Make char methods const

[rust.git] / library / core / src / num / mod.rs

diff --git a/library/core/src/num/mod.rs b/library/core/src/num/mod.rs
index 6bdfa18fa434ccf8ccf53a9f1499b22bf40c986c..8b81d41b8c067ffc49fd95b1136a0e783ed0b07e 100644 (file)
--- a/library/core/src/num/mod.rs
+++ b/library/core/src/num/mod.rs
@@ -152,6 +152,9 @@ impl isize {
      usize_isize_to_xe_bytes_doc!(), usize_isize_from_xe_bytes_doc!() }
 }
 
+/// If 6th bit set ascii is upper case.
+const ASCII_CASE_MASK: u8 = 0b0010_0000;
+
 #[lang = "u8"]
 impl u8 {
     uint_impl! { u8, u8, 8, 255, 2, "0x82", "0xa", "0x12", "0x12", "0x48", "[0x12]",
@@ -192,10 +195,11 @@ pub const fn is_ascii(&self) -> bool {
     ///
     /// [`make_ascii_uppercase`]: #method.make_ascii_uppercase
     #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
+    #[rustc_const_stable(feature = "const_ascii_methods_on_intrinsics", since = "1.50.0")]
     #[inline]
-    pub fn to_ascii_uppercase(&self) -> u8 {
+    pub const fn to_ascii_uppercase(&self) -> u8 {
         // Unset the fifth bit if this is a lowercase letter
-        *self & !((self.is_ascii_lowercase() as u8) << 5)
+        *self & !((self.is_ascii_lowercase() as u8) * ASCII_CASE_MASK)
     }
 
     /// Makes a copy of the value in its ASCII lower case equivalent.
@@ -215,10 +219,17 @@ pub fn to_ascii_uppercase(&self) -> u8 {
     ///
     /// [`make_ascii_lowercase`]: #method.make_ascii_lowercase
     #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
+    #[rustc_const_stable(feature = "const_ascii_methods_on_intrinsics", since = "1.50.0")]
     #[inline]
-    pub fn to_ascii_lowercase(&self) -> u8 {
+    pub const fn to_ascii_lowercase(&self) -> u8 {
         // Set the fifth bit if this is an uppercase letter
-        *self | ((self.is_ascii_uppercase() as u8) << 5)
+        *self | (self.is_ascii_uppercase() as u8 * ASCII_CASE_MASK)
+    }
+
+    /// Assumes self is ascii
+    #[inline]
+    pub(crate) fn ascii_change_case_unchecked(&self) -> u8 {
+        *self ^ ASCII_CASE_MASK
     }
 
     /// Checks that two values are an ASCII case-insensitive match.
@@ -234,8 +245,9 @@ pub fn to_ascii_lowercase(&self) -> u8 {
     /// assert!(lowercase_a.eq_ignore_ascii_case(&uppercase_a));
     /// ```
     #[stable(feature = "ascii_methods_on_intrinsics", since = "1.23.0")]
+    #[rustc_const_stable(feature = "const_ascii_methods_on_intrinsics", since = "1.50.0")]
     #[inline]
-    pub fn eq_ignore_ascii_case(&self, other: &u8) -> bool {
+    pub const fn eq_ignore_ascii_case(&self, other: &u8) -> bool {
         self.to_ascii_lowercase() == other.to_ascii_lowercase()
     }