minor code cleanup; load balance bm_suffix

git-svn: trunk@3360

ChangeLog

@@ -1,3 +1,7 @@
+Tue Nov  6 17:17:56 CET 2007 (tk)
+---------------------------------
+  * libclamav/matcher-bm.c: minor code cleanup; load balance bm_suffix
+
 Tue Nov  6 16:13:08 GMT 2007 (njh)
 ----------------------------------
   * libclamav/vba_extract.c:	Removed more unused code

libclamav/matcher-bm.c

@@ -30,21 +30,13 @@
 #include "matcher-bm.h"
 #include "filetypes.h"
 
-/* TODO: Check prefix regularity and automatically transfer some signatures
- *	 to AC
- */
-
 #define BM_MIN_LENGTH	3
-/* #define BM_TEST_OFFSET	5 */
 #define BM_BLOCK_SIZE	3
-
 #define HASH(a,b,c) (211 * a + 37 * b + c)
 
-
 int cli_bm_addpatt(struct cli_matcher *root, struct cli_bm_patt *pattern)
 {
-	int i;
-	uint16_t idx;
+	uint16_t idx, i;
 	const unsigned char *pt = pattern->pattern;
 	struct cli_bm_patt *prev, *next = NULL;
 
@@ -54,16 +46,29 @@ int cli_bm_addpatt(struct cli_matcher *root, struct cli_bm_patt *pattern)
 	return CL_EPATSHORT;
     }
 
-    for(i = BM_MIN_LENGTH - BM_BLOCK_SIZE; i >= 0; i--) {
+#if BM_MIN_LENGTH == BM_BLOCK_SIZE
+    /* try to load balance bm_suffix (at the cost of bm_shift) */
+    for(i = 0; i < pattern->length - BM_BLOCK_SIZE + 1; i++) {
 	idx = HASH(pt[i], pt[i + 1], pt[i + 2]);
-	root->bm_shift[idx] = MIN(root->bm_shift[idx], BM_MIN_LENGTH - BM_BLOCK_SIZE - i);
+	if(!root->bm_suffix[idx]) {
+	    if(i) {
+		pattern->prefix = pattern->pattern;
+		pattern->prefix_length = i;
+		pattern->pattern = &pattern->pattern[i];
+		pattern->length -= i;
+		pt = pattern->pattern;
+	    }
+	    break;
+	}
     }
+#endif
 
-    i = BM_MIN_LENGTH - BM_BLOCK_SIZE;
-    idx = HASH(pt[i], pt[i + 1], pt[i + 2]);
+    for(i = 0; i <= BM_MIN_LENGTH - BM_BLOCK_SIZE; i++) {
+	idx = HASH(pt[i], pt[i + 1], pt[i + 2]);
+	root->bm_shift[idx] = MIN(root->bm_shift[idx], BM_MIN_LENGTH - BM_BLOCK_SIZE - i);
+    }
 
     prev = next = root->bm_suffix[idx];
-
     while(next) {
 	if(pt[0] >= next->pattern[0])
 	    break;
@@ -73,25 +78,24 @@ int cli_bm_addpatt(struct cli_matcher *root, struct cli_bm_patt *pattern)
 
     if(next == root->bm_suffix[idx]) {
 	pattern->next = root->bm_suffix[idx];
+	if(root->bm_suffix[idx])
+	    pattern->cnt = root->bm_suffix[idx]->cnt;
 	root->bm_suffix[idx] = pattern;
     } else {
 	pattern->next = prev->next;
 	prev->next = pattern;
     }
+    root->bm_suffix[idx]->cnt++;
 
-    return 0;
+    return CL_SUCCESS;
 }
 
 int cli_bm_init(struct cli_matcher *root)
 {
-	unsigned int i;
-	unsigned int size = HASH(256, 256, 256);
+	uint16_t i, size = HASH(255, 255, 255) + 1;
 
 
-    cli_dbgmsg("in cli_bm_init()\n");
-    cli_dbgmsg("BM: Number of indexes = %d\n", size);
-
-    if(!(root->bm_shift = (int *) cli_malloc(size * sizeof(int))))
+    if(!(root->bm_shift = (uint8_t *) cli_malloc(size * sizeof(uint8_t))))
 	return CL_EMEM;
 
     if(!(root->bm_suffix = (struct cli_bm_patt **) cli_calloc(size, sizeof(struct cli_bm_patt *)))) {
@@ -102,14 +106,13 @@ int cli_bm_init(struct cli_matcher *root)
     for(i = 0; i < size; i++)
 	root->bm_shift[i] = BM_MIN_LENGTH - BM_BLOCK_SIZE + 1;
 
-    return 0;
+    return CL_SUCCESS;
 }
 
 void cli_bm_free(struct cli_matcher *root)
 {
-	struct cli_bm_patt *b1, *b2;
-	unsigned int i;
-	unsigned int size = HASH(256, 256, 256);
+	struct cli_bm_patt *patt, *prev;
+	uint16_t i, size = HASH(255, 255, 255) + 1;
 
 
     if(root->bm_shift)
@@ -117,17 +120,19 @@ void cli_bm_free(struct cli_matcher *root)
 
     if(root->bm_suffix) {
 	for(i = 0; i < size; i++) {
-	    b1 = root->bm_suffix[i];
-	    while(b1) {
-		b2 = b1;
-		b1 = b1->next;
-		if(b2->virname)
-		    free(b2->virname);
-		if(b2->offset)
-		    free(b2->offset);
-		if(b2->pattern)
-		    free(b2->pattern);
-		free(b2);
+	    patt = root->bm_suffix[i];
+	    while(patt) {
+		prev = patt;
+		patt = patt->next;
+		if(prev->prefix)
+		    free(prev->prefix);
+		else
+		    free(prev->pattern);
+		if(prev->virname)
+		    free(prev->virname);
+		if(prev->offset)
+		    free(prev->offset);
+		free(prev);
 	    }
 	}
 	free(root->bm_suffix);
@@ -136,11 +141,11 @@ void cli_bm_free(struct cli_matcher *root)
 
 int cli_bm_scanbuff(const unsigned char *buffer, uint32_t length, const char **virname, const struct cli_matcher *root, uint32_t offset, cli_file_t ftype, int fd)
 {
-	unsigned int i, j, shift, off, found = 0;
-	int idxtest;
-	uint16_t idx;
+	uint32_t i, j, off;
+	uint8_t found, pchain, shift;
+	uint16_t idx, idxchk;
 	struct cli_bm_patt *p;
-	const unsigned char *bp;
+	const unsigned char *bp, *pt;
 	unsigned char prefix;
 	struct cli_target_info info;
 
@@ -155,49 +160,56 @@ int cli_bm_scanbuff(const unsigned char *buffer, uint32_t length, const char **v
 
     for(i = BM_MIN_LENGTH - BM_BLOCK_SIZE; i < length - BM_BLOCK_SIZE + 1; ) {
 	idx = HASH(buffer[i], buffer[i + 1], buffer[i + 2]);
-
 	shift = root->bm_shift[idx];
 
 	if(shift == 0) {
-
 	    prefix = buffer[i - BM_MIN_LENGTH + BM_BLOCK_SIZE];
 	    p = root->bm_suffix[idx];
+	    pchain = 0;
+	    while(p) {
+		if(p->pattern[0] != prefix) {
+		    if(pchain)
+			break;
+		    p = p->next;
+		    continue;
+		} else pchain = 1;
 
-	    while(p && p->pattern[0] != prefix)
-		p = p->next;
-
-	    while(p && p->pattern[0] == prefix) {
 		off = i - BM_MIN_LENGTH + BM_BLOCK_SIZE;
 		bp = buffer + off;
 
-#ifdef BM_TEST_OFFSET
-		if(bp[BM_TEST_OFFSET] != p->pattern[BM_TEST_OFFSET]) {
+		if((off + p->length > length) || (p->prefix_length > off)) {
 		    p = p->next;
 		    continue;
 		}
-#endif
 
-		idxtest = MIN (p->length, length - off ) - 1;
-		if(idxtest >= 0) {
-		    if(bp[idxtest] != p->pattern[idxtest]) {
+		idxchk = MIN(p->length, length - off) - 1;
+		if(idxchk) {
+		    if((bp[idxchk] != p->pattern[idxchk]) ||  (bp[idxchk / 2] != p->pattern[idxchk / 2])) {
 			p = p->next;
 			continue;
 		    }
 		}
 
+		if(p->prefix_length) {
+		    off -= p->prefix_length;
+		    bp -= p->prefix_length;
+		    pt = p->prefix;
+		} else {
+		    pt = p->pattern;
+		}
+
 		found = 1;
-		for(j = 0; j < p->length && off < length; j++, off++) {
-		    if(bp[j] != p->pattern[j]) {
+		for(j = 0; j < p->length + p->prefix_length && off < length; j++, off++) {
+		    if(bp[j] != pt[j]) {
 			found = 0;
 			break;
 		    }
 		}
 
-		if(found && p->length == j) {
+		if(found && p->length + p->prefix_length == j) {
 
 		    if(p->target || p->offset) {
-			off = offset + i - BM_MIN_LENGTH + BM_BLOCK_SIZE;
-
+			off = offset + i - p->prefix_length - BM_MIN_LENGTH + BM_BLOCK_SIZE;
 			if((fd == -1 && !ftype) || !cli_validatesig(ftype, p->offset, off, &info, fd, p->virname)) {
 			    p = p->next;
 			    continue;

libclamav/matcher-bm.h

@@ -24,11 +24,12 @@
 #include "cltypes.h"
 
 struct cli_bm_patt {
-    unsigned char *pattern;
-    uint32_t length;
+    unsigned char *pattern, *prefix;
+    uint16_t length, prefix_length;
     char *virname, *offset;
     uint8_t target;
     struct cli_bm_patt *next;
+    uint16_t cnt;
 };
 
 int cli_bm_addpatt(struct cli_matcher *root, struct cli_bm_patt *pattern);

libclamav/matcher.h

@@ -43,7 +43,7 @@ struct cli_matcher {
     uint8_t ac_only;
 
     /* Extended Boyer-Moore */
-    int32_t *bm_shift;
+    uint8_t *bm_shift;
     struct cli_bm_patt **bm_suffix;
     uint32_t *soff, soff_len; /* for PE section sigs */