Author: chromatic
Date: Thu Oct 4 10:57:04 2007
New Revision: 21844
Modified:
trunk/src/utils.c
Log:
[src] Further optimizations to Parrot_byte_index() thanks to feedback from Andy
Dougherty. Using memchr() instead of strchr() is a further gain. This code is
now about seven times faster than it was, per the regex tests as a benchmark.
Modified: trunk/src/utils.c
==============================================================================
--- trunk/src/utils.c (original)
+++ trunk/src/utils.c Thu Oct 4 10:57:04 2007
@@ -647,32 +647,29 @@
Parrot_byte_index(SHIM_INTERP, NOTNULL(const STRING *base),
NOTNULL(const STRING *search), UINTVAL start_offset)
{
- const INTVAL searchlen = search->strlen;
- const char * const search_start = search->strstart;
- const char * const base_start = base->strstart;
- const INTVAL max_offset = base->strlen - searchlen;
- const char * const max_pos = base_start + max_offset;
-
- /* looking for the first character of the search string can avoid having to
- * inch along, comparing everything. However, if the base string has
- * embedded nulls, strchr() will stop at the first one, so inching along is
- * the only good solution */
- char *start_pos = strchr(base_start + start_offset, *search_start);
-
- /* strchr() returns NULL for no match, so start at the start position */
- if (!start_pos)
- start_pos = base_start + start_offset;
-
- while (start_pos <= max_pos) {
- /* only do the memcmp() if the first character matches */
- if ( *start_pos == *search_start
- && memcmp(start_pos, search_start, searchlen) == 0)
-
- /* return the offset, not the pointer to the position */
- return start_pos - base_start;
+ const char * const str_start = base->strstart;
+ const INTVAL str_len = base->strlen;
+ const char * const search_str = search->strstart;
+ const INTVAL search_len = search->strlen;
+ char *str_pos = str_start + start_offset;
+ INTVAL len_remain = str_len - start_offset;
+ char *search_pos;
+
+ /* find the next position of the first character in the search string
+ * Parrot strings can have NULLs, so strchr() won't work here */
+ while ((search_pos = (char *)memchr(str_pos, *search_str, len_remain))) {
+ const INTVAL offset = search_pos - str_start;
+
+ /* now look for the entire string */
+ if (memcmp(search_pos, search_str, search_len) == 0)
+ return offset;
+
+ /* otherwise loop and memchr() with the rest of the string */
+ len_remain = str_len - offset;
+ str_pos = search_pos + 1;
- /* walking is necessary in case of embedded null bytes */
- start_pos++;
+ if (len_remain < search_len)
+ return -1;
}
return -1;
