Issue #24821: Refactor STRINGLIB(fastsearch_memchr_1char) and split it on
STRINGLIB(find_char) and STRINGLIB(rfind_char) that can be used independedly
without special preconditions.
diff --git a/Objects/stringlib/fastsearch.h b/Objects/stringlib/fastsearch.h
index cda68e7..98165ad 100644
--- a/Objects/stringlib/fastsearch.h
+++ b/Objects/stringlib/fastsearch.h
@@ -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 @@
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 @@
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;
}