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

using Printf

mutable struct VLQ
	quant::Vector{UInt8}
end

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

import Base.UInt64
function Base.UInt64(vlq::VLQ)
	quant = reverse(vlq.quant)
	n = popfirst!(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" * string(r, base = 16, pad = 2) for r in vlq.quant), ", ") j
end