* re.c (rb_memsearch): a little improvement.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@3434 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
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@ -1,3 +1,7 @@
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Mon Feb 3 16:32:52 2003 Nobuyoshi Nakada <nobu.nokada@softhome.net>
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* re.c (rb_memsearch): a little improvement.
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Mon Feb 3 13:18:05 2003 Yukihiro Matsumoto <matz@ruby-lang.org>
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Mon Feb 3 13:18:05 2003 Yukihiro Matsumoto <matz@ruby-lang.org>
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* re.c (rb_memsearch): algorithm body of String#index.
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* re.c (rb_memsearch): algorithm body of String#index.
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25
re.c
25
re.c
@ -103,46 +103,47 @@ rb_memsearch(x0, m, y0, n)
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{
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{
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unsigned char *x = x0, *y = y0;
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unsigned char *x = x0, *y = y0;
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unsigned char *s, *e;
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unsigned char *s, *e;
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long d, i;
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long i;
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int d;
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unsigned long hx, hy;
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unsigned long hx, hy;
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#define KR_REHASH(a, b, h) ((((h) - (a)*d) << 1) + (b))
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#define KR_REHASH(a, b, h) (((h) << 1) - ((a)<<d) + (b))
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s = y; e = s + n - m + 1;
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s = y; e = s + n - m + 1;
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/* Preprocessing */
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/* Preprocessing */
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/* computes d = 2^(m-1) with
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/* computes d = 2^(m-1) with
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the left-shift operator */
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the left-shift operator */
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for (d = i = 1; i < m; ++i)
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d = sizeof(hx) * CHAR_BIT - 1;
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d = (d<<1);
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if (d > m) d = m;
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if (ruby_ignorecase) {
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if (ruby_ignorecase) {
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/* Prepare hash value */
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/* Prepare hash value */
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for (hy = hx = i = 0; i < m; ++i) {
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for (hy = hx = i = 0; i < d; ++i) {
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hx = ((hx<<1) + casetable[x[i]]);
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hx = KR_REHASH(0, casetable[x[i]], hx);
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hy = ((hy<<1) + casetable[s[i]]);
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hy = KR_REHASH(0, casetable[s[i]], hy);
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}
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}
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/* Searching */
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/* Searching */
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while (s < e) {
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while (s < e) {
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if (hx == hy && rb_memcicmp(x, s, m) == 0) {
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if (hx == hy && rb_memcicmp(x, s, m) == 0) {
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return s-y;
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return s-y;
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}
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}
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hy = KR_REHASH(casetable[*s], casetable[*(s+m)], hy);
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hy = KR_REHASH(casetable[*s], casetable[*(s+d)], hy);
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s++;
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s++;
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}
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}
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}
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}
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else {
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else {
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/* Prepare hash value */
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/* Prepare hash value */
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for (hy = hx = i = 0; i < m; ++i) {
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for (hy = hx = i = 0; i < d; ++i) {
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hx = ((hx<<1) + x[i]);
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hx = KR_REHASH(0, x[i], hx);
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hy = ((hy<<1) + s[i]);
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hy = KR_REHASH(0, s[i], hy);
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}
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}
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/* Searching */
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/* Searching */
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while (s < e) {
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while (s < e) {
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if (hx == hy && memcmp(x, s, m) == 0) {
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if (hx == hy && memcmp(x, s, m) == 0) {
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return s-y;
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return s-y;
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}
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}
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hy = KR_REHASH(*s, *(s+m), hy);
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hy = KR_REHASH(*s, *(s+d), hy);
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s++;
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s++;
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}
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}
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}
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}
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