How to turn binary into characters and viceversa

[Darlex]

How can I turn an array like [1,1,0,1,0,1] into a character? And how do I turn it back into an bit array like that one I already showed?
Is there an "easy" way to do it or do I need to do some LuaJIT trickery?

[zorg]

For one, you mean {1,1,0,1,0,1}, note the brackets; second, assuming that is a binary string, you can do this:

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string.byte(tonumber(table.concat{1,1,0,1,0,1}, 2))

Be aware that this isn't completely UTF-8 compatible, since it just returns 8-bit characters.

[ivan]

Beautiful solution by zorg.
My only concern would be the maximum number size that "tonumber" can handle. It will probably work fine for the 0-255 range.
A "safer" solution would be to iterate the table.

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local sum = 0
  for i = 1, #bin do
  sum = sum + bin[i]*math.pow(2, i - 1)
end
local byte = string.byte(sum)

You may have to reverse the table if the number is big or little endian.

[Darlex]

Woah thanks zorg and ivan! These are wonderful solutions! But how can I do the opposite? Like turning a character into a binary array?

[grump]

For 8-bit character bytes:

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local bits = {}
for i = 1, 8 do
	bits[i] = bit.band(byte, 2^(8-i)) > 0 and 1 or 0
end

Or for any number of bits:

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local bits = {}
local nbits = math.ceil(math.log(val) / math.log(2))
for i = 1, nbits do
	bits[i] = bit.band(val, 2^(nbits-i)) > 0 and 1 or 0
end

[zorg]

you might need to include the bit library to use those functions though... maybe; i usually do, but it might not be necessary; if it errors, you'll know anyway

[Darlex]

you might need to include the bit library to use those functions though... maybe; i usually do, but it might not be necessary; if it errors, you'll know anyway

Sorry for being an absolute noob in this lua* (jit/ffi/etc) stuff, where can i get some info?

[zorg]

luajit's own website, but it's not needed for this thing, you can just

Code: Select all

bit = require 'bit'

and it'll definitely work.

[Darlex]

luajit's own website, but it's not needed for this thing, you can just

Code: Select all

bit = require 'bit'

and it'll definitely work.

Thanks Zorg!