feat: add time syscall & command in shell

kernel/src/Timekeeping/Time.cpp

@@ -4,12 +4,70 @@
 */
 
 #include "Time.hpp"
+#include "ApicTimer.hpp"
 #include <Terminal/Terminal.hpp>
 #include <CppLib/Stream.hpp>
 
 using namespace Kt;
 
+static int64_t g_bootEpoch = 0;
+
+static bool IsLeapYear(int year) {
+    return (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0);
+}
+
+static int DaysInMonth(int month, int year) {
+    static const int days[] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
+    if (month == 2 && IsLeapYear(year)) return 29;
+    return days[month];
+}
+
+static int64_t DateToEpoch(int year, int month, int day, int hour, int minute, int second) {
+    int64_t days = 0;
+    for (int y = 1970; y < year; y++) {
+        days += IsLeapYear(y) ? 366 : 365;
+    }
+    for (int m = 1; m < month; m++) {
+        days += DaysInMonth(m, year);
+    }
+    days += day - 1;
+    return days * 86400 + hour * 3600 + minute * 60 + second;
+}
+
+static Timekeeping::DateTime EpochToDate(int64_t epoch) {
+    Timekeeping::DateTime dt = {};
+    int64_t rem = epoch;
+    int year = 1970;
+    while (true) {
+        int64_t daysInYear = IsLeapYear(year) ? 366 : 365;
+        if (rem < daysInYear * 86400) break;
+        rem -= daysInYear * 86400;
+        year++;
+    }
+    dt.Year = (uint16_t)year;
+
+    int dayOfYear = (int)(rem / 86400);
+    rem -= (int64_t)dayOfYear * 86400;
+
+    int month = 1;
+    while (month <= 12) {
+        int dim = DaysInMonth(month, year);
+        if (dayOfYear < dim) break;
+        dayOfYear -= dim;
+        month++;
+    }
+    dt.Month = (uint8_t)month;
+    dt.Day = (uint8_t)(dayOfYear + 1);
+
+    dt.Hour = (uint8_t)(rem / 3600);
+    rem %= 3600;
+    dt.Minute = (uint8_t)(rem / 60);
+    dt.Second = (uint8_t)(rem % 60);
+    return dt;
+}
+
 void Timekeeping::Init(uint16_t Year, uint8_t Month, uint8_t Day, uint8_t Hour, uint8_t Minute, uint8_t Second) {
+    g_bootEpoch = DateToEpoch(Year, Month, Day, Hour, Minute, Second);
     /* Hardcode CET for now */
     TimeZone CET = {
         "Central European Time",
@@ -63,4 +121,12 @@ void Timekeeping::Init(uint16_t Year, uint8_t Month, uint8_t Day, uint8_t Hour,
     CString dateString = panelStr.c_str();
 
     UpdatePanelBar(dateString);
+}
+
+int64_t Timekeeping::GetUnixTimestamp() {
+    return g_bootEpoch + (int64_t)(Timekeeping::GetMilliseconds() / 1000);
+}
+
+Timekeeping::DateTime Timekeeping::GetDateTime() {
+    return EpochToDate(GetUnixTimestamp());
 }

kernel/src/Timekeeping/Time.hpp

@@ -41,5 +41,16 @@ namespace Timekeeping {
         "December"
     };
 
+    struct DateTime {
+        uint16_t Year;
+        uint8_t Month;
+        uint8_t Day;
+        uint8_t Hour;
+        uint8_t Minute;
+        uint8_t Second;
+    };
+
     void Init(uint16_t Year, uint8_t Month, uint8_t Day, uint8_t Hour, uint8_t Minute, uint8_t Second);
+    int64_t GetUnixTimestamp();
+    DateTime GetDateTime();
 };