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string: address performance concerns for strncmp()

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This commit is contained in:
Alex Lyon
2018-03-09 13:19:35 -08:00
parent 3890ec58f0
commit 50f79e9a0e
4 changed files with 25 additions and 16 deletions
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src/string/src/lib.rs
+7 -15
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@@ -156,25 +156,17 @@ pub unsafe extern "C" fn strncat(s1: *mut c_char, s2: *const c_char, n: usize) -
#[no_mangle]
pub unsafe extern "C" fn strncmp(s1: *const c_char, s2: *const c_char, n: usize) -> c_int {
let s1 = platform::c_str_n(s1, n);
let s2 = platform::c_str_n(s2, n);
let s1 = core::slice::from_raw_parts(s1 as *const c_uchar, n);
let s2 = core::slice::from_raw_parts(s2 as *const c_uchar, n);
let min_len = n.min(s1.len()).min(s2.len());
for i in 0..min_len {
let val = s1[i] - s2[i];
if val != 0 {
return val as c_int;
for (&a, &b) in s1.iter().zip(s2.iter()) {
let val = (a as c_int) - (b as c_int);
if val != 0 || a == 0 {
return val;
}
}
// we can't just check for the NUL byte in the loop as c_str_n() removes it
if s1.len() > s2.len() {
s1[min_len] as c_int
} else if s1.len() < s2.len() {
-(s2[min_len] as c_int)
} else {
0
}
0
}
#[no_mangle]