Issue #7462: Implement the stringlib fast search algorithm for the `rfind`,
`rindex`, `rsplit` and `rpartition` methods. Patch by Florent Xicluna.
diff --git a/Objects/stringlib/fastsearch.h b/Objects/stringlib/fastsearch.h
index 23bccfb..7b9dd47 100644
--- a/Objects/stringlib/fastsearch.h
+++ b/Objects/stringlib/fastsearch.h
@@ -5,7 +5,7 @@
/* fast search/count implementation, based on a mix between boyer-
moore and horspool, with a few more bells and whistles on the top.
- for some more background, see: http://effbot.org/stringlib.htm */
+ for some more background, see: http://effbot.org/zone/stringlib.htm */
/* note: fastsearch may access s[n], which isn't a problem when using
Python's ordinary string types, but may cause problems if you're
@@ -16,6 +16,7 @@
#define FAST_COUNT 0
#define FAST_SEARCH 1
+#define FAST_RSEARCH 2
Py_LOCAL_INLINE(Py_ssize_t)
fastsearch(const STRINGLIB_CHAR* s, Py_ssize_t n,
@@ -41,51 +42,92 @@
if (s[i] == p[0])
count++;
return count;
- } else {
+ } 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;
}
mlast = m - 1;
-
- /* create compressed boyer-moore delta 1 table */
skip = mlast - 1;
- /* process pattern[:-1] */
- for (mask = i = 0; i < mlast; i++) {
- mask |= (1 << (p[i] & 0x1F));
- if (p[i] == p[mlast])
- skip = mlast - i - 1;
- }
- /* process pattern[-1] outside the loop */
- mask |= (1 << (p[mlast] & 0x1F));
- for (i = 0; i <= w; i++) {
- /* note: using mlast in the skip path slows things down on x86 */
- if (s[i+m-1] == p[m-1]) {
- /* candidate match */
- for (j = 0; j < mlast; j++)
- if (s[i+j] != p[j])
- break;
- if (j == mlast) {
- /* got a match! */
- if (mode != FAST_COUNT)
- return i;
- count++;
- i = i + mlast;
- continue;
+ if (mode != FAST_RSEARCH) {
+
+ /* create compressed boyer-moore delta 1 table */
+
+ /* process pattern[:-1] */
+ for (mask = i = 0; i < mlast; i++) {
+ mask |= (1 << (p[i] & 0x1F));
+ if (p[i] == p[mlast])
+ skip = mlast - i - 1;
+ }
+ /* process pattern[-1] outside the loop */
+ mask |= (1 << (p[mlast] & 0x1F));
+
+ for (i = 0; i <= w; i++) {
+ /* note: using mlast in the skip path slows things down on x86 */
+ if (s[i+m-1] == p[m-1]) {
+ /* candidate match */
+ for (j = 0; j < mlast; j++)
+ if (s[i+j] != p[j])
+ break;
+ if (j == mlast) {
+ /* got a match! */
+ if (mode != FAST_COUNT)
+ return i;
+ count++;
+ i = i + mlast;
+ continue;
+ }
+ /* miss: check if next character is part of pattern */
+ if (!(mask & (1 << (s[i+m] & 0x1F))))
+ i = i + m;
+ else
+ i = i + skip;
+ } else {
+ /* skip: check if next character is part of pattern */
+ if (!(mask & (1 << (s[i+m] & 0x1F))))
+ i = i + m;
}
- /* miss: check if next character is part of pattern */
- if (!(mask & (1 << (s[i+m] & 0x1F))))
- i = i + m;
- else
- i = i + skip;
- } else {
- /* skip: check if next character is part of pattern */
- if (!(mask & (1 << (s[i+m] & 0x1F))))
- i = i + m;
+ }
+ } else { /* FAST_RSEARCH */
+
+ /* create compressed boyer-moore delta 1 table */
+
+ /* process pattern[0] outside the loop */
+ mask = (1 << (p[0] & 0x1F));
+ /* process pattern[:0:-1] */
+ for (i = mlast; i > 0; i--) {
+ mask |= (1 << (p[i] & 0x1F));
+ if (p[i] == p[0])
+ skip = i - 1;
+ }
+
+ for (i = w; i >= 0; i--) {
+ if (s[i] == p[0]) {
+ /* candidate match */
+ for (j = mlast; j > 0; j--)
+ if (s[i+j] != p[j])
+ break;
+ if (j == 0)
+ /* got a match! */
+ return i;
+ /* miss: check if previous character is part of pattern */
+ if (!(mask & (1 << (s[i-1] & 0x1F))))
+ i = i - m;
+ else
+ i = i - skip;
+ } else {
+ /* skip: check if previous character is part of pattern */
+ if (!(mask & (1 << (s[i-1] & 0x1F))))
+ i = i - m;
+ }
}
}