bxs*: fix overflows and add assertions

first = -1 overflows

source/algocfg.c

@@ -178,9 +178,9 @@ const struct algocfg ALGOCFGS[] = {
   [_BSDM6] = {_BSDM6, GOOD, ASAN, UNSATISFIABLE, 6, 0, 256, 256},
   [_BSDM7] = {_BSDM7, GOOD, ASAN, VFY_TIMEOUT, 7, 0, 256, 256},
   [_BSDM8] = {_BSDM8, GOOD, ASAN, UNSATISFIABLE, 8, 0, 256, 256},
-  [_BXS]  = {_BXS, FAIL, FAIL, VFY_TIMEOUT, 0, 0, 256, 256},
-  [_BXS1] = {_BXS1, GOOD, ASAN, VFY_PASS, 1, 0, 256, 256},
-  [_BXS2] = {_BXS2, GOOD, ASAN, VFY_PASS, 2, 0, 256, 256},
+  [_BXS]  = {_BXS, FAIL, FAIL, VFY_TIMEOUT, 2, 0, 256, 256},
+  [_BXS1] = {_BXS1, GOOD, ASAN, VFY_PASS, 0, 0, 256, 256},
+  [_BXS2] = {_BXS2, GOOD, ASAN, VFY_PASS, 3, 0, 256, 256},
   [_BXS3] = {_BXS3, GOOD, ASAN, VFY_PASS, 3, 0, 256, 256},
   [_BXS4] = {_BXS4, GOOD, ASAN, VFY_PASS, 4, 0, 256, 256},
   [_BXS6] = {_BXS6, GOOD, ASAN, VFY_PASS, 6, 0, 256, 256},

source/algorithms.h

@@ -405,9 +405,9 @@ const struct algo ALGOS[] = {
   [_BSDM6] = {_BSDM6, OK, "bsdm6", "Backward SNR DAWG Matching (m>=6)", 6, 0},
   [_BSDM7] = {_BSDM7, OK, "bsdm7", "Backward SNR DAWG Matching (m>=7)", 7, 0},
   [_BSDM8] = {_BSDM8, OK, "bsdm8", "Backward SNR DAWG Matching (m>=8)", 8, 0},
-  [_BXS] = {_BXS, FAIL, "bxs", "BNDMq with eXtended Shift", 0, 0}, // m>=2
-  [_BXS1] = {_BXS1, OK, "bxs1", "BXS with q-grams limit", 1, 0},
-  [_BXS2] = {_BXS2, OK, "bxs2", "BXS with q-grams limit", 2, 0},
+  [_BXS] = {_BXS, FAIL, "bxs", "BNDMq with eXtended Shift", 2, 0}, // m>=2
+  [_BXS1] = {_BXS1, OK, "bxs1", "BXS with q-grams limit", 0, 0},
+  [_BXS2] = {_BXS2, OK, "bxs2", "BXS with q-grams limit", 3, 0},
   [_BXS3] = {_BXS3, OK, "bxs3", "BXS with q-grams limit", 3, 0},
   [_BXS4] = {_BXS4, OK, "bxs4", "BXS with q-grams limit", 4, 0},
   [_BXS6] = {_BXS6, OK, "bxs6", "BXS with q-grams limit", 6, 0},

source/algos/bxs.c

@@ -26,6 +26,8 @@
  * Note: Original crashed with m=2: bin/asan/bxs aa 2 aa 2
  */
 
+#define MIN_M 2
+#include <assert.h>
 #include "include/define.h"
 #include "include/main.h"
 #include "include/search_small.h"
@@ -34,7 +36,7 @@
 int search(unsigned char *x, int m, unsigned char *y, int n) {
   unsigned int B[SIGMA] = {0}, D, set;
   int i, j, first, k, count;
-  if (m <= 2)
+  if (m <= Q)
     return search_small(x, m, y, n);
   int len = m;
   if (m > WORD)
@@ -57,11 +59,13 @@ int search(unsigned char *x, int m, unsigned char *y, int n) {
 
   BEGIN_SEARCHING
   /* Searching */
-  for (i = mq1; i < nq1; i += mq1) {
+  for (i = mq1 - 1; i <= nq1; i += mq1) {
+    assert(i >= 0);
+    assert(i <= n);
     D = B[y[i]];
     if (D) {
       j = i;
-      first = i - mq1;
+      first = i - mq1; // -1
       do {
         j--;
         if (D >= mask) {
@@ -73,9 +77,9 @@ int search(unsigned char *x, int m, unsigned char *y, int n) {
             if (k == 0)
               OUTPUT(first + 1);
           }
-          D = ((D << 1) | 1) & B[y[j]];
+          D = ((D << 1) | 1) & B[y[j + 1]];
         } else
-          D = (D << 1) & B[y[j]];
+          D = (D << 1) & B[y[j + 1]];
       } while (D && j > first);
     }
   }

source/algos/bxs1.c

@@ -22,7 +22,7 @@
  * International Symposium on Experimental Algorithms (SEA 2010)
  * Q is the dimension of q-grams
  *
- * Constraints: requires m>=1. inexact m>32
+ * Constraints: requires m>=1.
  */
 
 #include "include/define.h"
@@ -68,13 +68,13 @@ int search(unsigned char *x, int m, unsigned char *y, int n) {
       do {
         j--;
         if (D >= mask) {
-          if (j - first)
+          if (j > first)
             i = j;
           else {
-            for (k = m; y[first + k] == x[k - 1] && (k); k--)
+            for (k = m; k && (y[first + k] == x[k - 1]); k--)
               ;
             if (k == 0)
-              count++;
+              OUTPUT(first);
           }
           D = ((D << 1) | 1) & B[y[j]];
         } else

source/algos/bxs2.c

@@ -26,6 +26,7 @@
  * Note: Original crashed with m=2: bin/asan/bxs2 aa 2 aa 2
  */
 
+#define MIN_M 3
 #include "include/define.h"
 #include "include/main.h"
 #include "include/search_small.h"
@@ -69,7 +70,7 @@ int search(unsigned char *x, int m, unsigned char *y, int n) {
       do {
         j--;
         if (D >= mask) {
-          if (j - first)
+          if (j > first)
             i = j;
           else {
             //assert(first + len < n);

source/algos/bxs3.c

@@ -25,6 +25,7 @@
  * Constraints: requires m>=3. inexact m>32
  */
 
+#define MIN_M 3
 #include "include/define.h"
 #include "include/main.h"
 #include "include/search_small.h"
@@ -68,13 +69,13 @@ int search(unsigned char *x, int m, unsigned char *y, int n) {
       do {
         j--;
         if (D >= mask) {
-          if (j - first)
+          if (j > first)
             i = j;
           else {
-            for (k = m; y[first + k] == x[k - 1] && (k); k--)
+            for (k = m; k && (y[k + first] == x[k - 1]); k--)
               ;
             if (k == 0)
-              count++;
+              OUTPUT(first + 1);
           }
           D = ((D << 1) | 1) & B[y[j]];
         } else

source/algos/bxs4.c

@@ -25,6 +25,7 @@
  * Constraints: requires m>=4.
  */
 
+#define MIN_M 4
 #include "include/define.h"
 #include "include/main.h"
 #include "include/search_small.h"
@@ -70,7 +71,7 @@ int search(unsigned char *x, int m, unsigned char *y, int n) {
       do {
         j--;
         if (D >= mask) {
-          if (j - first)
+          if (j > first)
             i = j;
           else {
             for (k = len; k && (y[first + k] == x[k - 1]); k--)

source/algos/bxs6.c

@@ -25,6 +25,7 @@
  * Constraints: requires m>=6
  */
 
+#define MIN_M 6
 #include "include/define.h"
 #include "include/main.h"
 #include "include/search_small.h"
@@ -73,7 +74,7 @@ int search(unsigned char *x, int m, unsigned char *y, int n) {
       do {
         j--;
         if (D >= mask) {
-          if (j - first)
+          if (j > first)
             i = j;
           else {
             for (k = len; k && (y[first + k] == x[k - 1]); k--)

source/algos/bxs8.c

@@ -25,6 +25,8 @@
  * Constraints: requires m>=8
  */
 
+#define MIN_M 8
+#include <assert.h>
 #include "include/define.h"
 #include "include/main.h"
 #include "include/search_small.h"
@@ -75,7 +77,7 @@ int search(unsigned char *x, int m, unsigned char *y, int n) {
       do {
         j--;
         if (D >= mask) {
-          if (j - first)
+          if (j > first)
             i = j;
           else {
             for (k = len; k && (y[first + k] == x[k - 1]); k--)