cosmopolitan/third_party/python/Objects/stringlib/replace.inc
Justine Tunney d26d7ae0e4 Perform build and magnum tuning
Building o//third_party/python now takes 5 seconds on my PC

This change works towards modifying Python to use runtime dispatching
when appropriate. For example, when loading the magnums in the socket
module, it's a good idea to check if the magnum is zero, because that
means the local system platform doesn't support it.
2021-08-10 10:26:13 -07:00

54 lines
1.8 KiB
C++

/* clang-format off */
/* stringlib: replace implementation */
#ifndef STRINGLIB_FASTSEARCH_H
#error must include fastsearch.inc 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() */
#if STRINGLIB_SIZEOF_CHAR == 1
s++;
s = 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;
}
}