function get_next_char(script)
    local c = script:readU8()
    if c >= 0x80 then c = (c - 0x80) + (script:readU8() * 128) end
    return c
end

function get_next_utf8(str)
    local ret = ""
    local n
    local b
    
    n = str:sub(1, 1)
    ret = ret .. n
    str = str:sub(2)
    b = n:byte()
    if b <= 0x7f then return ret, str end
    
    if b >= 0x80 and b <= 0xc1 then error("Wrong UTF-8 sequence.") end
    
    n = str:sub(1, 1)
    ret = ret .. n
    str = str:sub(2)
    if b <= 0xdf then return ret, str end

    n = str:sub(1, 1)
    ret = ret .. n
    str = str:sub(2)
    if b <= 0xef then return ret, str end

    n = str:sub(1, 1)
    ret = ret .. n
    str = str:sub(2)
    if b <= 0xf4 then return ret, str end
    
    error("Wrong UTF-8 sequence.")
end

function dump_special(script, code)
    if code == 0 then
        return "\n", "\n"
    elseif code == 1 then
        return "\n<new/>\n", "\n"
    elseif code == 2 then
        return "<pause>", ""
    elseif code == 3 then
        local speed = script:readU8()
        if speed == 255 then
            return '<rspd/>', ""
        else
            return '<st spd="' .. speed .. '"/>', ""
        end
    elseif code == 4 then
        return '<st clr="' .. script:readU8() .. '"/>', ""
    elseif code == 5 then
        return '<start/>', ""
    elseif code == 7 then
        local rep = script:readU8()
        if rep == 1 then
            return '<rrep/>', ""
        else
            return '<st rep="' .. rep ..'"/>', ""
        end
    elseif code == 8 then
        local siz = script:readU8()
        if siz == 1 then
            return '<rsiz/>', ""
        else
            return '<st siz="' .. siz ..'"/>', ""
        end
    elseif code == 14 then
        return '<var n="' .. script:readU8() .. '"/>', ""
    elseif code == 17 then
        local t, u
        t = script:readU8()
        u = script:readU8()
        return '<delay t="' .. t .. '" u="' .. u .. '">', ""
    elseif code == 18 then
        return "<ssync/>", ""
    elseif code == 19 then
        local arg1, arg2
        arg1 = script:readU8()
        arg2 = script:readU8()
        if arg1 == 255 and arg2 == 255 then
            return '<dport/>', ""
        else
            return '<port a1="' .. arg1 .. '" a2="' .. arg2 .. '"/>', ""
        end
    else
        local a1, a2
        if code == 3 or code == 4 or code == 7 or code == 8 or code == 14 then
            a1 = script:readU8()
            return '<u1 c="' .. code .. '" a="' .. a1 .. '"/>', ""
        elseif code == 6 or code == 12 or code == 19 then
            a1 = script:readU8()
            a2 = script:readU8()
            return '<u2 c="' .. code .. '" a1="' .. a1 .. '" a2="' .. a2 .. '"/>', ""
        else
            return '<uk c="' .. code .. '"/>', ""
        end
    end
    error "Should not end up there"
end

function dump_special2(script, code)
    if code == 0 then
        return "\n", "\n"
    elseif code == 1 then
        return "\n<new/>\n", "\n"
    elseif code == 2 then
        return "<pause>", ""
    else
        local a1, a2
        if code == 3 or code == 5 or code == 7 or code == 8 or code == 9 or code == 12 or code == 13 or code == 14 or code == 15 or code == 21 then
            a1 = script:readU8()
            return '<u1 c="' .. code .. '" a="' .. a1 .. '"/>', ""
        elseif code == 20 then
            a1 = script:readU8()
            a2 = script:readU8()
            return '<u2 c="' .. code .. '" a1="' .. a1 .. '" a2="' .. a2 .. '"/>', ""
        else
            return '<uk c="' .. code .. '"/>', ""
        end
    end
    error "Should not end up there"
end

function extract_char(script, lookup)
    local c = get_next_char(script)
    if c == 0 then return nil end
    
    if c >= 0x4000 then
        local code = c - 0x4000
        if second_style_script then
            return dump_special2(script, code)
        else
            return dump_special(script, code)
        end
    else
        local l = lookup[c]
        if not l and not sloppy_extract then error("Lookup failed for character " .. c) end
        if not l then
            return '<failed value="' .. c .. '"/>', ""
        else
            return l, l
        end
    end
    error "Should not end up there"
end

function get_txt_idx(txt)
    local sha1 = SHA1(txt)
    return all_sha1[sha1]
end

function add_txt_idx(txt)
    local idx
    idx = #all_txts + 1
    local sha1 = SHA1(txt)
    all_sha1[sha1] = idx
    all_txts[idx] = {
        sha1 = sha1,
        txt = txt,
    }
    if all_origins[idx] then error("Something's inconsistant") end
    all_origins[idx] = "" .. (current_file - 3610)
    return idx
end

function process_ptrs(ptrs_contents, ptr_begin, ptr_end)
    local r = {}
    
    for i = ptr_begin, ptr_end do
        local idx = get_txt_idx(ptrs_contents[i])
        if not idx then
            idx = add_txt_idx(ptrs_contents[i])
        else
            if not all_origins[idx] then error("Something's inconsistant") end
            all_origins[idx] = all_origins[idx] .. "," .. (current_file - 3610)
        end
        r[i] = idx
    end
    return r
end