Fix hash table deletion to prevent lost entries

Use negative used value to mark deleted entry.  Search keeps probing
past deleted entries.  Adding an entry uses first deleted entry when
it hits end of probe chain.

Initially found that "ramdiskimage" and "preboot" collide modulus 347,
causing "preboot" to be inserted at idx 190, "ramdiskimage" at idx 191.
Previous to this fix when "preboot" is deleted, "ramdiskimage" is
orphaned.

Signed-off-by: Peter Barada <peter.barada@logicpd.com>
Tested-by: Wolfgang Denk <wd@denx.de>

lib/hashtable.c

@@ -65,7 +65,7 @@
  * which describes the current status.
  */
 typedef struct _ENTRY {
-	unsigned int used;
+	int used;
 	ENTRY entry;
 } _ENTRY;
 
@@ -152,7 +152,7 @@ void hdestroy_r(struct hsearch_data *htab)
 
 	/* free used memory */
 	for (i = 1; i <= htab->size; ++i) {
-		if (htab->table[i].used) {
+		if (htab->table[i].used > 0) {
 			ENTRY *ep = &htab->table[i].entry;
 
 			free(ep->key);
@@ -209,7 +209,7 @@ int hmatch_r(const char *match, int last_idx, ENTRY ** retval,
 	size_t key_len = strlen(match);
 
 	for (idx = last_idx + 1; idx < htab->size; ++idx) {
-		if (!htab->table[idx].used)
+		if (htab->table[idx].used > 0)
 			continue;
 		if (!strncmp(match, htab->table[idx].entry.key, key_len)) {
 			*retval = &htab->table[idx].entry;
@@ -229,6 +229,7 @@ int hsearch_r(ENTRY item, ACTION action, ENTRY ** retval,
 	unsigned int count;
 	unsigned int len = strlen(item.key);
 	unsigned int idx;
+	unsigned int first_deleted = 0;
 
 	/* Compute an value for the given string. Perhaps use a better method. */
 	hval = len;
@@ -256,6 +257,10 @@ int hsearch_r(ENTRY item, ACTION action, ENTRY ** retval,
 		 */
 		unsigned hval2;
 
+		if (htab->table[idx].used == -1
+		    && !first_deleted)
+			first_deleted = idx;
+
 		if (htab->table[idx].used == hval
 		    && strcmp(item.key, htab->table[idx].entry.key) == 0) {
 			/* Overwrite existing value? */
@@ -335,6 +340,9 @@ int hsearch_r(ENTRY item, ACTION action, ENTRY ** retval,
 		 * Create new entry;
 		 * create copies of item.key and item.data
 		 */
+		if (first_deleted)
+			idx = first_deleted;
+
 		htab->table[idx].used = hval;
 		htab->table[idx].entry.key = strdup(item.key);
 		htab->table[idx].entry.data = strdup(item.data);
@@ -387,7 +395,7 @@ int hdelete_r(const char *key, struct hsearch_data *htab)
 
 	free(ep->key);
 	free(ep->data);
-	htab->table[idx].used = 0;
+	htab->table[idx].used = -1;
 
 	--htab->filled;
 
@@ -467,7 +475,7 @@ ssize_t hexport_r(struct hsearch_data *htab, const char sep,
 	 */
 	for (i = 1, n = 0, totlen = 0; i <= htab->size; ++i) {
 
-		if (htab->table[i].used) {
+		if (htab->table[i].used > 0) {
 			ENTRY *ep = &htab->table[i].entry;
 
 			list[n++] = ep;