Improve clocks

There's a flaky performance test that I wanted to fix (1). This led to a couple
changes.

1 - Add timestamp() and milliTimestamp() to datetime.zig. Reduce some code
    duplication and use better clock_ids where available

2 - Change Performance API to use milliTimestamp and store a u64 instead of a
    f64. While the spec says a float, Firefox deals with u64 and implicit
    conversion is always available. Makes our APIs simpler.

(1) - https://github.com/lightpanda-io/browser/actions/runs/17313296490/job/49151366798#step:4:131

src/browser/console/console.zig

@@ -165,8 +165,7 @@ pub const Console = struct {
 };
 
 fn timestamp() u32 {
-    const ts = std.posix.clock_gettime(std.posix.CLOCK.MONOTONIC) catch unreachable;
-    return @intCast(ts.sec);
+    return @import("../../datetime.zig").timestamp();
 }
 
 var test_capture = TestCapture{};

src/browser/dom/performance.zig

@@ -23,6 +23,8 @@ const EventTarget = @import("../dom/event_target.zig").EventTarget;
 const Env = @import("../env.zig").Env;
 const Page = @import("../page.zig").Page;
 
+const milliTimestamp = @import("../../datetime.zig").milliTimestamp;
+
 pub const Interfaces = .{
     Performance,
     PerformanceEntry,
@@ -36,29 +38,27 @@ pub const Performance = struct {
     // Extend libdom event target for pure zig struct.
     base: parser.EventTargetTBase = parser.EventTargetTBase{ .internal_target_type = .performance },
 
-    time_origin: std.time.Timer,
+    time_origin: u64,
     // if (Window.crossOriginIsolated) -> Resolution in isolated contexts:       5 microseconds
     // else                            -> Resolution in non-isolated contexts: 100 microseconds
     const ms_resolution = 100;
 
-    fn limitedResolutionMs(nanoseconds: u64) f64 {
-        const elapsed_at_resolution = ((nanoseconds / std.time.ns_per_us) + ms_resolution / 2) / ms_resolution * ms_resolution;
-        const elapsed = @as(f64, @floatFromInt(elapsed_at_resolution));
-        return elapsed / @as(f64, std.time.us_per_ms);
-    }
-
-    pub fn get_timeOrigin(self: *const Performance) f64 {
-        const is_posix = switch (@import("builtin").os.tag) { // From std.time.zig L125
-            .windows, .uefi, .wasi => false,
-            else => true,
+    pub fn init() Performance {
+        return .{
+            .time_origin = milliTimestamp(),
         };
-        const zero = std.time.Instant{ .timestamp = if (!is_posix) 0 else .{ .sec = 0, .nsec = 0 } };
-        const started = self.time_origin.started.since(zero);
-        return limitedResolutionMs(started);
     }
 
-    pub fn _now(self: *Performance) f64 {
-        return limitedResolutionMs(self.time_origin.read());
+    pub fn get_timeOrigin(self: *const Performance) u64 {
+        return self.time_origin;
+    }
+
+    pub fn reset(self: *Performance) void {
+        self.time_origin = milliTimestamp();
+    }
+
+    pub fn _now(self: *const Performance) u64 {
+        return milliTimestamp() - self.time_origin;
     }
 
     pub fn _mark(_: *Performance, name: []const u8, _options: ?PerformanceMark.Options, page: *Page) !PerformanceMark {
@@ -152,14 +152,14 @@ pub const PerformanceMark = struct {
 
     const Options = struct {
         detail: ?Env.JsObject = null,
-        start_time: ?f64 = null,
+        startTime: ?f64 = null,
     };
 
     pub fn constructor(name: []const u8, _options: ?Options, page: *Page) !PerformanceMark {
         const perf = &page.window.performance;
 
         const options = _options orelse Options{};
-        const start_time = options.start_time orelse perf._now();
+        const start_time = options.startTime orelse @as(f64, @floatFromInt(perf._now()));
 
         if (start_time < 0.0) {
             return error.TypeError;
@@ -181,16 +181,13 @@ pub const PerformanceMark = struct {
 const testing = @import("./../../testing.zig");
 
 test "Performance: get_timeOrigin" {
-    var perf = Performance{ .time_origin = try std.time.Timer.start() };
+    var perf = Performance.init();
     const time_origin = perf.get_timeOrigin();
     try testing.expect(time_origin >= 0);
-
-    // Check resolution
-    try testing.expectDelta(@rem(time_origin * std.time.us_per_ms, 100.0), 0.0, 0.2);
 }
 
 test "Performance: now" {
-    var perf = Performance{ .time_origin = try std.time.Timer.start() };
+    var perf = Performance.init();
 
     // Monotonically increasing
     var now = perf._now();
@@ -198,16 +195,12 @@ test "Performance: now" {
         try testing.expectEqual(now, 0);
         now = perf._now();
     }
-    // Check resolution
-    try testing.expectDelta(@rem(now * std.time.us_per_ms, 100.0), 0.0, 0.1);
 
     var after = perf._now();
     while (after <= now) { // Loop untill after > now
         try testing.expectEqual(after, now);
         after = perf._now();
     }
-    // Check resolution
-    try testing.expectDelta(@rem(after * std.time.us_per_ms, 100.0), 0.0, 0.1);
 }
 
 test "Browser.Performance.Mark" {
@@ -215,13 +208,17 @@ test "Browser.Performance.Mark" {
     defer runner.deinit();
 
     try runner.testCases(&.{
-        .{ "let performance = window.performance", "undefined" },
+        .{ "let performance = window.performance", null },
         .{ "performance instanceof Performance", "true" },
-        .{ "let mark = performance.mark(\"start\")", "undefined" },
-        .{ "mark instanceof PerformanceMark", "true" },
-        .{ "mark.name", "start" },
-        .{ "mark.entryType", "mark" },
-        .{ "mark.duration", "0" },
-        .{ "mark.detail", "null" },
+
+        .{ "let mark1 = performance.mark(\"start\")", null },
+        .{ "mark1 instanceof PerformanceMark", "true" },
+        .{ "mark1.name", "start" },
+        .{ "mark1.entryType", "mark" },
+        .{ "mark1.duration", "0" },
+        .{ "mark1.detail", "null" },
+
+        .{ "let mark2 = performance.mark(\"start\", {startTime: 32939393.9})", null },
+        .{ "mark2.startTime", "32939393.9" },
     }, .{});
 }

src/browser/html/window.zig

@@ -76,7 +76,7 @@ pub const Window = struct {
             .document = html_doc,
             .target = target orelse "",
             .navigator = navigator orelse .{},
-            .performance = .{ .time_origin = try std.time.Timer.start() },
+            .performance = Performance.init(),
         };
     }
 
@@ -86,7 +86,7 @@ pub const Window = struct {
     }
 
     pub fn replaceDocument(self: *Window, doc: *parser.DocumentHTML) !void {
-        self.performance.time_origin.reset(); // When to reset see: https://developer.mozilla.org/en-US/docs/Web/API/Performance/timeOrigin
+        self.performance.reset(); // When to reset see: https://developer.mozilla.org/en-US/docs/Web/API/Performance/timeOrigin
         self.document = doc;
         try parser.documentHTMLSetLocation(Location, doc, &self.location);
     }

src/browser/page.zig

@@ -1101,8 +1101,7 @@ pub const NavigateOpts = struct {
 };
 
 fn timestamp() u32 {
-    const ts = std.posix.clock_gettime(std.posix.CLOCK.MONOTONIC) catch unreachable;
-    return @intCast(ts.sec);
+    return @import("../datetime.zig").timestamp();
 }
 
 // A callback from libdom whenever a script tag is added to the DOM.

src/datetime.zig

@@ -502,6 +502,28 @@ pub const DateTime = struct {
     }
 };
 
+pub fn timestamp() u32 {
+    const ts = timespec();
+    return @intCast(ts.sec);
+}
+
+pub fn milliTimestamp() u64 {
+    const ts = timespec();
+    return @as(u64, @intCast(ts.sec)) * 1000 + @as(u64, @intCast(@divTrunc(ts.nsec, 1_000_000)));
+}
+
+fn timespec() std.posix.timespec {
+    const clock_id = switch (@import("builtin").os.tag) {
+        .freebsd, .dragonfly => std.posix.CLOCK.MONOTONIC_FAST,
+        .macos, .ios, .tvos, .watchos, .visionos => std.posix.CLOCK.UPTIME_RAW, // continues counting while suspended
+        .linux => std.posix.CLOCK.BOOTTIME, // continues counting while suspended
+        else => std.posix.CLOCK.MONOTONIC,
+    };
+    // we don't currently support platforms where, at the very least,
+    // posix.CLOCK.MONOTONIC wouldn't be available.
+    return std.posix.clock_gettime(clock_id) catch unreachable;
+}
+
 fn writeDate(into: []u8, date: Date) u8 {
     var buf: []u8 = undefined;
     // cast year to a u16 so it doesn't insert a sign

src/log.zig

@@ -321,14 +321,14 @@ fn writeString(comptime format: Format, value: []const u8, writer: anytype) !voi
     return writer.writeByte('"');
 }
 
-fn timestamp() i64 {
+fn timestamp() u64 {
     if (comptime @import("builtin").is_test) {
         return 1739795092929;
     }
-    return std.time.milliTimestamp();
+    return @import("datetime.zig").milliTimestamp();
 }
 
-var first_log: i64 = 0;
+var first_log: u64 = 0;
 fn elapsed() struct { time: f64, unit: []const u8 } {
     const now = timestamp();
 

src/server.zig

@@ -897,8 +897,7 @@ fn buildJSONVersionResponse(
 }
 
 fn timestamp() u32 {
-    const ts = std.posix.clock_gettime(std.posix.CLOCK.MONOTONIC) catch unreachable;
-    return @intCast(ts.sec);
+    return @import("datetime.zig").timestamp();
 }
 
 // In-place string lowercase