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