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expose char::encode_utf8_raw for libstd

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This commit is contained in:
Ralf Jung 2020-05-30 11:49:31 +02:00
parent 52ed89ae8c
commit 72d85db6ee
2 changed files with 63 additions and 40 deletions
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99
src/libcore/char/methods.rs
View File

@ -593,16 +593,7 @@ impl char {
#[stable(feature = "rust1", since = "1.0.0")]
#[inline]
pub fn len_utf8(self) -> usize {
let code = self as u32;
if code < MAX_ONE_B {
1
} else if code < MAX_TWO_B {
2
} else if code < MAX_THREE_B {
3
} else {
4
}
len_utf8(self as u32)
}
/// Returns the number of 16-bit code units this `char` would need if
@ -670,36 +661,7 @@ impl char {
#[stable(feature = "unicode_encode_char", since = "1.15.0")]
#[inline]
pub fn encode_utf8(self, dst: &mut [u8]) -> &mut str {
let code = self as u32;
let len = self.len_utf8();
match (len, &mut dst[..]) {
(1, [a, ..]) => {
*a = code as u8;
}
(2, [a, b, ..]) => {
*a = (code >> 6 & 0x1F) as u8 | TAG_TWO_B;
*b = (code & 0x3F) as u8 | TAG_CONT;
}
(3, [a, b, c, ..]) => {
*a = (code >> 12 & 0x0F) as u8 | TAG_THREE_B;
*b = (code >> 6 & 0x3F) as u8 | TAG_CONT;
*c = (code & 0x3F) as u8 | TAG_CONT;
}
(4, [a, b, c, d, ..]) => {
*a = (code >> 18 & 0x07) as u8 | TAG_FOUR_B;
*b = (code >> 12 & 0x3F) as u8 | TAG_CONT;
*c = (code >> 6 & 0x3F) as u8 | TAG_CONT;
*d = (code & 0x3F) as u8 | TAG_CONT;
}
_ => panic!(
"encode_utf8: need {} bytes to encode U+{:X}, but the buffer has {}",
len,
code,
dst.len(),
),
};
// SAFETY: We just wrote UTF-8 content in, so converting to str is fine.
unsafe { from_utf8_unchecked_mut(&mut dst[..len]) }
encode_utf8_raw(self as u32, dst)
}
/// Encodes this character as UTF-16 into the provided `u16` buffer,
@ -1673,3 +1635,60 @@ impl char {
}
}
}
#[inline]
fn len_utf8(code: u32) -> usize {
if code < MAX_ONE_B {
1
} else if code < MAX_TWO_B {
2
} else if code < MAX_THREE_B {
3
} else {
4
}
}
/// 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 can be called on codepoints in the surrogate range.
///
/// # Panics
///
/// Panics if the buffer is not large enough.
/// A buffer of length four is large enough to encode any `char`.
#[unstable(feature = "char_internals", reason = "exposed only for libstd", issue = "none")]
#[doc(hidden)]
#[inline]
pub fn encode_utf8_raw(code: u32, dst: &mut [u8]) -> &mut str {
let len = len_utf8(code);
match (len, &mut dst[..]) {
(1, [a, ..]) => {
*a = code as u8;
}
(2, [a, b, ..]) => {
*a = (code >> 6 & 0x1F) as u8 | TAG_TWO_B;
*b = (code & 0x3F) as u8 | TAG_CONT;
}
(3, [a, b, c, ..]) => {
*a = (code >> 12 & 0x0F) as u8 | TAG_THREE_B;
*b = (code >> 6 & 0x3F) as u8 | TAG_CONT;
*c = (code & 0x3F) as u8 | TAG_CONT;
}
(4, [a, b, c, d, ..]) => {
*a = (code >> 18 & 0x07) as u8 | TAG_FOUR_B;
*b = (code >> 12 & 0x3F) as u8 | TAG_CONT;
*c = (code >> 6 & 0x3F) as u8 | TAG_CONT;
*d = (code & 0x3F) as u8 | TAG_CONT;
}
_ => panic!(
"encode_utf8: need {} bytes to encode U+{:X}, but the buffer has {}",
len,
code,
dst.len(),
),
};
// SAFETY: We just wrote UTF-8 content in, so converting to str is fine.
unsafe { from_utf8_unchecked_mut(&mut dst[..len]) }
}

4
src/libcore/char/mod.rs
View File

@ -37,6 +37,10 @@ pub use self::decode::{decode_utf16, DecodeUtf16, DecodeUtf16Error};
#[stable(feature = "unicode_version", since = "1.45.0")]
pub use crate::unicode::UNICODE_VERSION;
// perma-unstable re-exports
#[unstable(feature = "char_internals", reason = "exposed only for libstd", issue = "none")]
pub use self::methods::encode_utf8_raw;
use crate::fmt::{self, Write};
use crate::iter::FusedIterator;