feat: truncate filter
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06e34cf9d5
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@ -146,6 +146,56 @@ pub fn trim<T: Render>(expr: &T) -> Trim<T> {
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Trim(expr)
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}
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pub struct Truncate<'a, T>(&'a T, usize);
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impl<'a, T: Render> Render for Truncate<'a, T> {
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#[inline]
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fn render(&self, b: &mut Buffer) -> Result<(), RenderError> {
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let old_len = b.len();
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self.0.render(b)?;
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truncate_impl(b, old_len, self.1)
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}
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#[inline]
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fn render_escaped(&self, b: &mut Buffer) -> Result<(), RenderError> {
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let old_len = b.len();
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self.0.render_escaped(b)?;
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truncate_impl(b, old_len, self.1)
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}
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}
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fn truncate_impl(
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b: &mut Buffer,
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old_len: usize,
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limit: usize,
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) -> Result<(), RenderError> {
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let mut pos = old_len + limit;
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if b.len() > pos {
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let tmp = b.as_str();
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while !tmp.is_char_boundary(pos) {
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pos += 1;
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}
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unsafe { b._set_len(pos) };
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b.push_str("...");
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Ok(())
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} else if b.len() >= old_len {
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Ok(())
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} else {
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Err(RenderError::new("buffer size shrinked while rendering"))
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}
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}
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/// Limit length of rendered contents, appends '...' if truncated
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#[inline]
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pub fn truncate<T: Render>(expr: &T, mut limit: usize) -> Truncate<T> {
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// SAFETY: since `buf.len() <= isize::MAX`, length of rendered contents never
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// overflows isize::MAX. If limit > isize::MAX, then truncation never happens
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limit &= std::usize::MAX >> 1;
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Truncate(expr, limit)
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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