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auto merge of #7696 : glinscott/rust/utf8_perf, r=cmr

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Moves multibyte code to it's own function to make char_range_at
easier to inline, and faster for single and multibyte chars.

Benchmarked reading example.json 100 times, 1.18s before, 1.08s
after.

Also, optimize str::is_utf8 for the single and multibyte case
Before:
is_utf8_ascii:          272.355162 ms
is_utf8_multibyte:      167.337334 ms

After:
is_utf8_ascii:          218.088049 ms
is_utf8_multibyte:      134.836722 ms
This commit is contained in:
bors 2013-07-12 03:46:41 -07:00
commit f67935257b
3 changed files with 111 additions and 36 deletions
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112
src/libstd/str.rs
View File

@ -596,17 +596,25 @@ pub fn is_utf8(v: &[u8]) -> bool {
let mut i = 0u;
let total = v.len();
while i < total {
let mut chsize = utf8_char_width(v[i]);
if chsize == 0u { return false; }
if i + chsize > total { return false; }
i += 1u;
while chsize > 1u {
if v[i] & 192u8 != TAG_CONT_U8 { return false; }
if v[i] < 128u8 {
i += 1u;
chsize -= 1u;
} else {
let w = utf8_char_width(v[i]);
if w == 0u { return false; }
let nexti = i + w;
if nexti > total { return false; }
if v[i + 1] & 192u8 != TAG_CONT_U8 { return false; }
if w > 2 {
if v[i + 2] & 192u8 != TAG_CONT_U8 { return false; }
if w > 3 && (v[i + 3] & 192u8 != TAG_CONT_U8) { return false; }
}
i = nexti;
}
}
return true;
true
}
/// Determines if a vector of `u16` contains valid UTF-16
@ -722,17 +730,29 @@ pub fn count_bytes<'b>(s: &'b str, start: uint, n: uint) -> uint {
end - start
}
// https://tools.ietf.org/html/rfc3629
static UTF8_CHAR_WIDTH: [u8, ..256] = [
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, // 0x1F
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, // 0x3F
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, // 0x5F
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,
1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1, // 0x7F
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 0x9F
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,
0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, // 0xBF
2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,
2,2,2,2,2,2,2,2,2,2,2,2,2,2,2,2, // 0xDF
3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3, // 0xEF
4,4,4,4,4,0,0,0,0,0,0,0,0,0,0,0, // 0xFF
];
/// Given a first byte, determine how many bytes are in this UTF-8 character
pub fn utf8_char_width(b: u8) -> uint {
let byte: uint = b as uint;
if byte < 128u { return 1u; }
// Not a valid start byte
if byte < 192u { return 0u; }
if byte < 224u { return 2u; }
if byte < 240u { return 3u; }
if byte < 248u { return 4u; }
if byte < 252u { return 5u; }
return 6u;
return UTF8_CHAR_WIDTH[b] as uint;
}
#[allow(missing_doc)]
@ -1714,26 +1734,29 @@ impl<'self> StrSlice<'self> for &'self str {
* If `i` is greater than or equal to the length of the string.
* If `i` is not the index of the beginning of a valid UTF-8 character.
*/
#[inline]
fn char_range_at(&self, i: uint) -> CharRange {
let b0 = self[i];
let w = utf8_char_width(b0);
assert!((w != 0u));
if w == 1u { return CharRange {ch: b0 as char, next: i + 1u}; }
let mut val = 0u;
let end = i + w;
let mut i = i + 1u;
while i < end {
let byte = self[i];
assert_eq!(byte & 192u8, TAG_CONT_U8);
val <<= 6u;
val += (byte & 63u8) as uint;
i += 1u;
if (self[i] < 128u8) {
return CharRange {ch: self[i] as char, next: i + 1 };
}
// Clunky way to get the right bits from the first byte. Uses two shifts,
// the first to clip off the marker bits at the left of the byte, and then
// a second (as uint) to get it to the right position.
val += ((b0 << ((w + 1u) as u8)) as uint) << ((w - 1u) * 6u - w - 1u);
return CharRange {ch: val as char, next: i};
// Multibyte case is a fn to allow char_range_at to inline cleanly
fn multibyte_char_range_at(s: &str, i: uint) -> CharRange {
let mut val = s[i] as uint;
let w = UTF8_CHAR_WIDTH[val] as uint;
assert!((w != 0));
// First byte is special, only want bottom 5 bits for width 2, 4 bits
// for width 3, and 3 bits for width 4
val &= 0x7Fu >> w;
val = (val << 6) | (s[i + 1] & 63u8) as uint;
if w > 2 { val = (val << 6) | (s[i + 2] & 63u8) as uint; }
if w > 3 { val = (val << 6) | (s[i + 3] & 63u8) as uint; }
return CharRange {ch: val as char, next: i + w};
}
return multibyte_char_range_at(*self, i);
}
/// Plucks the character starting at the `i`th byte of a string
@ -2430,7 +2453,11 @@ mod tests {
fn test_push_char() {
let mut data = ~"ประเทศไทย中";
data.push_char('华');
assert_eq!(~"ประเทศไทย中华", data);
data.push_char('b'); // 1 byte
data.push_char('¢'); // 2 byte
data.push_char('€'); // 3 byte
data.push_char('𤭢'); // 4 byte
assert_eq!(~"ประเทศไทย中华b¢€𤭢", data);
}
#[test]
@ -3240,6 +3267,19 @@ mod tests {
"22".cmp(& &"1234") == Greater;
}
#[test]
fn test_char_range_at() {
let data = ~"b¢€𤭢𤭢€¢b";
assert_eq!('b', data.char_range_at(0).ch);
assert_eq!('¢', data.char_range_at(1).ch);
assert_eq!('€', data.char_range_at(3).ch);
assert_eq!('𤭢', data.char_range_at(6).ch);
assert_eq!('𤭢', data.char_range_at(10).ch);
assert_eq!('€', data.char_range_at(14).ch);
assert_eq!('¢', data.char_range_at(17).ch);
assert_eq!('b', data.char_range_at(19).ch);
}
#[test]
fn test_char_range_at_reverse_underflow() {
assert_eq!("abc".char_range_at_reverse(0).next, 0);

24
src/test/bench/core-std.rs
View File

@ -19,6 +19,7 @@ use std::os;
use std::rand::RngUtil;
use std::rand;
use std::result;
use std::str;
use std::uint;
use std::util;
use std::vec;
@ -36,6 +37,8 @@ fn main() {
bench!(vec_plus);
bench!(vec_append);
bench!(vec_push_all);
bench!(is_utf8_ascii);
bench!(is_utf8_multibyte);
}
fn maybe_run_test(argv: &[~str], name: ~str, test: &fn()) {
@ -127,3 +130,24 @@ fn vec_push_all() {
}
}
}
fn is_utf8_ascii() {
let mut v : ~[u8] = ~[];
for uint::range(0, 20000) |_| {
v.push('b' as u8);
if !str::is_utf8(v) {
fail!("is_utf8 failed");
}
}
}
fn is_utf8_multibyte() {
let s = "b¢€𤭢";
let mut v : ~[u8]= ~[];
for uint::range(0, 5000) |_| {
v.push_all(s.as_bytes());
if !str::is_utf8(v) {
fail!("is_utf8 failed");
}
}
}

11
src/test/run-pass/utf8_chars.rs
View File

@ -27,9 +27,20 @@ pub fn main() {
assert!(s.char_at(1u) == 'é');
assert!((str::is_utf8(s.as_bytes())));
// invalid prefix
assert!((!str::is_utf8(~[0x80_u8])));
// invalid 2 byte prefix
assert!((!str::is_utf8(~[0xc0_u8])));
assert!((!str::is_utf8(~[0xc0_u8, 0x10_u8])));
// invalid 3 byte prefix
assert!((!str::is_utf8(~[0xe0_u8])));
assert!((!str::is_utf8(~[0xe0_u8, 0x10_u8])));
assert!((!str::is_utf8(~[0xe0_u8, 0xff_u8, 0x10_u8])));
// invalid 4 byte prefix
assert!((!str::is_utf8(~[0xf0_u8])));
assert!((!str::is_utf8(~[0xf0_u8, 0x10_u8])));
assert!((!str::is_utf8(~[0xf0_u8, 0xff_u8, 0x10_u8])));
assert!((!str::is_utf8(~[0xf0_u8, 0xff_u8, 0xff_u8, 0x10_u8])));
let mut stack = ~"a×c€";
assert_eq!(stack.pop_char(), '€');