RosettaCodeData/Task/Variable-length-quantity/Julia/variable-length-quantity.julia

using Printf

mutable struct VLQ
    quant::Vector{UInt8}
end

function VLQ(n::T) where T <: Integer
    quant = UInt8.(digits(n, 128))
    @inbounds for i in 2:length(quant) quant[i] |= 0x80 end
    VLQ(reverse(quant))
end

import Base.UInt64
function Base.UInt64(vlq::VLQ)
    quant = reverse(vlq.quant)
    n = shift!(quant)
    p = one(UInt64)
    for i in quant
        p *= 0x80
        n += p * ( i & 0x7f)
    end
    return n
end

const test = [0x00200000, 0x001fffff, 0x00000000, 0x0000007f,
              0x00000080, 0x00002000, 0x00003fff, 0x00004000,
              0x08000000, 0x0fffffff]

for i in test
    vlq = VLQ(i)
    j = UInt(vlq)
    @printf "0x%-8x => [%-25s] => 0x%x\n" i join(("0x" * hex(r, 2) for r in vlq.quant), ", ") j
end