Add trim filter
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31bbcaebc8
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fcde448751
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@ -1,6 +1,9 @@
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//! Build-in filters
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// TODO: performance improvement
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use std::fmt;
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use std::ptr;
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use super::{Buffer, Render, RenderError};
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@ -86,6 +89,60 @@ pub fn lower<T: Render>(expr: &T) -> Lower<T> {
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Lower(expr)
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}
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pub struct Trim<'a, T>(&'a T);
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impl<'a, T: Render> Render for Trim<'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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trim_impl(b, old_len);
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Ok(())
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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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trim_impl(b, old_len);
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Ok(())
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}
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}
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fn trim_impl(b: &mut Buffer, old_len: usize) {
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debug_assert!(b.len() >= old_len);
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let new_contents = &b.as_str()[old_len..];
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let trimmed = new_contents.trim();
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let trimmed_len = trimmed.len();
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if new_contents.len() != trimmed_len {
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// performs inplace trimming
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if new_contents.as_ptr() != trimmed.as_ptr() {
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debug_assert!(new_contents.as_ptr() < trimmed.as_ptr());
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let offset = trimmed.as_ptr() as usize - new_contents.as_ptr() as usize;
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unsafe {
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ptr::copy(
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b.as_mut_ptr().add(old_len + offset),
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b.as_mut_ptr().add(old_len),
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trimmed_len,
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);
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}
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}
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debug_assert!(b.capacity() >= old_len + trimmed_len);
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unsafe {
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b._set_len(old_len + trimmed_len);
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}
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}
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}
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/// convert the rendered contents to lowercase
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#[inline]
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pub fn trim<T: Render>(expr: &T) -> Trim<T> {
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Trim(expr)
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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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@ -104,4 +161,23 @@ mod tests {
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lower(&"<h1>TITLE</h1>").render_escaped(&mut buf).unwrap();
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assert_eq!(buf.as_str(), "<h1>title</h1>");
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}
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#[test]
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fn trim_test() {
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let mut buf = Buffer::new();
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trim(&" hello ").render(&mut buf).unwrap();
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trim(&"hello ").render(&mut buf).unwrap();
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trim(&" hello").render(&mut buf).unwrap();
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assert_eq!(buf.as_str(), "hellohellohello");
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let mut buf = Buffer::new();
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trim(&"hello ").render(&mut buf).unwrap();
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trim(&" hello").render(&mut buf).unwrap();
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trim(&"hello").render(&mut buf).unwrap();
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assert_eq!(buf.as_str(), "hellohellohello");
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let mut buf = Buffer::new();
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trim(&" hello").render(&mut buf).unwrap();
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assert_eq!(buf.as_str(), "hello");
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}
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}
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