Re: manipulating bits not bytes-Enthusiasts level question

[Vaughan McAlley <vaughan@...>]

On 4 September 2010 23:15, Patrick Mc(avery
<spell_gooder_now@spellingbeewinnars.org> wrote:
>bin_all = bin:read("*all")

This should be
bin_all = bin:read("*a")

"*all" probably triggers one line's worth instead of the whole file

> Is there also a way to convert binary to hex in pure Lua, I know Mike Pall
> has a great library but it is there a way to do this in pure Lua?
>
> Is there also a way to read one bit? read(1) is one byte, is there a way to
> read one bit?
>
> Thanks for reading-Patrick

If you have a fair bit of memory to spare:

local scratch = {}
local bins = setmetatable({}, { __index = function(t, c)
    local highbit = 128
    c = string.byte(c)
    for i = 1, 8 do
        if c >= highbit then
            scratch[i] = "1"
            c = c % highbit
        else
            scratch[i] = "0"
        end
        highbit = highbit / 2
    end
    local result = table.concat(scratch)
    t[c] = result
    return result
end })


local BinToHex = function(bin)
    return string.gsub(bin, "[01][01][01][01]", function(b)
        return string.format("%1x", tonumber(b, 2))
    end)
end

local AsciiToBin = function(a)
    return string.gsub(a, ".", bins)
end

print(BinToHex("01110100 00001111 11010010"))
--> 74 0f d2

a = string.char(255, 155, 55, 0)

b = AsciiToBin(a)
print(b)
--> 11111111100110110011011100000000
-- (works on long strings as well)


Vaughan