Create the module to convert datetime to unix epoch

src/datetime.rs

@@ -0,0 +1,122 @@
+// This code was extracted from http://git.musl-libc.org/cgit/musl/tree/src/time?h=v0.9.15
+
+pub struct Datetime {
+    pub year: u16,
+    pub month: u8,
+    pub day: u8,
+    pub hours: u8,
+    pub minutes: u8,
+    pub seconds: u8,
+}
+
+impl Datetime {
+    pub fn unix_epoch(&self) -> u64 {
+        let mut year: i64 = self.year as i64 - 1900;
+        let mut month: i64 = self.month as i64 - 1;
+        if month >= 12 || month < 0 {
+            let mut adj = month / 12;
+            month %= 12;
+            if month < 0 {
+                adj -= 1;
+                month += 12;
+            }
+            year += adj as i64;
+        }
+        let (mut t, is_leap) = year_to_secs(year);
+        t += month_to_secs(month, is_leap);
+        t += 86400 * (self.day as i64 - 1);
+        t += 3600 * self.hours as i64;
+        t += 60 * self.minutes as i64;
+        t += self.seconds as i64;
+        t as u64
+    }
+}
+
+fn year_to_secs(year: i64) -> (i64, bool) {
+    let is_leap: bool;
+    let res: i64;
+
+    if year - 2 <= 136 {
+        let y = year as i32;
+        let mut leaps = (y - 68) >> 2;
+        if !((y - 68) & 3 != 0) {
+            leaps -= 1;
+            is_leap = true;
+        } else {
+            is_leap = false;
+        }
+        res = 31536000 * (y - 70) as i64 + 86400 * leaps as i64;
+    } else {
+        let mut cycles: i64;
+        let centuries: i64;
+        let mut leaps: i64;
+        let mut rem: i64;
+
+        cycles = (year - 100) / 400;
+        rem = (year - 100) % 400;
+        if rem < 0 {
+            cycles -= 1;
+            rem += 400;
+        }
+        if rem == 0 {
+            is_leap = true;
+            centuries = 0;
+            leaps = 0;
+        } else {
+            if rem >= 200 {
+                if rem >= 300 {
+                    centuries = 3;
+                    rem -= 300;
+                } else {
+                    centuries = 2;
+                    rem -= 200;
+                }
+            } else {
+                if rem >= 100 {
+                    centuries = 1;
+                    rem -= 100;
+                } else {
+                    centuries = 0;
+                }
+            }
+            if rem == 0 {
+                is_leap = false;
+                leaps = 0;
+            } else {
+                leaps = rem / 4;
+                rem %= 4;
+                is_leap = rem == 0;
+            }
+        }
+
+        leaps += 97 * cycles + 24 * centuries - (is_leap as i64);
+
+        res = (year - 100) * 31536000 + leaps * 86400 + 946684800 + 86400;
+    }
+
+    (res, is_leap)
+}
+
+fn month_to_secs(month: i64, is_leap: bool) -> i64 {
+    const SECS_THROUGH_MONTH: [i64; 12] = [
+        0,           // Jan
+        31 * 86400,  // Feb
+        59 * 86400,  // Mar
+        90 * 86400,  // Apr
+        120 * 86400, // May
+        151 * 86400, // Jun
+        181 * 86400, // Jul
+        212 * 86400, // Aug
+        243 * 86400, // Sep
+        273 * 86400, // Oct
+        304 * 86400, // Nov
+        334 * 86400, // Dec
+    ];
+
+    let mut t = SECS_THROUGH_MONTH[month as usize];
+    if is_leap && month >= 2 {
+        t += 86400;
+    }
+
+    t
+}