textsearch: ts_kmp: support case insensitive searching in Knuth-Morris-Pratt algorithm
Joonwoo Park [Tue, 8 Jul 2008 09:38:09 +0000 (02:38 -0700)]
Add support for case insensitive search to Knuth-Morris-Pratt algorithm.

Signed-off-by: Joonwoo Park <joonwpark81@gmail.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

lib/ts_kmp.c

index 3ced628..632f783 100644 (file)
@@ -33,6 +33,7 @@
 #include <linux/module.h>
 #include <linux/types.h>
 #include <linux/string.h>
+#include <linux/ctype.h>
 #include <linux/textsearch.h>
 
 struct ts_kmp
@@ -47,6 +48,7 @@ static unsigned int kmp_find(struct ts_config *conf, struct ts_state *state)
        struct ts_kmp *kmp = ts_config_priv(conf);
        unsigned int i, q = 0, text_len, consumed = state->offset;
        const u8 *text;
+       const int icase = conf->flags & TS_IGNORECASE;
 
        for (;;) {
                text_len = conf->get_next_block(consumed, &text, conf, state);
@@ -55,9 +57,11 @@ static unsigned int kmp_find(struct ts_config *conf, struct ts_state *state)
                        break;
 
                for (i = 0; i < text_len; i++) {
-                       while (q > 0 && kmp->pattern[q] != text[i])
+                       while (q > 0 && kmp->pattern[q]
+                           != (icase ? toupper(text[i]) : text[i]))
                                q = kmp->prefix_tbl[q - 1];
-                       if (kmp->pattern[q] == text[i])
+                       if (kmp->pattern[q]
+                           == (icase ? toupper(text[i]) : text[i]))
                                q++;
                        if (unlikely(q == kmp->pattern_len)) {
                                state->offset = consumed + i + 1;
@@ -72,24 +76,28 @@ static unsigned int kmp_find(struct ts_config *conf, struct ts_state *state)
 }
 
 static inline void compute_prefix_tbl(const u8 *pattern, unsigned int len,
-                                     unsigned int *prefix_tbl)
+                                     unsigned int *prefix_tbl, int flags)
 {
        unsigned int k, q;
+       const u8 icase = flags & TS_IGNORECASE;
 
        for (k = 0, q = 1; q < len; q++) {
-               while (k > 0 && pattern[k] != pattern[q])
+               while (k > 0 && (icase ? toupper(pattern[k]) : pattern[k])
+                   != (icase ? toupper(pattern[q]) : pattern[q]))
                        k = prefix_tbl[k-1];
-               if (pattern[k] == pattern[q])
+               if ((icase ? toupper(pattern[k]) : pattern[k])
+                   == (icase ? toupper(pattern[q]) : pattern[q]))
                        k++;
                prefix_tbl[q] = k;
        }
 }
 
 static struct ts_config *kmp_init(const void *pattern, unsigned int len,
-                                 gfp_t gfp_mask)
+                                 gfp_t gfp_mask, int flags)
 {
        struct ts_config *conf;
        struct ts_kmp *kmp;
+       int i;
        unsigned int prefix_tbl_len = len * sizeof(unsigned int);
        size_t priv_size = sizeof(*kmp) + len + prefix_tbl_len;
 
@@ -97,11 +105,16 @@ static struct ts_config *kmp_init(const void *pattern, unsigned int len,
        if (IS_ERR(conf))
                return conf;
 
+       conf->flags = flags;
        kmp = ts_config_priv(conf);
        kmp->pattern_len = len;
-       compute_prefix_tbl(pattern, len, kmp->prefix_tbl);
+       compute_prefix_tbl(pattern, len, kmp->prefix_tbl, flags);
        kmp->pattern = (u8 *) kmp->prefix_tbl + prefix_tbl_len;
-       memcpy(kmp->pattern, pattern, len);
+       if (flags & TS_IGNORECASE)
+               for (i = 0; i < len; i++)
+                       kmp->pattern[i] = toupper(((u8 *)pattern)[i]);
+       else
+               memcpy(kmp->pattern, pattern, len);
 
        return conf;
 }