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)
+    }
+}