feat: enhance timer

kernel/include/apic/timer.h

@@ -1,15 +1,57 @@
 #pragma once
 
 #include "acpi/madt.h"
-#include "util/optional.h"
 
 namespace apic {
 
-struct lapic_timer_calibration_t {
-    uint64_t tsc_frequency_hz;
+struct duration_t {
+    uint64_t timer_count;
 };
 
-optional<lapic_timer_calibration_t> calibrateTimer(const acpi::Madt& madt);
+struct timestamp_t {
+    uint64_t timer_count;
+};
+
+constexpr duration_t operator+(duration_t left, duration_t right) {
+    return duration_t{left.timer_count + right.timer_count};
+}
+
+constexpr duration_t operator-(duration_t left, duration_t right) {
+    return duration_t{left.timer_count - right.timer_count};
+}
+
+constexpr duration_t operator*(duration_t duration, uint64_t scalar) {
+    return duration_t{duration.timer_count * scalar};
+}
+
+constexpr duration_t operator*(uint64_t scalar, duration_t duration) {
+    return duration_t{duration.timer_count * scalar};
+}
+
+constexpr timestamp_t operator+(timestamp_t timestamp, duration_t duration) {
+    return timestamp_t{timestamp.timer_count + duration.timer_count};
+}
+
+constexpr timestamp_t operator+(duration_t duration, timestamp_t timestamp) {
+    return timestamp_t{timestamp.timer_count + duration.timer_count};
+}
+
+constexpr timestamp_t operator-(timestamp_t timestamp, duration_t duration) {
+    return timestamp_t{timestamp.timer_count - duration.timer_count};
+}
+
+constexpr duration_t operator-(timestamp_t left, timestamp_t right) {
+    return duration_t{left.timer_count - right.timer_count};
+}
+
+bool calibrateTimer(const acpi::Madt& madt);
+
+duration_t seconds(uint64_t count);
+duration_t milliseconds(uint64_t count);
+duration_t microseconds(uint64_t count);
+duration_t nanoseconds(uint64_t count);
+
+timestamp_t now();
 
 // TODO: when dynamic allocation and lists are available
 // struct Timer {};

kernel/include/util/function.h

@@ -23,3 +23,10 @@ auto construct() {
         return Type{forward<decltype(args)>(args)...};
     };
 }
+
+template<typename V>
+auto constant(V v) {
+    return [v](auto _) {
+        return v;
+    };
+}

kernel/include/util/optional.h

@@ -183,3 +183,24 @@ public:
         }
     }
 };
+
+template<typename T>
+struct as_optional {
+    using type = optional<T>;
+};
+template<typename T>
+struct as_optional<optional<T>> {
+    using type = optional<T>;
+};
+template<typename T>
+using as_optional_t = typename as_optional<T>::type;
+
+template<typename Func>
+auto lift(Func func) {
+    return [func](const auto&... optionals) -> as_optional_t<decltype(func(optionals.value()...))> {
+        if ((optionals.has_value() && ...)) {
+            return func(optionals.value()...);
+        }
+        return nullopt;
+    };
+}