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Issue #24821: Refactor STRINGLIB(fastsearch_memchr_1char) and split it on

Browse source 
STRINGLIB(find_char) and STRINGLIB(rfind_char) that can be used independedly
without special preconditions.
This commit is contained in:
Serhiy Storchaka 2015-11-14 15:42:17 +02:00
parent 0304729ec4
commit 413fdcea21
4 changed files with 124 additions and 103 deletions
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156
Objects/stringlib/fastsearch.h
View file

@ -32,52 +32,98 @@
#define STRINGLIB_BLOOM(mask, ch) \
((mask & (1UL << ((ch) & (STRINGLIB_BLOOM_WIDTH -1)))))
Py_LOCAL_INLINE(Py_ssize_t)
STRINGLIB(find_char)(const STRINGLIB_CHAR* s, Py_ssize_t n, STRINGLIB_CHAR ch)
{
const STRINGLIB_CHAR *p, *e;
p = s;
e = s + n;
if (n > 10) {
#if STRINGLIB_SIZEOF_CHAR == 1
p = memchr(s, ch, n);
if (p != NULL)
return (p - s);
return -1;
#else
/* use memchr if we can choose a needle without two many likely
false positives */
unsigned char needle = ch & 0xff;
/* If looking for a multiple of 256, we'd have too
many false positives looking for the '\0' byte in UCS2
and UCS4 representations. */
if (needle != 0) {
while (p < e) {
void *candidate = memchr(p, needle,
(e - p) * sizeof(STRINGLIB_CHAR));
if (candidate == NULL)
return -1;
p = (const STRINGLIB_CHAR *)
_Py_ALIGN_DOWN(candidate, sizeof(STRINGLIB_CHAR));
if (*p == ch)
return (p - s);
/* False positive */
p++;
}
return -1;
}
#endif
}
while (p < e) {
if (*p == ch)
return (p - s);
p++;
}
return -1;
}
Py_LOCAL_INLINE(Py_ssize_t)
STRINGLIB(fastsearch_memchr_1char)(const STRINGLIB_CHAR* s, Py_ssize_t n,
STRINGLIB_CHAR ch, unsigned char needle,
int mode)
STRINGLIB(rfind_char)(const STRINGLIB_CHAR* s, Py_ssize_t n, STRINGLIB_CHAR ch)
{
if (mode == FAST_SEARCH) {
const STRINGLIB_CHAR *ptr = s;
const STRINGLIB_CHAR *e = s + n;
while (ptr < e) {
void *candidate = memchr((const void *) ptr, needle, (e - ptr) * sizeof(STRINGLIB_CHAR));
if (candidate == NULL)
return -1;
ptr = (const STRINGLIB_CHAR *) _Py_ALIGN_DOWN(candidate, sizeof(STRINGLIB_CHAR));
if (sizeof(STRINGLIB_CHAR) == 1 || *ptr == ch)
return (ptr - s);
/* False positive */
ptr++;
}
return -1;
}
const STRINGLIB_CHAR *p;
#ifdef HAVE_MEMRCHR
/* memrchr() is a GNU extension, available since glibc 2.1.91.
it doesn't seem as optimized as memchr(), but is still quite
faster than our hand-written loop in FASTSEARCH below */
else if (mode == FAST_RSEARCH) {
while (n > 0) {
const STRINGLIB_CHAR *found;
void *candidate = memrchr((const void *) s, needle, n * sizeof(STRINGLIB_CHAR));
if (candidate == NULL)
return -1;
found = (const STRINGLIB_CHAR *) _Py_ALIGN_DOWN(candidate, sizeof(STRINGLIB_CHAR));
n = found - s;
if (sizeof(STRINGLIB_CHAR) == 1 || *found == ch)
return n;
/* False positive */
}
return -1;
}
#endif
else {
assert(0); /* Should never get here */
return 0;
}
faster than our hand-written loop below */
#undef DO_MEMCHR
if (n > 10) {
#if STRINGLIB_SIZEOF_CHAR == 1
p = memrchr(s, ch, n);
if (p != NULL)
return (p - s);
return -1;
#else
/* use memrchr if we can choose a needle without two many likely
false positives */
unsigned char needle = ch & 0xff;
/* If looking for a multiple of 256, we'd have too
many false positives looking for the '\0' byte in UCS2
and UCS4 representations. */
if (needle != 0) {
while (n > 0) {
void *candidate = memrchr(s, needle,
n * sizeof(STRINGLIB_CHAR));
if (candidate == NULL)
return -1;
p = (const STRINGLIB_CHAR *)
_Py_ALIGN_DOWN(candidate, sizeof(STRINGLIB_CHAR));
n = p - s;
if (*p == ch)
return n;
/* False positive */
}
return -1;
}
#endif
}
#endif /* HAVE_MEMRCHR */
p = s + n;
while (p > s) {
p--;
if (*p == ch)
return (p - s);
}
return -1;
}
Py_LOCAL_INLINE(Py_ssize_t)
@ -99,25 +145,11 @@ FASTSEARCH(const STRINGLIB_CHAR* s, Py_ssize_t n,
if (m <= 0)
return -1;
/* use special case for 1-character strings */
if (n > 10 && (mode == FAST_SEARCH
#ifdef HAVE_MEMRCHR
|| mode == FAST_RSEARCH
#endif
)) {
/* use memchr if we can choose a needle without two many likely
false positives */
unsigned char needle;
needle = p[0] & 0xff;
#if STRINGLIB_SIZEOF_CHAR > 1
/* If looking for a multiple of 256, we'd have too
many false positives looking for the '\0' byte in UCS2
and UCS4 representations. */
if (needle != 0)
#endif
return STRINGLIB(fastsearch_memchr_1char)
(s, n, p[0], needle, mode);
}
if (mode == FAST_COUNT) {
if (mode == FAST_SEARCH)
return STRINGLIB(find_char)(s, n, p[0]);
else if (mode == FAST_RSEARCH)
return STRINGLIB(rfind_char)(s, n, p[0]);
else { /* FAST_COUNT */
for (i = 0; i < n; i++)
if (s[i] == p[0]) {
count++;
@ -125,14 +157,6 @@ FASTSEARCH(const STRINGLIB_CHAR* s, Py_ssize_t n,
return maxcount;
}
return count;
} else if (mode == FAST_SEARCH) {
for (i = 0; i < n; i++)
if (s[i] == p[0])
return i;
} else { /* FAST_RSEARCH */
for (i = n - 1; i > -1; i--)
if (s[i] == p[0])
return i;
}
return -1;
}