增加了timekeeping模块 (#106)

* 增加了timekeeping模块

* 格式化文档和细节更改

Co-authored-by: longjin <longjin@RinGoTek.cn>

kernel/src/time/mod.rs

@@ -0,0 +1 @@
+pub mod timekeep;

kernel/src/time/timekeep.rs

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+#![allow(dead_code)]
+use crate::include::bindings::bindings::{rtc_get_cmos_time, rtc_time_t};
+
+#[allow(non_camel_case_types)]
+pub type ktime_t = i64;
+
+// @brief 将ktime_t类型转换为纳秒类型
+#[inline]
+fn ktime_to_ns(kt: ktime_t) -> i64 {
+    return kt as i64;
+}
+
+/// @brief 从RTC获取当前时间，然后计算时间戳。
+/// 时间戳为从UTC+0 1970-01-01 00:00到当前UTC+0时间，所经过的纳秒数。
+/// 注意，由于当前未引入时区，因此本函数默认时区为UTC+8来计算
+fn ktime_get_real() -> ktime_t {
+    let mut rtc_time: rtc_time_t = rtc_time_t {
+        second: (0),
+        minute: (0),
+        hour: (0),
+        day: (0),
+        month: (0),
+        year: (0),
+    };
+
+    unsafe {
+        //调用rtc.h里面的函数
+        rtc_get_cmos_time(&mut rtc_time);
+    }
+
+    let mut day_count: i32 = 0;
+    for year in 1970..rtc_time.year {
+        let leap: bool = (year % 4 == 0) && (year % 100 != 0) || (year % 400 == 0);
+        if leap {
+            day_count += 366;
+        } else {
+            day_count += 365;
+        }
+        //println!("{},{}",year,day_count);
+    }
+    //println!("day count1: {}",day_count);
+    for month in 1..rtc_time.month {
+        match month {
+            1 | 3 | 5 | 7 | 8 | 10 | 12 => day_count += 31,
+            2 => day_count += 28,
+            4 | 6 | 9 | 11 => day_count += 30,
+            _ => day_count += 0,
+        }
+        //println!("{}:{}",month,day_count);
+    }
+
+    day_count += rtc_time.day - 1;
+    //println!("day count2: {}",day_count);
+    //转换成纳秒
+    let timestamp: ktime_t = day_count as i64 * 86_400_000_000_000i64
+        + (rtc_time.hour - 8) as i64 * 3_600_000_000_000i64
+        + rtc_time.minute as i64 * 60_000_000_000i64
+        + rtc_time.second as i64 * 1_000_000_000i64 as ktime_t;
+
+    return timestamp;
+}
+
+/// @brief 暴露给外部使用的接口，返回一个时间戳
+#[inline]
+pub fn ktime_get_real_ns() -> i64 {
+    let kt: ktime_t = ktime_get_real();
+    return ktime_to_ns(kt);
+}