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Diffstat (limited to 'vendor/unic-char-range/src/step.rs')
-rw-r--r-- | vendor/unic-char-range/src/step.rs | 45 |
1 files changed, 45 insertions, 0 deletions
diff --git a/vendor/unic-char-range/src/step.rs b/vendor/unic-char-range/src/step.rs new file mode 100644 index 000000000..1140edd9e --- /dev/null +++ b/vendor/unic-char-range/src/step.rs @@ -0,0 +1,45 @@ +// Copyright 2017 The UNIC Project Developers. +// +// See the COPYRIGHT file at the top-level directory of this distribution. +// +// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or +// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license +// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +use core::char; + +pub const BEFORE_SURROGATE: char = '\u{D7FF}'; +pub const AFTER_SURROGATE: char = '\u{E000}'; + +#[inline] +#[allow(unsafe_code)] +/// Step a character one step towards `char::MAX`. +/// +/// # Safety +/// +/// If the given character is `char::MAX`, the return value is not a valid character. +pub unsafe fn forward(ch: char) -> char { + if ch == BEFORE_SURROGATE { + AFTER_SURROGATE + } else { + char::from_u32_unchecked(ch as u32 + 1) + } +} + +#[inline] +#[allow(unsafe_code)] +/// Step a character one step towards `'\0'`. +/// +/// # Safety +/// +/// If the given character is `'\0'`, this will cause an underflow. +/// (Thus, it will panic in debug mode, undefined behavior in release mode.) +pub unsafe fn backward(ch: char) -> char { + if ch == AFTER_SURROGATE { + BEFORE_SURROGATE + } else { + char::from_u32_unchecked(ch as u32 - 1) + } +} |