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string.c (str_index_str_by_char): simplify using str_index_str()

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Instead of its own version of quick search, now we use str_index_str()
and adjust character position. This change makes searching 4 times
faster in some cases; ref #6143
This commit is contained in:
Yukihiro "Matz" Matsumoto
2024-01-11 12:20:51 +09:00
parent e42f3b36f9
commit f646228dbe
1 changed files with 9 additions and 48 deletions
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src/string.c
+9 -48
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@@ -387,61 +387,22 @@ char_backtrack(const char *ptr, const char *end)
return end - 1;
}
static mrb_int
str_index_str_by_char_search(mrb_state *mrb, const char *p, const char *pend, const char *s, const mrb_int slen, mrb_int off)
{
/* Based on Quick Search algorithm (Boyer-Moore-Horspool algorithm) */
ptrdiff_t qstable[1 << CHAR_BIT];
/* Preprocessing */
{
mrb_int i;
for (i = 0; i < 1 << CHAR_BIT; i++) {
qstable[i] = slen;
}
for (i = 0; i < slen; i++) {
qstable[(unsigned char)s[i]] = slen - (i + 1);
}
}
/* Searching */
while (p < pend && pend - p >= slen) {
if (memcmp(p, s, slen) == 0) {
return off;
}
const char *pivot = p + qstable[(unsigned char)p[slen - 1]];
if (pivot >= pend || pivot < p /* overflowed */) { return -1; }
do {
p += mrb_utf8len(p, pend);
off++;
} while (p < pivot);
}
return -1;
}
static mrb_int
str_index_str_by_char(mrb_state *mrb, mrb_value str, mrb_value sub, mrb_int pos)
{
const char *p = RSTRING_PTR(str);
const char *pend = p + RSTRING_LEN(str);
const char *s = RSTRING_PTR(sub);
const mrb_int slen = RSTRING_LEN(sub);
mrb_int off = pos;
const char *ptr = RSTRING_PTR(sub);
mrb_int len = RSTRING_LEN(sub);
for (; pos > 0; pos --) {
if (pend - p < 1) { return -1; }
p += mrb_utf8len(p, pend);
if (pos > 0) {
pos = chars2bytes(str, 0, pos);
}
if (slen < 1) { return off; }
pos = mrb_str_index(mrb, str, ptr, len, pos);
return str_index_str_by_char_search(mrb, p, pend, s, slen, off);
if (pos > 0) {
pos = bytes2chars(str, pos);
}
return pos;
}
#else