Add ziplist test for deleting next to last entries

src/ziplist.c

@@ -1034,6 +1034,22 @@ int randstring(char *target, unsigned int min, unsigned int max) {
     return len;
 }
 
+void verify(unsigned char *zl, zlentry *e) {
+    int i;
+    int len = ziplistLen(zl);
+    zlentry _e;
+
+    for (i = 0; i < len; i++) {
+        memset(&e[i], 0, sizeof(zlentry));
+        e[i] = zipEntry(ziplistIndex(zl, i));
+
+        memset(&_e, 0, sizeof(zlentry));
+        _e = zipEntry(ziplistIndex(zl, -len+i));
+
+        assert(memcmp(&e[i], &_e, sizeof(zlentry)) == 0);
+    }
+}
+
 int main(int argc, char **argv) {
     unsigned char *zl, *p;
     unsigned char *entry;
@@ -1315,6 +1331,43 @@ int main(int argc, char **argv) {
         printf("SUCCESS\n\n");
     }
 
+    printf("Regression test deleting next to last entries:\n");
+    {
+        char v[3][257];
+        zlentry e[3];
+        int i;
+
+        for (i = 0; i < (sizeof(v)/sizeof(v[0])); i++) {
+            memset(v[i], 'a' + i, sizeof(v[0]));
+        }
+
+        v[0][256] = '\0';
+        v[1][  1] = '\0';
+        v[2][256] = '\0';
+
+        zl = ziplistNew();
+        for (i = 0; i < (sizeof(v)/sizeof(v[0])); i++) {
+            zl = ziplistPush(zl, (unsigned char *) v[i], strlen(v[i]), ZIPLIST_TAIL);
+        }
+
+        verify(zl, e);
+
+        assert(e[0].prevrawlensize == 1);
+        assert(e[1].prevrawlensize == 5);
+        assert(e[2].prevrawlensize == 1);
+
+        /* Deleting entry 1 will increase `prevrawlensize` for entry 2 */
+        unsigned char *p = e[1].p;
+        zl = ziplistDelete(zl, &p);
+
+        verify(zl, e);
+
+        assert(e[0].prevrawlensize == 1);
+        assert(e[1].prevrawlensize == 5);
+
+        printf("SUCCESS\n\n");
+    }
+
     printf("Create long list and check indices:\n");
     {
         zl = ziplistNew();