diff options
| -rw-r--r-- | library/core/src/char/methods.rs | 60 | ||||
| -rw-r--r-- | library/core/src/lib.rs | 1 |
2 files changed, 36 insertions, 25 deletions
diff --git a/library/core/src/char/methods.rs b/library/core/src/char/methods.rs index 092d427ecea..23d61e368ce 100644 --- a/library/core/src/char/methods.rs +++ b/library/core/src/char/methods.rs @@ -638,8 +638,7 @@ impl char { #[rustc_const_stable(feature = "const_char_len_utf", since = "1.52.0")] #[inline] pub const fn len_utf16(self) -> usize { - let ch = self as u32; - if (ch & 0xFFFF) == ch { 1 } else { 2 } + len_utf16(self as u32) } /// Encodes this character as UTF-8 into the provided byte buffer, @@ -709,8 +708,9 @@ impl char { /// '𝕊'.encode_utf16(&mut b); /// ``` #[stable(feature = "unicode_encode_char", since = "1.15.0")] + #[rustc_const_unstable(feature = "const_char_encode_utf16", issue = "130660")] #[inline] - pub fn encode_utf16(self, dst: &mut [u16]) -> &mut [u16] { + pub const fn encode_utf16(self, dst: &mut [u16]) -> &mut [u16] { encode_utf16_raw(self as u32, dst) } @@ -1745,7 +1745,12 @@ const fn len_utf8(code: u32) -> usize { } } -/// Encodes a raw u32 value as UTF-8 into the provided byte buffer, +#[inline] +const fn len_utf16(code: u32) -> usize { + if (code & 0xFFFF) == code { 1 } else { 2 } +} + +/// Encodes a raw `u32` value as UTF-8 into the provided byte buffer, /// and then returns the subslice of the buffer that contains the encoded character. /// /// Unlike `char::encode_utf8`, this method also handles codepoints in the surrogate range. @@ -1799,7 +1804,7 @@ pub const fn encode_utf8_raw(code: u32, dst: &mut [u8]) -> &mut [u8] { unsafe { slice::from_raw_parts_mut(dst.as_mut_ptr(), len) } } -/// Encodes a raw u32 value as UTF-16 into the provided `u16` buffer, +/// Encodes a raw `u32` value as UTF-16 into the provided `u16` buffer, /// and then returns the subslice of the buffer that contains the encoded character. /// /// Unlike `char::encode_utf16`, this method also handles codepoints in the surrogate range. @@ -1810,28 +1815,33 @@ pub const fn encode_utf8_raw(code: u32, dst: &mut [u8]) -> &mut [u8] { /// Panics if the buffer is not large enough. /// A buffer of length 2 is large enough to encode any `char`. #[unstable(feature = "char_internals", reason = "exposed only for libstd", issue = "none")] +#[rustc_const_unstable(feature = "const_char_encode_utf16", issue = "130660")] #[doc(hidden)] #[inline] -pub fn encode_utf16_raw(mut code: u32, dst: &mut [u16]) -> &mut [u16] { - // SAFETY: each arm checks whether there are enough bits to write into - unsafe { - if (code & 0xFFFF) == code && !dst.is_empty() { - // The BMP falls through - *dst.get_unchecked_mut(0) = code as u16; - slice::from_raw_parts_mut(dst.as_mut_ptr(), 1) - } else if dst.len() >= 2 { - // Supplementary planes break into surrogates. +pub const fn encode_utf16_raw(mut code: u32, dst: &mut [u16]) -> &mut [u16] { + const fn panic_at_const(_code: u32, _len: usize, _dst_len: usize) { + // Note that we cannot format in constant expressions. + panic!("encode_utf16: buffer does not have enough bytes to encode code point"); + } + fn panic_at_rt(code: u32, len: usize, dst_len: usize) { + panic!( + "encode_utf16: need {len} bytes to encode U+{code:04X} but buffer has just {dst_len}", + ); + } + let len = len_utf16(code); + match (len, &mut *dst) { + (1, [a, ..]) => { + *a = code as u16; + } + (2, [a, b, ..]) => { code -= 0x1_0000; - *dst.get_unchecked_mut(0) = 0xD800 | ((code >> 10) as u16); - *dst.get_unchecked_mut(1) = 0xDC00 | ((code as u16) & 0x3FF); - slice::from_raw_parts_mut(dst.as_mut_ptr(), 2) - } else { - panic!( - "encode_utf16: need {} units to encode U+{:X}, but the buffer has {}", - char::from_u32_unchecked(code).len_utf16(), - code, - dst.len(), - ) + + *a = (code >> 10) as u16 | 0xD800; + *b = (code & 0x3FF) as u16 | 0xDC00; } - } + // FIXME(const-hack): We would prefer to have streamlined panics when formatters become const-friendly. + _ => const_eval_select((code, len, dst.len()), panic_at_const, panic_at_rt), + }; + // SAFETY: `<&mut [u16]>::as_mut_ptr` is guaranteed to return a valid pointer and `len` has been tested to be within bounds. + unsafe { slice::from_raw_parts_mut(dst.as_mut_ptr(), len) } } diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs index f25f6922bca..536a1a83dac 100644 --- a/library/core/src/lib.rs +++ b/library/core/src/lib.rs @@ -119,6 +119,7 @@ #![feature(const_bigint_helper_methods)] #![feature(const_black_box)] #![feature(const_cell_into_inner)] +#![feature(const_char_encode_utf16)] #![feature(const_char_encode_utf8)] #![feature(const_eval_select)] #![feature(const_exact_div)] |