Module:GetIDEMASectors

Documentation for this module may be created at Module:GetIDEMASectors/doc

local p = {}

-- Returns the number of IDEMA sectors given a capacity in GB.
function p.getIDEMASectors(gbCapacity, sectorSize)
	-- If given one of the Advanced Format codes, convert it to a numerical sector size.
	if (sectorSize == "No" or sectorSize == "512n" or sectorSize == "512e") then
		sectorSize = 512
	elseif (sectorSize == "4Kn" or sectorSize == "4,096") then
		sectorSize = 4096
	else
		sectorSize = tonumber(sectorSize)
	end
	
	if (gbCapacity <= 8000) then
		-- http://www.idema.org/wp-content/downloads/2169.pdf
		gb50Less = gbCapacity - 50
	
		if (sectorSize == 512) then
			return math.floor(97696368 + (1953504 * gb50Less))
		elseif (sectorSize == 4096) then
			return math.floor(12212046 + (244188 * gb50Less))
		else
			error("getIDEMASectors: Sector size given was not 512 or 4096 (was " .. sectorSize .. ")")
		end
	else 
		-- https://members.snia.org/document/dl/25903
		gbCapacityInBytes = gbCapacity * 1000000000
		
		if (sectorSize == 512 or sectorSize == "512") then
			return p.sffCeiling(gbCapacityInBytes / 512, 2^21)
		elseif (sectorSize == 4096 or sectorSize == "4096" or sectorSize == "4,096") then
			return p.sffCeiling(gbCapacityInBytes / 4096, 2^18)
		-- @todo: Add SCSI Protection Information and non-512 sector size compatibility
		else
			error("getIDEMASectors: Sector size given was not 512 or 4096 (was " .. sectorSize .. ")")
		end
	end
end

-- Implements the SFF's pseudocode ceiling function.
-- https://stackoverflow.com/a/32106643
function p.sffCeiling(number, multiple)
	return (math.ceil(number / multiple) * multiple)	
end

-- Implements the SFF's pseudocode floor function.
function p.sffFloor(number, multiple)
	return (math.floor(number / multiple) * multiple)	
end

-- Main entry point for this module.
function p.invokeMain(frame)
	return p.getIDEMASectors(tonumber(frame.args[1]), frame.args[2])
end

return p