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|
use std::char;
use std::char::DecodeUtf16;
use std::num::NonZeroU16;
use crate::util::BYTE_SHIFT;
use crate::util::CONT_MASK;
use crate::util::CONT_TAG;
use super::CodePoints;
use super::Result;
const MIN_HIGH_SURROGATE: u16 = 0xD800;
const MIN_LOW_SURROGATE: u16 = 0xDC00;
const MIN_SURROGATE_CODE: u32 = (u16::MAX as u32) + 1;
macro_rules! static_assert {
( $condition:expr ) => {
const _: () = assert!($condition, "static assertion failed");
};
}
pub(in super::super) struct DecodeWide<I>
where
I: Iterator<Item = u16>,
{
iter: DecodeUtf16<I>,
code_point: u32,
shift: u8,
}
impl<I> DecodeWide<I>
where
I: Iterator<Item = u16>,
{
pub(in super::super) fn new<S>(string: S) -> Self
where
S: IntoIterator<IntoIter = I, Item = I::Item>,
{
Self {
iter: char::decode_utf16(string),
code_point: 0,
shift: 0,
}
}
}
impl<I> Iterator for DecodeWide<I>
where
I: Iterator<Item = u16>,
{
type Item = u8;
fn next(&mut self) -> Option<Self::Item> {
if let Some(shift) = self.shift.checked_sub(BYTE_SHIFT) {
self.shift = shift;
return Some(
((self.code_point >> self.shift) as u8 & CONT_MASK) | CONT_TAG,
);
}
self.code_point = self
.iter
.next()?
.map(Into::into)
.unwrap_or_else(|x| x.unpaired_surrogate().into());
macro_rules! decode {
( $tag:expr ) => {
Some((self.code_point >> self.shift) as u8 | $tag)
};
}
macro_rules! try_decode {
( $tag:expr , $upper_bound:expr ) => {
if self.code_point < $upper_bound {
return decode!($tag);
}
self.shift += BYTE_SHIFT;
};
}
try_decode!(0, 0x80);
try_decode!(0xC0, 0x800);
try_decode!(0xE0, MIN_SURROGATE_CODE);
decode!(0xF0)
}
fn size_hint(&self) -> (usize, Option<usize>) {
let (low, high) = self.iter.size_hint();
let shift = self.shift.into();
(
low.saturating_add(shift),
high.and_then(|x| x.checked_mul(4))
.and_then(|x| x.checked_add(shift)),
)
}
}
struct EncodeWide<I>
where
I: Iterator<Item = u8>,
{
iter: CodePoints<I>,
surrogate: Option<NonZeroU16>,
}
impl<I> EncodeWide<I>
where
I: Iterator<Item = u8>,
{
pub(in super::super) fn new<S>(string: S) -> Self
where
S: IntoIterator<IntoIter = I, Item = I::Item>,
{
Self {
iter: CodePoints::new(string),
surrogate: None,
}
}
}
impl<I> Iterator for EncodeWide<I>
where
I: Iterator<Item = u8>,
{
type Item = Result<u16>;
fn next(&mut self) -> Option<Self::Item> {
if let Some(surrogate) = self.surrogate.take() {
return Some(Ok(surrogate.get()));
}
self.iter.next().map(|code_point| {
code_point.map(|code_point| {
code_point
.checked_sub(MIN_SURROGATE_CODE)
.map(|offset| {
static_assert!(MIN_LOW_SURROGATE != 0);
self.surrogate = Some(unsafe {
NonZeroU16::new_unchecked(
(offset & 0x3FF) as u16 | MIN_LOW_SURROGATE,
)
});
(offset >> 10) as u16 | MIN_HIGH_SURROGATE
})
.unwrap_or(code_point as u16)
})
})
}
fn size_hint(&self) -> (usize, Option<usize>) {
let (low, high) = self.iter.inner_size_hint();
let additional = self.surrogate.is_some().into();
(
(low.saturating_add(2) / 3).saturating_add(additional),
high.and_then(|x| x.checked_add(additional)),
)
}
}
pub(in super::super) fn encode_wide(
string: &[u8],
) -> impl '_ + Iterator<Item = Result<u16>> {
EncodeWide::new(string.iter().copied())
}
|
