1 files changed, 122 insertions, 0 deletions
diff --git a/rust/src/helpers.rs b/rust/src/helpers.rs
new file mode 100644
index 0000000..364075a
--- /dev/null
+++ b/rust/src/helpers.rs
@@ -0,0 +1,122 @@
+use crate::constants::{
+    DAYS_PER_L_YEAR, DAYS_PER_N_YEAR, DAY_OF_WEEK_TABLE, EPOCH_YEAR, MONTHS_OFFSETS,
+    SECS_PER_100_YEARS, SECS_PER_400_YEARS, SECS_PER_4_YEARS, SECS_PER_DAY, SECS_PER_HOUR,
+    SECS_PER_MIN, SECS_PER_YEAR, TM_DECEMBER, TM_JANUARY,
+};
+
+fn p(year: i32) -> i32 {
+    year + year / 4 - year / 100 + year / 400
+}
+
+pub fn is_leap(year: i32) -> bool {
+    year % 4 == 0 && (year % 100 != 0 || year % 400 == 0)
+}
+
+pub fn is_long_year(year: i32) -> bool {
+    (p(year) % 7 == 4) || (p(year - 1) % 7 == 3)
+}
+
+pub fn days_in_year(year: i32) -> u32 {
+    if is_leap(year) {
+        return DAYS_PER_L_YEAR;
+    }
+
+    DAYS_PER_N_YEAR
+}
+
+pub fn week_day(year: i32, month: u32, day: u32) -> u32 {
+    let y: i32 = year - i32::from(month < 3);
+
+    let w: i32 = (p(y) + DAY_OF_WEEK_TABLE[(month - 1) as usize] as i32 + day as i32) % 7;
+
+    if w == 0 {
+        return 7;
+    }
+
+    w.unsigned_abs()
+}
+
+pub fn day_number(year: i32, month: u8, day: u8) -> i32 {
+    let m = i32::from((month + 9) % 12);
+    let y = year - m / 10;
+
+    365 * y + y / 4 - y / 100 + y / 400 + (m * 306 + 5) / 10 + (i32::from(day) - 1)
+}
+
+pub fn local_time(
+    unix_time: f64,
+    utc_offset: isize,
+    microsecond: usize,
+) -> (usize, usize, usize, usize, usize, usize, usize) {
+    let mut year: usize = EPOCH_YEAR as usize;
+    let mut seconds: isize = unix_time.floor() as isize;
+
+    // Shift to a base year that is 400-year aligned.
+    if seconds >= 0 {
+        seconds -= (10957 * SECS_PER_DAY as usize) as isize;
+        year += 30; // == 2000
+    } else {
+        seconds += ((146_097 - 10957) * SECS_PER_DAY as usize) as isize;
+        year -= 370; // == 1600
+    }
+
+    seconds += utc_offset;
+
+    // Handle years in chunks of 400/100/4/1
+    year += 400 * (seconds / SECS_PER_400_YEARS as isize) as usize;
+    seconds %= SECS_PER_400_YEARS as isize;
+    if seconds < 0 {
+        seconds += SECS_PER_400_YEARS as isize;
+        year -= 400;
+    }
+
+    let mut leap_year = 1; // 4-century aligned
+    let mut sec_per_100years = SECS_PER_100_YEARS[leap_year] as isize;
+
+    while seconds >= sec_per_100years {
+        seconds -= sec_per_100years;
+        year += 100;
+        leap_year = 0; // 1-century, non 4-century aligned
+        sec_per_100years = SECS_PER_100_YEARS[leap_year] as isize;
+    }
+
+    let mut sec_per_4years = SECS_PER_4_YEARS[leap_year] as isize;
+    while seconds >= sec_per_4years {
+        seconds -= sec_per_4years;
+        year += 4;
+        leap_year = 1; // 4-year, non century aligned
+        sec_per_4years = SECS_PER_4_YEARS[leap_year] as isize;
+    }
+
+    let mut sec_per_year = SECS_PER_YEAR[leap_year] as isize;
+    while seconds >= sec_per_year {
+        seconds -= sec_per_year;
+        year += 1;
+        leap_year = 0; // non 4-year aligned
+        sec_per_year = SECS_PER_YEAR[leap_year] as isize;
+    }
+
+    // Handle months and days
+    let mut month = TM_DECEMBER + 1;
+    let mut day: usize = (seconds / (SECS_PER_DAY as isize) + 1) as usize;
+    seconds %= SECS_PER_DAY as isize;
+
+    let mut month_offset: usize;
+    while month != (TM_JANUARY + 1) {
+        month_offset = MONTHS_OFFSETS[leap_year][month] as usize;
+        if day > month_offset {
+            day -= month_offset;
+            break;
+        }
+
+        month -= 1;
+    }
+
+    // Handle hours, minutes and seconds
+    let hour: usize = (seconds / SECS_PER_HOUR as isize) as usize;
+    seconds %= SECS_PER_HOUR as isize;
+    let minute: usize = (seconds / SECS_PER_MIN as isize) as usize;
+    let second: usize = (seconds % SECS_PER_MIN as isize) as usize;
+
+    (year, month, day, hour, minute, second, microsecond)
+}