Move days_in_month to time-core

Author: jhpratt

time-core/src/hint.rs

@@ -0,0 +1,26 @@
+//! Hints to the compiler that affects how code should be emitted or optimized.
+
+#![allow(dead_code)] // may be used in the future and has minimal overhead
+
+/// Indicate that a given branch is **not** likely to be taken, relatively speaking.
+#[inline(always)]
+#[cold]
+pub(crate) const fn cold_path() {}
+
+/// Indicate that a given condition is likely to be true.
+#[inline(always)]
+pub(crate) const fn likely(b: bool) -> bool {
+    if !b {
+        cold_path();
+    }
+    b
+}
+
+/// Indicate that a given condition is likely to be false.
+#[inline(always)]
+pub(crate) const fn unlikely(b: bool) -> bool {
+    if b {
+        cold_path();
+    }
+    b
+}

time-core/src/lib.rs

@@ -8,4 +8,5 @@
 #![doc(test(attr(deny(warnings))))]
 
 pub mod convert;
+mod hint;
 pub mod util;

time-core/src/util.rs

@@ -1,5 +1,7 @@
 //! Utility functions.
 
+use crate::hint;
+
 /// Returns if the provided year is a leap year in the proleptic Gregorian calendar. Uses
 /// [astronomical year numbering](https://en.wikipedia.org/wiki/Astronomical_year_numbering).
 ///
@@ -61,3 +63,26 @@ pub const fn weeks_in_year(year: i32) -> u8 {
         _ => 52,
     }
 }
+
+/// Get the number of days in the month of a given year.
+///
+/// ```rust
+/// # use time_core::util::days_in_month;
+/// assert_eq!(days_in_month(2, 2020), 29);
+/// ```
+///
+/// Note: This function is not exposed by the `time` crate. It is an implementation detail.
+pub const fn days_in_month(month: u8, year: i32) -> u8 {
+    debug_assert!(month >= 1);
+    debug_assert!(month <= 12);
+
+    if hint::unlikely(month == 2) {
+        if is_leap_year(year) {
+            29
+        } else {
+            28
+        }
+    } else {
+        30 | month ^ (month >> 3)
+    }
+}

time/src/month.rs

@@ -7,7 +7,7 @@ use core::str::FromStr;
 use powerfmt::smart_display::{FormatterOptions, Metadata, SmartDisplay};
 
 use self::Month::*;
-use crate::{error, hint, util};
+use crate::{error, util};
 
 /// Months of the year.
 #[repr(u8)]
@@ -72,16 +72,7 @@ impl Month {
     /// assert_eq!(Month::February.length(2020), 29);
     /// ```
     pub const fn length(self, year: i32) -> u8 {
-        let val = self as u8;
-        if hint::unlikely(val == 2) {
-            if util::is_leap_year(year) {
-                29
-            } else {
-                28
-            }
-        } else {
-            30 | val ^ (val >> 3)
-        }
+        util::days_in_month(self, year)
     }
 
     /// Get the previous month.

time/src/util.rs

@@ -21,7 +21,7 @@ pub(crate) enum DateAdjustment {
 /// assert_eq!(util::days_in_month(Month::February, 2020), 29);
 /// ```
 pub const fn days_in_month(month: Month, year: i32) -> u8 {
-    month.length(year)
+    time_core::util::days_in_month(month as u8, year)
 }
 
 /// Get the number of days in the month of a given year.
@@ -36,7 +36,7 @@ pub const fn days_in_month(month: Month, year: i32) -> u8 {
     note = "use `days_in_month` or `Month::length` instead"
 )]
 pub const fn days_in_year_month(year: i32, month: Month) -> u8 {
-    month.length(year)
+    days_in_month(month, year)
 }
 
 /// Update time zone information from the system.