File

util/human/units.lua @ 13107:9c4dc1e6d2c9

mod_http: Add way to retrieve internal URL instead of external This could be of help when configuring reverse proxies, as it is the internal URL the proxy must point at. Argument treated as an enum "internal" "external"(default) to allow for future extensibility.
author Kim Alvefur <zash@zash.se>
date Wed, 24 May 2023 14:43:45 +0200
parent 12589:39ae08180c81
line wrap: on
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local math_abs = math.abs;
local math_ceil = math.ceil;
local math_floor = math.floor;
local math_log = math.log;
local math_max = math.max;
local math_min = math.min;
local unpack = table.unpack;

local large = {
	"k", 1000,
	"M", 1000000,
	"G", 1000000000,
	"T", 1000000000000,
	"P", 1000000000000000,
	"E", 1000000000000000000,
	"Z", 1000000000000000000000,
	"Y", 1000000000000000000000000,
}
local small = {
	"m", 0.001,
	"μ", 0.000001,
	"n", 0.000000001,
	"p", 0.000000000001,
	"f", 0.000000000000001,
	"a", 0.000000000000000001,
	"z", 0.000000000000000000001,
	"y", 0.000000000000000000000001,
}

local binary = {
	"Ki", 2^10,
	"Mi", 2^20,
	"Gi", 2^30,
	"Ti", 2^40,
	"Pi", 2^50,
	"Ei", 2^60,
	"Zi", 2^70,
	"Yi", 2^80,
}

local function adjusted_unit(n, b)
	local round = math_floor;
	local prefixes = large;
	local logbase = 1000;
	if b == 'b' then
		prefixes = binary;
		logbase = 1024;
	elseif n < 1 then
		prefixes = small;
		round = math_ceil;
	end
	local m = math_max(0, math_min(8, round(math_abs(math_log(math_abs(n), logbase)))));
	local prefix, multiplier = unpack(prefixes, m * 2-1, m*2);
	return multiplier or 1, prefix;
end

-- n: number, the number to format
-- unit: string, the base unit
-- b: optional enum 'b', thousands base
local function format(n, unit, b) --> string
	local fmt = "%.3g %s%s";
	if n == 0 then
		return fmt:format(n, "", unit);
	end
	local multiplier, prefix = adjusted_unit(n, b);
	return fmt:format(n / multiplier, prefix or "", unit);
end

return {
	adjust = adjusted_unit;
	format = format;
};