Add formatting of bytes into the best unit of measurement

tests/core/Makefile

@@ -57,3 +57,6 @@ c_libc_test:
 
 net_test:
 	$(ODIN) run net -out:test_core_net
+
+fmt_test:
+	$(ODIN) run fmt -out:test_core_fmt

tests/core/fmt/test_core_fmt.odin

@@ -0,0 +1,59 @@
+package test_core_fmt
+
+import "core:fmt"
+import "core:os"
+import "core:testing"
+import "core:mem"
+
+TEST_count := 0
+TEST_fail  := 0
+
+when ODIN_TEST {
+	expect  :: testing.expect
+	log     :: testing.log
+} else {
+	expect  :: proc(t: ^testing.T, condition: bool, message: string, loc := #caller_location) {
+		TEST_count += 1
+		if !condition {
+			TEST_fail += 1
+			fmt.printf("[%v] %v\n", loc, message)
+			return
+		}
+	}
+	log     :: proc(t: ^testing.T, v: any, loc := #caller_location) {
+		fmt.printf("[%v] ", loc)
+		fmt.printf("log: %v\n", v)
+	}
+}
+
+main :: proc() {
+	t := testing.T{}
+	test_fmt_memory(&t)
+
+	fmt.printf("%v/%v tests successful.\n", TEST_count - TEST_fail, TEST_count)
+	if TEST_fail > 0 {
+		os.exit(1)
+	}
+}
+
+test_fmt_memory :: proc(t: ^testing.T) {
+	check :: proc(t: ^testing.T, exp: string, format: string, args: ..any, loc := #caller_location) {
+		got := fmt.tprintf(format, ..args)
+		expect(t, got == exp, fmt.tprintf("(%q, %v): %q != %q", format, args, got, exp), loc)
+	}
+
+	check(t, "5b",       "%m",    5)
+	check(t, "5B",       "%M",    5)
+	check(t, "-5B",      "%M",    -5)
+	check(t, "3.00kb",   "%m",    mem.Kilobyte * 3)
+	check(t, "3kb",      "%.0m",  mem.Kilobyte * 3)
+	check(t, "3KB",      "%.0M",  mem.Kilobyte * 3)
+	check(t, "3.000 mb", "%#.3m", mem.Megabyte * 3)
+	check(t, "3.50 gb",  "%#m",   u32(mem.Gigabyte * 3.5))
+	check(t, "001tb",    "%5.0m", mem.Terabyte)
+	check(t, "-001tb",   "%5.0m", -mem.Terabyte)
+	check(t, "2.50 pb",  "%#5.m", uint(mem.Petabyte * 2.5))
+	check(t, "1.00 EB",  "%#M",   mem.Exabyte)
+	check(t, "255 B",    "%#M",   u8(255))
+	check(t, "0b",       "%m",    u8(0))
+}