1 files changed, 80 insertions, 0 deletions
diff --git a/util/human/units.lua b/util/human/units.lua
new file mode 100644
index 00000000..af233e98
--- /dev/null
+++ b/util/human/units.lua
@@ -0,0 +1,80 @@
+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 or unpack; --luacheck: ignore 113
+
+if math_log(10, 10) ~= 1 then
+	-- Lua 5.1 COMPAT
+	local log10 = math.log10;
+	function math_log(n, base)
+		return log10(n) / log10(base);
+	end
+end
+
+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;
+};