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std::str: Use CharOffsetIterator in slice_chars

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This commit is contained in:
blake2-ppc 2013-08-18 22:15:47 +02:00
parent 8931ad9e52
commit 5eff3e1bd9
1 changed files with 16 additions and 15 deletions
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31
src/libstd/str.rs
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@ -1438,23 +1438,24 @@ impl<'self> StrSlice<'self> for &'self str {
/// beyond the last character of the string.
fn slice_chars(&self, begin: uint, end: uint) -> &'self str {
assert!(begin <= end);
// not sure how to use the iterators for this nicely.
let mut position = 0;
let mut count = 0;
let l = self.len();
while count < begin && position < l {
position = self.char_range_at(position).next;
count += 1;
}
if count < begin { fail!("Attempted to begin slice_chars beyond end of string") }
let start_byte = position;
while count < end && position < l {
position = self.char_range_at(position).next;
count += 1;
}
if count < end { fail!("Attempted to end slice_chars beyond end of string") }
let mut begin_byte = None;
let mut end_byte = None;
self.slice(start_byte, position)
// This could be even more efficient by not decoding,
// only finding the char boundaries
for (idx, _) in self.char_offset_iter() {
if count == begin { begin_byte = Some(idx); }
if count == end { end_byte = Some(idx); break; }
count += 1;
}
if end_byte.is_none() && count == end { end_byte = Some(self.len()) }
match (begin_byte, end_byte) {
(None, _) => fail!("slice_chars: `begin` is beyond end of string"),
(_, None) => fail!("slice_chars: `end` is beyond end of string"),
(Some(a), Some(b)) => unsafe { raw::slice_bytes(*self, a, b) }
}
}
/// Returns true if `needle` is a prefix of the string.