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uniq: add more fast-paths to avoid work

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This commit is contained in:
Simon Vandel Sillesen 2018-07-12 17:00:06 +02:00
parent 3288fa2cd2
commit 781c9236e1
1 changed files with 15 additions and 2 deletions
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17
src/uniq/uniq.rs
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@ -113,6 +113,19 @@ impl Uniq {
let slice_start = self.slice_start.unwrap_or(0); let slice_start = self.slice_start.unwrap_or(0);
let slice_stop = self.slice_stop.unwrap_or(len); let slice_stop = self.slice_stop.unwrap_or(len);
if len > 0 { if len > 0 {
// fast path: avoid doing any work if there is no need to skip or map to lower-case
if !self.ignore_case && slice_start == 0 && slice_stop == len {
return Box::new(fields_to_check.chars());
}
// fast path: avoid skipping
if self.ignore_case && slice_start == 0 && slice_stop == len {
return Box::new(fields_to_check.chars().map(|c| match c {
'a'...'z' => ((c as u8) - 32) as char,
_ => c,
}));
}
// fast path: we can avoid mapping chars to upper-case, if we don't want to ignore the case // fast path: we can avoid mapping chars to upper-case, if we don't want to ignore the case
if !self.ignore_case { if !self.ignore_case {
return Box::new(fields_to_check.chars().skip(slice_start).take(slice_stop)); return Box::new(fields_to_check.chars().skip(slice_start).take(slice_stop));
@ -123,8 +136,8 @@ impl Uniq {
.chars() .chars()
.skip(slice_start) .skip(slice_start)
.take(slice_stop) .take(slice_stop)
.map(move |c| match c { .map(|c| match c {
'a'...'z' if self.ignore_case => ((c as u8) - 32) as char, 'a'...'z' => ((c as u8) - 32) as char,
_ => c, _ => c,
}), }),
) )