Avoid unnecessary (and potentially dangerous) memmove

[mnemon] / mnemon.c

diff --git a/mnemon.c b/mnemon.c
index e13d3b9ff9f707f458a8ca02ec5b0c31818922a9..25ba65fac17040f6b6600c6defa9d0bebcf1638f 100644 (file)
--- a/mnemon.c
+++ b/mnemon.c
@@ -366,12 +366,14 @@ mnemon_get_bin (mnemon_t  *mnemon,
        else if (mnemon->bins[i].count > count)
            break;
 
-    mnemon_bins_grow (mnemon);
+    if (mnemon->num_bins == mnemon->bins_size)
+       mnemon_bins_grow (mnemon);
 
     bin = &mnemon->bins[i];
 
     /* Make room to insert new bin at its sorted location. */
-    memmove (bin + 1, bin, (mnemon->num_bins - i) * sizeof (bin_t));
+    if (i < mnemon->num_bins)
+       memmove (bin + 1, bin, (mnemon->num_bins - i) * sizeof (bin_t));
     mnemon->num_bins++;
 
     bin_init (bin, count);
@@ -385,6 +387,8 @@ mnemon_remove_bin (mnemon_t *mnemon,
 {
     int i = bin - mnemon->bins;
 
+    bin_fini (bin);
+
     memmove (bin, bin + 1, (mnemon->num_bins - i) * sizeof (bin_t));
     mnemon->num_bins--;
 }
@@ -543,7 +547,7 @@ mnemon_save (mnemon_t *mnemon)
 
        err = rename (lock_filename, filename);
        if (err < 0) {
-           fprintf (stderr, "Error: Failes to rename %s to %s: %s\n",
+           fprintf (stderr, "Error: Failed to rename %s to %s: %s\n",
                     lock_filename, filename, strerror (errno));
            continue;
        }
@@ -622,16 +626,46 @@ mnemon_select_item (mnemon_t       *mnemon,
 }
 
 static void
-mnemon_do_challenges (mnemon_t *mnemon)
+mnemon_do_challenges (mnemon_t *mnemon,
+                     int       to_introduce)
 {
     bin_t *bin;
     int item_index;
     item_t *item;
     char *response;
     bool_t correct;
+    int unlearned;
+    int i;
 
-    while (1) {
+    /* Count the number of items with negative counts. */
+    unlearned = 0;
+    for (i = 0; i < mnemon->num_bins; i++) {
+       bin = &mnemon->bins[i];
+       if (bin->count >= 0)
+           break;
+       unlearned += bin->num_items;
+    }
+
+    to_introduce -= unlearned;
+    if (to_introduce < 0)
+       to_introduce = 0;
+
+    if (unlearned) {
+       printf ("You've got %d items to learn already. ", unlearned);
+       if (to_introduce)
+           printf ("I'll introduce %d more as we go.", to_introduce);
+       printf ("\n");
+    } else {
+       printf ("Introducing %d new items.\n", to_introduce);
+    }
+    printf ("\n");
+
+    do {
        mnemon_select_item (mnemon, &bin, &item_index);
+
+       if (bin->count == 0)
+           to_introduce--;
+
        item = bin->items[item_index];
 
        printf ("%s\n", item->challenge);
@@ -645,24 +679,61 @@ mnemon_do_challenges (mnemon_t *mnemon)
        correct = (strcmp (response, item->response) == 0);
 
        bin_remove_item (bin, item_index);
-       if (bin->num_items == 0)
+
+       /* If the bin is now empty, we must remove it. Also if we just
+        * picked the last word we'll ever pick from the bin with
+        * count 0, then we can remove that as well. */
+       if (bin->num_items == 0 ||
+           (bin->count == 0 && to_introduce == 0))
+       {
            mnemon_remove_bin (mnemon, bin);
+       }
 
        if (correct) {
-           printf ("Correct!\n\n");
            item->count++;
+           /* We reserve an item count of 0 for an item that has
+            * never been asked. */
+           if (item->count == 0) {
+               item->count = 1;
+               unlearned--;
+               printf ("You got it!");
+           } else if (item->count < 0) {
+               printf ("Yes---just give me %d more.",
+                       - item->count);
+           } else if (item->count == 1) {
+               printf ("On your first try, no less!");
+           } else {
+               printf ("Masterful.");
+           }
        } else {
-           printf ("  %s is the correct answer.\n\n",
+           printf ("  %s is the correct answer.",
                    item->response);
+           if (item->count >= 0)
+               unlearned++;
            item->count--;
-           if (item->count > 0)
+           /* Penalize an incorrect response by forcing the count
+            * negative. */
+           if (item->count >= 0) {
                item->count = -1;
+               printf ( " Oops, you knew that, right?\n ");
+           }
        }
 
+       printf (" (");
+       if (to_introduce)
+           printf ("%d to come.", to_introduce);
+       if (to_introduce && unlearned)
+           printf (" ");
+       if (unlearned)
+           printf ("%d still unlearned.", unlearned);
+       if (to_introduce == 0 && unlearned == 0)
+           printf ("Great job!");
+       printf (")\n\n");
+
        bin = mnemon_get_bin (mnemon, item->count);
 
        bin_add_item (bin, item);
-    }
+    } while (unlearned || to_introduce);
 }
 
 int
@@ -670,13 +741,13 @@ main (int argc, char *argv[])
 {
     mnemon_t mnemon;
 
-    srand (1);
+    srand (time (NULL));
 
     mnemon_init (&mnemon);
 
     mnemon_load (&mnemon);
 
-    mnemon_do_challenges (&mnemon);
+    mnemon_do_challenges (&mnemon, 10);
 
     mnemon_save (&mnemon);