Copy the commonKotlin Instant implementation to kotlinx.time

Author: dkhalanskyjb

fake-kotlinx-time/build.gradle.kts

@@ -13,6 +13,7 @@ java {
 }
 
 kotlin {
+    explicitApi()
     infra {
         target("linuxX64")
         target("linuxArm64")

fake-kotlinx-time/common/src/Instant.kt

@@ -0,0 +1,10 @@
+/*
+ * Copyright 2019-2024 JetBrains s.r.o. and contributors.
+ * Use of this source code is governed by the Apache 2.0 License that can be found in the LICENSE.txt file.
+ */
+
+package kotlinx.time
+
+import kotlin.js.Date
+
+internal actual fun currentTime(): Instant = Instant.fromEpochMilliseconds(Date().getTime().toLong())

fake-kotlinx-time/js/src/Platform.kt

@@ -0,0 +1,8 @@
+/*
+ * Copyright 2019-2024 JetBrains s.r.o. and contributors.
+ * Use of this source code is governed by the Apache 2.0 License that can be found in the LICENSE.txt file.
+ */
+
+package kotlinx.time
+
+internal actual fun currentTime(): Instant = java.time.Instant.now().toKotlinInstant()

fake-kotlinx-time/jvm/src/Platform.kt

@@ -0,0 +1,21 @@
+/*
+ * Copyright 2019-2024 JetBrains s.r.o. and contributors.
+ * Use of this source code is governed by the Apache 2.0 License that can be found in the LICENSE.txt file.
+ */
+
+package kotlinx.time
+import kotlinx.cinterop.*
+import platform.posix.*
+
+@OptIn(ExperimentalForeignApi::class, UnsafeNumber::class)
+internal actual fun currentTime(): Instant = memScoped {
+    val tm = alloc<timespec>()
+    val error = clock_gettime(CLOCK_REALTIME.convert(), tm.ptr)
+    check(error == 0) { "Error when reading the system clock: ${strerror(errno)?.toKString() ?: "Unknown error"}" }
+    try {
+        require(tm.tv_nsec in 0 until NANOS_PER_ONE)
+        Instant(tm.tv_sec.convert(), tm.tv_nsec.convert())
+    } catch (e: IllegalArgumentException) {
+        throw IllegalStateException("The readings from the system clock (${tm.tv_sec} seconds, ${tm.tv_nsec} nanoseconds) are not representable as an Instant")
+    }
+}

fake-kotlinx-time/native/src/Platform.kt

@@ -0,0 +1,12 @@
+/*
+ * Copyright 2019-2024 JetBrains s.r.o. and contributors.
+ * Use of this source code is governed by the Apache 2.0 License that can be found in the LICENSE.txt file.
+ */
+
+package kotlinx.time
+
+internal actual fun currentTime(): Instant = Instant.fromEpochMilliseconds(Date().getTime().toLong())
+
+private external class Date {
+    fun getTime(): Double
+}

fake-kotlinx-time/wasmJs/src/Platform.kt

@@ -0,0 +1,38 @@
+/*
+ * Copyright 2019-2024 JetBrains s.r.o. and contributors.
+ * Use of this source code is governed by the Apache 2.0 License that can be found in the LICENSE.txt file.
+ */
+
+package kotlinx.time
+
+import kotlin.wasm.WasmImport
+import kotlin.wasm.unsafe.UnsafeWasmMemoryApi
+import kotlin.wasm.unsafe.withScopedMemoryAllocator
+
+/**
+ * Return the time value of a clock. Note: This is similar to `clock_gettime` in POSIX.
+ */
+@WasmImport("wasi_snapshot_preview1", "clock_time_get")
+private external fun wasiRawClockTimeGet(clockId: Int, precision: Long, resultPtr: Int): Int
+
+private const val CLOCKID_REALTIME = 0
+
+@OptIn(UnsafeWasmMemoryApi::class)
+private fun clockTimeGet(): Long = withScopedMemoryAllocator { allocator ->
+    val rp0 = allocator.allocate(8)
+    val ret = wasiRawClockTimeGet(
+        clockId = CLOCKID_REALTIME,
+        precision = 1,
+        resultPtr = rp0.address.toInt()
+    )
+    if (ret == 0) {
+        rp0.loadLong()
+    } else {
+        error("WASI call failed with $ret")
+    }
+}
+
+internal actual fun currentTime(): Instant = clockTimeGet().let { time ->
+    // Instant.MAX and Instant.MIN are never going to be exceeded using just the Long number of nanoseconds
+    Instant(time.floorDiv(NANOS_PER_ONE.toLong()), time.mod(NANOS_PER_ONE.toLong()).toInt())
+}