Initial cut of timezones

core/time/timezone/tz_unix.odin

@@ -0,0 +1,85 @@
+#+build darwin, linux, freebsd, openbsd, netbsd
+#+private
+package timezone
+
+import "core:os"
+import "core:strings"
+import "core:path/filepath"
+import "core:time/datetime"
+
+local_tz_name :: proc(allocator := context.allocator) -> (name: string, success: bool) {
+	local_str, ok := os.lookup_env("TZ", allocator)
+	if !ok {
+		orig_localtime_path := "/etc/localtime"
+		path, err := os.absolute_path_from_relative(orig_localtime_path)
+		if err != nil {
+			// If we can't find /etc/localtime, fallback to UTC
+			if err == .ENOENT {
+				str, err2 := strings.clone("UTC", allocator)
+				if err2 != nil { return }
+				return str, true
+			}
+
+			return
+		}
+		defer delete(path)
+
+		// FreeBSD makes me sad.
+		if path == orig_localtime_path {
+			data := os.read_entire_file("/var/db/zoneinfo") or_return
+			return strings.trim_right_space(string(data)), true
+		}
+
+		// Looking for tz path (ex fmt: "UTC", "Etc/UTC" or "America/Los_Angeles")
+		path_dir, path_file := filepath.split(path)
+		if path_dir == "" {
+			return
+		}
+		upper_path_dir, upper_path_chunk := filepath.split(path_dir[:len(path_dir)-1])
+		if upper_path_dir == "" {
+			return
+		}
+
+		if strings.contains(upper_path_chunk, "zoneinfo") {
+			region_str, err := strings.clone(path_file, allocator)
+			if err != nil { return }
+			return region_str, true
+		} else {
+			region_str, err := filepath.join({upper_path_chunk, path_file}, allocator = allocator)
+			if err != nil { return }
+			return region_str, true
+		}
+	}
+
+	if local_str == "" {
+		str, err := strings.clone("UTC", allocator)
+		if err != nil { return }
+		return str, true
+	}
+
+	return local_str, true
+}
+
+_region_load :: proc(_reg_str: string, allocator := context.allocator) -> (out_reg: ^datetime.TZ_Region, success: bool) {
+	reg_str := _reg_str
+	if reg_str == "UTC" {
+		return nil, true
+	}
+
+	if reg_str == "local" {
+		local_name := local_tz_name(allocator) or_return
+		if local_name == "UTC" {
+			delete(local_name, allocator)
+			return nil, true
+		}
+
+		reg_str = local_name
+	}
+	defer if _reg_str == "local" { delete(reg_str, allocator) }
+
+	db_path := "/usr/share/zoneinfo"
+	region_path := filepath.join({db_path, reg_str}, allocator)
+	defer delete(region_path, allocator)
+
+	return load_tzif_file(region_path, reg_str, allocator)
+}