The decoder must know whether the encoded value is unsigned LEB128 or signed LEB128.
At the Julia prompt, type:
julia> Pkg.add("LittleEndianBase128")
julia> using LittleEndianBase128
julia> x = rand(-100:100, 3, 3)
3×3 Array{Int64,2}:
-95 9 -76
-71 -2 60
43 57 14
julia> y = encode(x)
12-element Array{UInt8,1}:
0xbd
0x01
0x8d
0x01
0x56
0x12
0x03
0x72
0x97
0x01
0x78
0x1c
julia> z = reshape(decode(y, Int8), 3, 3)
3×3 Array{Int64,2}:
-95 9 -76
-71 -2 60
43 57 14
julia> z = reshape(decodesigned(y), 3, 3)
3×3 Array{Int64,2}:
-95 9 -76
-71 -2 60
43 57 14
julia> z = reshape(decode(y), 3, 3)
3×3 Array{UInt64,2}:
0x00000000000000bd 0x0000000000000012 0x0000000000000097
0x000000000000008d 0x0000000000000003 0x0000000000000078
0x0000000000000056 0x0000000000000072 0x000000000000001c
Note that the encoded array is 1-D because the length of each encoded element is not fixed, so a uniform array shaping is not possible. This is the tradeoff of getting a large compression factor. Consequently when decoding, you'll need to reshape the output back to the original shape, because no shape information is retained within the encoded data.
Also notice that the final decode command assumed that the output is unsigned, so it produced incorrect output. If you have encoded signed data that you wish to decode, then you need to call decodesigned or decode(::Array{UInt8,1}, ::DataType) with an appropriate signed data type passed in the second argument.
For help, file an issue on the bug tracker or email one of the authors. Third party help is welcome and can be contributed through pull requests.
David S. Smith, Dong Wang
This code comes with no warranty. Use at your own risk.