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core: Separate failure formatting in str methods slice, slice_to, slice_from 

Use a separate inline-never function to format failure message for
str::slice() errors.

Using strcat's idea, this makes sure no formatting code from failure is
inlined when str::slice() is inlined. The number of `unreachable` being
inlined when usingi `.slice()` drops from 5 to just 1.
This commit is contained in:
root 2014-08-23 12:30:08 +02:00
parent 58bb603ea7
commit b3b7c2e97b
1 changed files with 31 additions and 11 deletions
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42
src/libcore/str.rs
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@ -1705,6 +1705,13 @@ pub trait StrSlice<'a> {
fn utf16_units(&self) -> Utf16CodeUnits<'a>;
}
#[inline(never)]
fn slice_error_fail(s: &str, begin: uint, end: uint) -> ! {
assert!(begin <= end);
fail!("index {} and/or {} in `{}` do not lie on character boundary",
begin, end, s);
}
impl<'a> StrSlice<'a> for &'a str {
#[inline]
fn contains<'a>(&self, needle: &'a str) -> bool {
@ -1808,22 +1815,34 @@ impl<'a> StrSlice<'a> for &'a str {
#[inline]
fn slice(&self, begin: uint, end: uint) -> &'a str {
assert!(self.is_char_boundary(begin) && self.is_char_boundary(end),
"index {} and/or {} in `{}` do not lie on character boundary", begin,
end, *self);
unsafe { raw::slice_bytes(*self, begin, end) }
// is_char_boundary checks that the index is in [0, .len()]
if begin <= end &&
self.is_char_boundary(begin) &&
self.is_char_boundary(end) {
unsafe { raw::slice_unchecked(*self, begin, end) }
} else {
slice_error_fail(*self, begin, end)
}
}
#[inline]
fn slice_from(&self, begin: uint) -> &'a str {
self.slice(begin, self.len())
// is_char_boundary checks that the index is in [0, .len()]
if self.is_char_boundary(begin) {
unsafe { raw::slice_unchecked(*self, begin, self.len()) }
} else {
slice_error_fail(*self, begin, self.len())
}
}
#[inline]
fn slice_to(&self, end: uint) -> &'a str {
assert!(self.is_char_boundary(end), "index {} in `{}` does not lie on \
a character boundary", end, *self);
unsafe { raw::slice_bytes(*self, 0, end) }
// is_char_boundary checks that the index is in [0, .len()]
if self.is_char_boundary(end) {
unsafe { raw::slice_unchecked(*self, 0, end) }
} else {
slice_error_fail(*self, 0, end)
}
}
fn slice_chars(&self, begin: uint, end: uint) -> &'a str {
@ -1898,9 +1917,10 @@ impl<'a> StrSlice<'a> for &'a str {
#[inline]
fn is_char_boundary(&self, index: uint) -> bool {
if index == self.len() { return true; }
if index > self.len() { return false; }
let b = self.as_bytes()[index];
return b < 128u8 || b >= 192u8;
match self.as_bytes().get(index) {
None => false,
Some(&b) => b < 128u8 || b >= 192u8,
}
}
#[inline]