-- module for reading serialized lua bytecode

local bit=require('bit')

local HEADER_MAGIC = {27, string.byte('L'), string.byte('J')}
local HEADER_FLAG_STRIP = 0x02

local function read_uleb128(fp)
    local last_byte = false
    local res = 0
    local shift = 0
    -- the bytes are read from the LSB to the MSB
    while not last_byte do
        local uleb_byte = string.byte(fp:read(1))
        res = bit.bor(res, bit.lshift(bit.band(uleb_byte, 0x7f), shift))

        if bit.band(uleb_byte, 0x80) == 0 then
            last_byte = true
        end
    end
    return res
end

local function read_header(fp)
    local magic = { string.byte(fp:read(3), 1, 3) }
    local version = string.byte(fp:read(1))
    local flags = read_uleb128(fp)

    local name
    if bit.band(flags, HEADER_FLAG_STRIP) ~= 0 then
        name = ''
    else
        local nameLen = read_uleb128(fp)
        name = fp:read(nameLen)
    end

    return {
        magic = magic,
        version = version,
        flags = flags,
        name = name,
    }
end

local function read_proto(fp)
end

return {
    read_header = read_header,
    read_proto = read_proto,
}