linux内核字符串查找

Boyer-Moore算法实现

转载于 2009-03-23 16:45:00 发布 · 604 阅读

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#linux内核 #struct #c

本文介绍了一种高效的字符串搜索算法——Boyer-Moore算法的实现细节。该算法通过预处理模式串生成坏字符跳转表和好后缀跳转表，在文本中进行模式匹配，能够快速跳过大量不匹配的字符，显著提高搜索效率。

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/linux/lib/ts_bm.c /include/linux/textsearch.h

static unsigned int bm_find(struct ts_config *conf, struct ts_state *state)
{
    struct ts_bm *bm = ts_config_priv(conf);
    unsigned int i, text_len, consumed = state->offset;
    const u8 *text;
    int shift = bm->patlen, bs;

    for (;;) {
        text_len = conf->get_next_block(consumed, &text, conf, state);

        if (unlikely(text_len == 0))
            break;

        while (shift < text_len) {
            DEBUGP("Searching in position %d (%c)/n",
                shift, text[shift]);
            for (i = 0; i < bm->patlen; i++)
                 if (text[shift-i] != bm->pattern[bm->patlen-1-i])
                     goto next;

            /* London calling... */
            DEBUGP("found!/n");
            return consumed += (shift-(bm->patlen-1));

next:            bs = bm->bad_shift[text[shift-i]];

            /* Now jumping to... */
            shift = max_t(int, shift-i+bs, shift+bm->good_shift[i]);
        }
        consumed += text_len;
    }

    return UINT_MAX;
}