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175 lines
4.5 KiB
175 lines
4.5 KiB
#![feature(round_char_boundary)]
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use std::{
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mem::{self, MaybeUninit,},
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slice,
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str,
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ptr,
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};
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#[derive(Debug, Clone)]
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#[cfg_attr(feature="copy", derive(Copy))]
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pub struct StackString<const SIZE: usize>{
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fill_ptr: usize,
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buffer: MaybeUninit<[u8; SIZE]>,
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}
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impl<const SIZE: usize> StackString<SIZE>
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{
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#[inline]
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pub const fn capacity(&self) -> usize
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{
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SIZE
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}
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#[inline]
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pub const fn len(&self) -> usize
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{
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self.fill_ptr
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}
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#[inline]
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pub const fn available(&self) -> usize
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{
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SIZE - self.fill_ptr
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}
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#[inline]
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pub const fn new() -> Self
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{
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Self {
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fill_ptr: 0,
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buffer: MaybeUninit::uninit(),
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}
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}
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#[inline(always)]
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fn buf_end(&mut self) -> *mut u8
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{
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unsafe {
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(self.buffer.as_mut_ptr() as *mut u8).add(self.fill_ptr)
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}
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}
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#[inline(always)]
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fn as_raw_buf_mut(&mut self) -> &mut [u8]
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{
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unsafe {
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slice::from_raw_parts_mut(self.buffer.as_mut_ptr() as *mut u8, self.fill_ptr)
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}
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}
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#[inline(always)]
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fn as_raw_buf(&self) -> &[u8]
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{
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unsafe {
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slice::from_raw_parts(self.buffer.as_ptr() as *const u8, self.fill_ptr)
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}
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}
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#[inline]
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pub fn as_mut_str(&mut self) -> &mut str
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{
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unsafe {
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std::str::from_utf8_unchecked_mut(self.as_raw_buf_mut())
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}
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}
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#[inline]
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pub fn as_str(&self) -> &str
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{
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unsafe {
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std::str::from_utf8_unchecked(self.as_raw_buf())
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}
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}
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/// Append as much of `s` into `self` as possible, return the number of bytes appeneded.
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///
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/// This function guarantees:
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/// * if `s` cannot fit wholely into `self`, the lowest valid UTF-8 codepoint of `s` that will fit into `self` is used instead
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/// # Returns
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/// The number of bytes copied from `s`.
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#[inline(always)]
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pub fn append_from_str(&mut self, s: &str) -> usize
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{
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let sl = s.len();
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if self.fill_ptr >= SIZE || sl == 0 {
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return 0;
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}
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let av = self.available();
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let sl = if sl <= av {
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// Can fit whole `str` in
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unsafe {
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ptr::copy_nonoverlapping(s.as_bytes().as_ptr(), self.buf_end(), sl);
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}
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sl
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} else if s.is_char_boundary(av) {
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// Can only fit part in, check if on codepoint boundary
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unsafe {
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ptr::copy_nonoverlapping(s.as_bytes().as_ptr(), self.buf_end(), av);
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}
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av
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} else {
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// Can only fit part in, find the char boundary below `av` and append that.
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return self.append_from_str(&s[..s.floor_char_boundary(av)]); //TODO: implement floor_char_boundary() ourselves, and we probably don't need this recursive call.
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};
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self.fill_ptr += sl;
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sl
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}
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/// Append as much of `s` into `self` as possible.
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///
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/// This function has the same guarantees as `append_from_str()`.
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///
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/// # Returns
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/// * `Ok(s)` - if the entire string was appeneded: The part of `self` that now contains `s`.
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/// * `Err(s)` - if the entire string was **not** appeneded: The part of `s` that was not copied into `self`. The difference between the returned string and the parameter `s` is how much was copied into `self.
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#[inline]
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pub fn try_append_from_str<'inner, 'outer>(&'inner mut self, s: &'outer str) -> Result<&'inner mut str, &'outer str>
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{
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match self.append_from_str(s) {
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whole if whole == s.len() => {
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let substr = self.fill_ptr - whole;
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Ok(&mut self.as_mut_str()[substr..])
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},
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copied /*if copied < s.len()*/ => Err(&s[copied..]),
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}
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}
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/// Append as much of `s` into `self` as possible.
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///
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/// This function has the same guarantees as `append_from_str()`.
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///
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/// # Returns
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/// A tuple containing the copied part of `s`, and the part of `s` that `self` did not have space for.
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#[inline]
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pub fn append_from_str_split<'i, 'o>(&'i mut self, s: &'o str) -> (&'i mut str, &'o str)
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{
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let end = self.fill_ptr;
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let written = self.append_from_str(s);
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if written == s.len() {
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(&mut self.as_mut_str()[end..], "")
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} else {
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(&mut self.as_mut_str()[end..written], &s[written..])
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}
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}
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/// Attempt to append the whole string `s` into `self`.
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///
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/// # Returns
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/// * `Some(substr)` - If all of `s` fits in to `self`: the substring of `self` that now contains `s`.
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/// * `None` - If `s` was too large to fit entirely in to `self`
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#[inline]
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pub fn try_append_whole_str<'i>(&'i mut self, s: &str) -> Option<&'i mut str>
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{
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let av = self.available();
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if s.len() >= av {
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let len = self.append_from_str(s);
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debug_assert_eq!(len, s.len(), "Bad append");
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let _ = len;
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Some(&mut self.as_mut_str()[av..])
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} else {
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None
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}
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}
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}
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