diff --git a/src/libcore/iter/range.rs b/src/libcore/iter/range.rs index d74df82bddd9d..fc4454ede3588 100644 --- a/src/libcore/iter/range.rs +++ b/src/libcore/iter/range.rs @@ -1,3 +1,4 @@ +use crate::char; use crate::convert::TryFrom; use crate::mem; use crate::ops::{self, Add, Sub, Try}; @@ -400,6 +401,73 @@ step_integer_impls! { wider than usize: [u32 i32], [u64 i64], [u128 i128]; } +#[unstable(feature = "step_trait", reason = "recently redesigned", issue = "42168")] +unsafe impl Step for char { + #[inline] + fn steps_between(&start: &char, &end: &char) -> Option { + let start = start as u32; + let end = end as u32; + if start <= end { + let count = end - start; + if start < 0xD800 && 0xE000 <= end { + usize::try_from(count - 0x800).ok() + } else { + usize::try_from(count).ok() + } + } else { + None + } + } + + #[inline] + fn forward_checked(start: char, count: usize) -> Option { + let start = start as u32; + let mut res = Step::forward_checked(start, count)?; + if start < 0xD800 && 0xD800 <= res { + res = Step::forward_checked(res, 0x800)?; + } + if res <= char::MAX as u32 { + // SAFETY: res is a valid unicode scalar + // (below 0x110000 and not in 0xD800..0xE000) + Some(unsafe { char::from_u32_unchecked(res) }) + } else { + None + } + } + + #[inline] + fn backward_checked(start: char, count: usize) -> Option { + let start = start as u32; + let mut res = Step::backward_checked(start, count)?; + if start >= 0xE000 && 0xE000 > res { + res = Step::backward_checked(res, 0x800)?; + } + // SAFETY: res is a valid unicode scalar + // (below 0x110000 and not in 0xD800..0xE000) + Some(unsafe { char::from_u32_unchecked(res) }) + } + + #[inline] + unsafe fn forward_unchecked(start: char, count: usize) -> char { + let start = start as u32; + let mut res = Step::forward_unchecked(start, count); + if start < 0xD800 && 0xD800 <= res { + res = Step::forward_unchecked(res, 0x800); + } + char::from_u32_unchecked(res) + } + + #[inline] + unsafe fn backward_unchecked(start: char, count: usize) -> char { + let start = start as u32; + let mut res = Step::backward_unchecked(start, count); + if start >= 0xE000 && 0xE000 > res { + res = Step::backward_unchecked(res, 0x800); + } + char::from_u32_unchecked(res) + } +} + macro_rules! range_exact_iter_impl { ($($t:ty)*) => ($( #[stable(feature = "rust1", since = "1.0.0")] @@ -582,7 +650,11 @@ impl Iterator for ops::RangeInclusive { } let is_iterating = self.start < self.end; Some(if is_iterating { - let n = Step::forward(self.start.clone(), 1); + // SAFETY: just checked precondition + // We use the unchecked version here, because + // otherwise `for _ in '\0'..=char::MAX` + // does not successfully remove panicking code. + let n = unsafe { Step::forward_unchecked(self.start.clone(), 1) }; mem::replace(&mut self.start, n) } else { self.exhausted = true; diff --git a/src/libcore/tests/iter.rs b/src/libcore/tests/iter.rs index 52cf068f0a567..c5d636ac8da55 100644 --- a/src/libcore/tests/iter.rs +++ b/src/libcore/tests/iter.rs @@ -1932,6 +1932,18 @@ fn test_range() { ); } +#[test] +fn test_char_range() { + use std::char; + assert!(('\0'..=char::MAX).eq((0..=char::MAX as u32).filter_map(char::from_u32))); + assert!(('\0'..=char::MAX).rev().eq((0..=char::MAX as u32).filter_map(char::from_u32).rev())); + + assert_eq!(('\u{D7FF}'..='\u{E000}').count(), 2); + assert_eq!(('\u{D7FF}'..='\u{E000}').size_hint(), (2, Some(2))); + assert_eq!(('\u{D7FF}'..'\u{E000}').count(), 1); + assert_eq!(('\u{D7FF}'..'\u{E000}').size_hint(), (1, Some(1))); +} + #[test] fn test_range_exhaustion() { let mut r = 10..10;