LibJS: Implement Temporal.now.instant()

Author: https://github.com/linusg
Commit: https://github.com/SerenityOS/serenity/commit/3a39ff8f40d
Pull-request: https://github.com/SerenityOS/serenity/pull/8534

Userland/Libraries/LibJS/Runtime/CommonPropertyNames.h

@@ -190,6 +190,7 @@ namespace JS {
     P(indexOf)                               \
     P(info)                                  \
     P(input)                                 \
+    P(instant)                               \
     P(is)                                    \
     P(isArray)                               \
     P(isExtensible)                          \

Userland/Libraries/LibJS/Runtime/Temporal/Now.cpp

@@ -4,9 +4,12 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <LibCrypto/BigInt/SignedBigInteger.h>
 #include <LibJS/Runtime/GlobalObject.h>
+#include <LibJS/Runtime/Temporal/Instant.h>
 #include <LibJS/Runtime/Temporal/Now.h>
 #include <LibJS/Runtime/Temporal/TimeZone.h>
+#include <time.h>
 
 namespace JS::Temporal {
 
@@ -24,6 +27,7 @@ void Now::initialize(GlobalObject& global_object)
     u8 attr = Attribute::Writable | Attribute::Configurable;
 
     define_native_function(vm.names.timeZone, time_zone, 0, attr);
+    define_native_function(vm.names.instant, instant, 0, attr);
 }
 
 // 2.1.1 Temporal.now.timeZone ( ), https://tc39.es/proposal-temporal/#sec-temporal.now.timezone
@@ -33,6 +37,13 @@ JS_DEFINE_NATIVE_FUNCTION(Now::time_zone)
     return system_time_zone(global_object);
 }
 
+// 2.1.2 Temporal.now.instant ( ), https://tc39.es/proposal-temporal/#sec-temporal.now.instant
+JS_DEFINE_NATIVE_FUNCTION(Now::instant)
+{
+    // 1. Return ? SystemInstant().
+    return system_instant(global_object);
+}
+
 // 2.2.1 SystemTimeZone ( ), https://tc39.es/proposal-temporal/#sec-temporal-systemtimezone
 Object* system_time_zone(GlobalObject& global_object)
 {
@@ -43,4 +54,37 @@ Object* system_time_zone(GlobalObject& global_object)
     return create_temporal_time_zone(global_object, identifier);
 }
 
+// 2.2.2 SystemUTCEpochNanoseconds ( )
+BigInt* system_utc_epoch_nanoseconds(GlobalObject& global_object)
+{
+    // 1. Let ns be the approximate current UTC date and time, in nanoseconds since the epoch.
+    struct timespec now;
+    clock_gettime(CLOCK_REALTIME, &now);
+    Checked<i64> ns_timestamp;
+    ns_timestamp += now.tv_sec;
+    ns_timestamp *= 1000000000;
+    ns_timestamp += now.tv_nsec;
+    if (ns_timestamp.has_overflow()) {
+        // TODO: Deal with this before 2262-04-21T00:47:16Z.
+        VERIFY_NOT_REACHED();
+    }
+    auto ns = Crypto::SignedBigInteger::create_from(ns_timestamp.value());
+
+    // 2. Set ns to the result of clamping ns between −8.64 × 10^21 and 8.64 × 10^21.
+    // Uhh, these don't even fit in an i64... ¯\_(ツ)_/¯
+
+    // 3. Return ℤ(ns).
+    return js_bigint(global_object.heap(), move(ns));
+}
+
+// 2.2.3 SystemInstant ( )
+Object* system_instant(GlobalObject& global_object)
+{
+    // 1. Let ns be ! SystemUTCEpochNanoseconds().
+    auto* ns = system_utc_epoch_nanoseconds(global_object);
+
+    // 2. Return ? CreateTemporalInstant(ns).
+    return create_temporal_instant(global_object, *ns);
+}
+
 }

Userland/Libraries/LibJS/Runtime/Temporal/Now.h

@@ -20,8 +20,11 @@ public:
 
 private:
     JS_DECLARE_NATIVE_FUNCTION(time_zone);
+    JS_DECLARE_NATIVE_FUNCTION(instant);
 };
 
 Object* system_time_zone(GlobalObject&);
+BigInt* system_utc_epoch_nanoseconds(GlobalObject&);
+Object* system_instant(GlobalObject&);
 
 }