| @@ -269,8 +269,7 @@ impl str { |
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#[stable(feature = "rust1", since = "1.0.0")] |
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#[inline] |
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pub fn replace<P: Pattern>(&self, from: P, to: &str) -> String { |
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-// Fast path for ASCII to ASCII case. |
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- |
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+// Fast path for replacing a single ASCII character with another. |
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if let Some(from_byte) = match from.as_utf8_pattern() { |
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Some(Utf8Pattern::StringPattern([from_byte])) => Some(*from_byte), |
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Some(Utf8Pattern::CharPattern(c)) => c.as_ascii().map(|ascii_char |
| @@ -280,8 +279,13 @@ impl str { |
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return unsafe { replace_ascii(self.as_bytes(), from_byte, *to_byte) }; |
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} |
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} |
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- |
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-let mut result = String::new(); |
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+// Set result capacity to self.len() when from.len() <= to.len() |
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+let default_capacity = match from.as_utf8_pattern() { |
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+Some(Utf8Pattern::StringPattern(s)) if s.len() <= to.len() => self.len(), |
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+Some(Utf8Pattern::CharPattern(c)) if c.len_utf8() <= to.len() => self.len(), |
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+ _ => 0, |
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+}; |
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+let mut result = String::with_capacity(default_capacity); |
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let mut last_end = 0; |
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for (start, part) in self.match_indices(from) { |
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result.push_str(unsafe { self.get_unchecked(last_end..start) }); |