mirror of
https://github.com/python/cpython.git
synced 2024-11-28 16:45:42 +01:00
7108bdf27c
Generally comparable perf for the "good" case where memchr doesn't return any collisions (false matches on lower byte) but clearly faster with collisions.
54 lines
1.8 KiB
C
54 lines
1.8 KiB
C
/* stringlib: replace implementation */
|
|
|
|
#ifndef STRINGLIB_FASTSEARCH_H
|
|
#error must include "stringlib/fastsearch.h" before including this module
|
|
#endif
|
|
|
|
Py_LOCAL_INLINE(void)
|
|
STRINGLIB(replace_1char_inplace)(STRINGLIB_CHAR* s, STRINGLIB_CHAR* end,
|
|
Py_UCS4 u1, Py_UCS4 u2, Py_ssize_t maxcount)
|
|
{
|
|
*s = u2;
|
|
while (--maxcount && ++s != end) {
|
|
/* Find the next character to be replaced.
|
|
|
|
If it occurs often, it is faster to scan for it using an inline
|
|
loop. If it occurs seldom, it is faster to scan for it using a
|
|
function call; the overhead of the function call is amortized
|
|
across the many characters that call covers. We start with an
|
|
inline loop and use a heuristic to determine whether to fall back
|
|
to a function call. */
|
|
if (*s != u1) {
|
|
int attempts = 10;
|
|
/* search u1 in a dummy loop */
|
|
while (1) {
|
|
if (++s == end)
|
|
return;
|
|
if (*s == u1)
|
|
break;
|
|
if (!--attempts) {
|
|
/* if u1 was not found for attempts iterations,
|
|
use FASTSEARCH() or memchr() */
|
|
#ifdef STRINGLIB_FAST_MEMCHR
|
|
s++;
|
|
s = STRINGLIB_FAST_MEMCHR(s, u1, end - s);
|
|
if (s == NULL)
|
|
return;
|
|
#else
|
|
Py_ssize_t i;
|
|
STRINGLIB_CHAR ch1 = (STRINGLIB_CHAR) u1;
|
|
s++;
|
|
i = FASTSEARCH(s, end - s, &ch1, 1, 0, FAST_SEARCH);
|
|
if (i < 0)
|
|
return;
|
|
s += i;
|
|
#endif
|
|
/* restart the dummy loop */
|
|
break;
|
|
}
|
|
}
|
|
}
|
|
*s = u2;
|
|
}
|
|
}
|