multidimensional bitmaps in Lua

bitmap_lib.lua

#!/usr/bin/env lua5.4

--[[
  This file is licensed under the license `CC BY-NC-ND 4.0`, visit "https://creativecommons.org/licenses/by-nc-nd/4.0/" for additional information.
  author: wfrsk @ github.com  
]]

local INTEGER_SIZE <const> = string.packsize( "j" ) * 8

local function make_bitmap( x_bounds )
  local integers_required = math.ceil( x_bounds / INTEGER_SIZE )

  local internal_bitmap, external_adapter do
    internal_bitmap = { } do
      for index = 1, integers_required do
        internal_bitmap[ index ] = 0
      end
    end

    local function index_routine( _, bitspace_index )
      assert( type( bitspace_index ) == "number", "index must be an integer" )

      local integer_index, bit_index = math.ceil( bitspace_index / INTEGER_SIZE ), bitspace_index % INTEGER_SIZE

      return assert( internal_bitmap[ integer_index ], "index given out of bounds for bitmap" ) & ( 1 << ( bit_index - 1 ) )
    end

    local function newindex_routine( _, bitspace_index, new_value )
      assert( type( bitspace_index ) == "number", "index must be an integer" )

      local integer_index, bit_index = math.ceil( bitspace_index / INTEGER_SIZE ), bitspace_index % INTEGER_SIZE

      internal_bitmap[ integer_index ] = ( new_value & 1 ) == 1 and assert( internal_bitmap[ integer_index ], "index given out of bounds for bitmap" ) | ( 1 << ( bit_index - 1 ) ) or assert( internal_bitmap[ integer_index ], "index given out of bounds for bitmap" ) & ~( 1 << ( bit_index - 1 ) )
    end

    external_adapter = setmetatable( {  }, { __index = index_routine, __newindex = newindex_routine } )
  end

  return external_adapter
end

local function make_bitmap_2d( x_bounds, y_bounds )
  local bidimensional_bitmap = { } do
    for index = 1, x_bounds do
      bidimensional_bitmap[ index ] = make_bitmap( y_bounds )
    end
  end

  return bidimensional_bitmap
end

local function make_bitmap_3d( x_bounds, y_bounds, z_bounds )
  local tridimensional_bitmap = { } do
    for index = 1, x_bounds do
      tridimensional_bitmap[ index ] = make_bitmap_2d( y_bounds, z_bounds )
    end
  end

  return tridimensional_bitmap
end

return { make_bitmap = make_bitmap, make_bitmap_2d = make_bitmap_2d, make_bitmap_3d = make_bitmap_3d }