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Auto merge of #150 - ollie27:bigint_to_str, r=cuviper 

bigint: small to_str_radix optimization

Before:
```
test fac_to_string     ... bench:       1,630 ns/iter (+/- 34)
test fib_to_string     ... bench:         359 ns/iter (+/- 11)
test to_str_radix_02   ... bench:       3,097 ns/iter (+/- 19)
test to_str_radix_08   ... bench:       1,146 ns/iter (+/- 38)
test to_str_radix_10   ... bench:       4,248 ns/iter (+/- 36)
test to_str_radix_16   ... bench:         881 ns/iter (+/- 44)
test to_str_radix_36   ... bench:       8,073 ns/iter (+/- 75)
```
After:
```
test fac_to_string     ... bench:       1,492 ns/iter (+/- 20)
test fib_to_string     ... bench:         368 ns/iter (+/- 7)
test to_str_radix_02   ... bench:       2,038 ns/iter (+/- 47)
test to_str_radix_08   ... bench:         812 ns/iter (+/- 9)
test to_str_radix_10   ... bench:       3,919 ns/iter (+/- 40)
test to_str_radix_16   ... bench:         703 ns/iter (+/- 58)
test to_str_radix_36   ... bench:       7,852 ns/iter (+/- 81)
```
This commit is contained in:
Homu 2016-01-13 08:59:01 +09:00
parent 838b4e42b3 d2b23d0f29
commit e65fd4e5b2
1 changed files with 6 additions and 2 deletions
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8
src/bigint.rs
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@ -1483,8 +1483,12 @@ fn to_str_radix_reversed(u: &BigUint, radix: u32) -> Vec<u8> {
// Now convert everything to ASCII digits.
for r in &mut res {
const DIGITS: &'static [u8; 36] = b"0123456789abcdefghijklmnopqrstuvwxyz";
*r = DIGITS[*r as usize];
debug_assert!((*r as u32) < radix);
if *r < 10 {
*r += b'0';
} else {
*r += b'a' - 10;
}
}
res
}