65 lines
2.2 KiB
Rust
65 lines
2.2 KiB
Rust
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//! We maintain invariant that all internal strings use `\n` as line separator.
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//! This module does line ending conversion and detection (so that we can
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//! convert back to `\r\n` on the way out).
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#[derive(Debug, Clone, Copy, PartialEq, Eq, PartialOrd, Ord, Hash)]
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pub(crate) enum LineEndings {
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Unix,
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Dos,
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}
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impl LineEndings {
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/// Replaces `\r\n` with `\n` in-place in `src`.
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pub(crate) fn normalize(src: String) -> (String, LineEndings) {
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if !src.as_bytes().contains(&b'\r') {
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return (src, LineEndings::Unix);
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}
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// We replace `\r\n` with `\n` in-place, which doesn't break utf-8 encoding.
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// While we *can* call `as_mut_vec` and do surgery on the live string
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// directly, let's rather steal the contents of `src`. This makes the code
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// safe even if a panic occurs.
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let mut buf = src.into_bytes();
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let mut gap_len = 0;
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let mut tail = buf.as_mut_slice();
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loop {
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let idx = match find_crlf(&tail[gap_len..]) {
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None => tail.len(),
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Some(idx) => idx + gap_len,
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};
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tail.copy_within(gap_len..idx, 0);
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tail = &mut tail[idx - gap_len..];
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if tail.len() == gap_len {
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break;
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}
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gap_len += 1;
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}
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// Account for removed `\r`.
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// After `set_len`, `buf` is guaranteed to contain utf-8 again.
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let new_len = buf.len() - gap_len;
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let src = unsafe {
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buf.set_len(new_len);
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String::from_utf8_unchecked(buf)
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};
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return (src, LineEndings::Dos);
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fn find_crlf(src: &[u8]) -> Option<usize> {
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let mut search_idx = 0;
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while let Some(idx) = find_cr(&src[search_idx..]) {
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if src[search_idx..].get(idx + 1) != Some(&b'\n') {
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search_idx += idx + 1;
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continue;
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}
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return Some(search_idx + idx);
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}
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None
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}
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fn find_cr(src: &[u8]) -> Option<usize> {
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src.iter().enumerate().find_map(|(idx, &b)| if b == b'\r' { Some(idx) } else { None })
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}
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}
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}
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