Fix quadratic performance issue in list numbering.

Author: kevinbackhouse

src/commonmark.c

@@ -231,19 +231,15 @@ static int S_render_node(cmark_renderer *renderer, cmark_node *node,
       LIT("<!-- end list -->");
       BLANKLINE();
     }
+    renderer->list_number = cmark_node_get_list_start(node);
     break;
 
   case CMARK_NODE_ITEM:
     if (cmark_node_get_list_type(node->parent) == CMARK_BULLET_LIST) {
       marker_width = 4;
     } else {
-      list_number = cmark_node_get_list_start(node->parent);
+      list_number = renderer->list_number++;
       list_delim = cmark_node_get_list_delim(node->parent);
-      tmp = node;
-      while (tmp->prev) {
-        tmp = tmp->prev;
-        list_number += 1;
-      }
       // we ensure a width of at least 4 so
       // we get nice transition from single digits
       // to double

src/man.c

@@ -114,6 +114,7 @@ static int S_render_node(cmark_renderer *renderer, cmark_node *node,
     break;
 
   case CMARK_NODE_LIST:
+    renderer->list_number = cmark_node_get_list_start(node);
     break;
 
   case CMARK_NODE_ITEM:
@@ -123,12 +124,7 @@ static int S_render_node(cmark_renderer *renderer, cmark_node *node,
       if (cmark_node_get_list_type(node->parent) == CMARK_BULLET_LIST) {
         LIT("\\[bu] 2");
       } else {
-        list_number = cmark_node_get_list_start(node->parent);
-        tmp = node;
-        while (tmp->prev) {
-          tmp = tmp->prev;
-          list_number += 1;
-        }
+        list_number = renderer->list_number++;
         char list_number_s[LIST_NUMBER_SIZE];
         snprintf(list_number_s, LIST_NUMBER_SIZE, "\"%d.\" 4", list_number);
         LIT(list_number_s);

src/plaintext.c

@@ -76,19 +76,15 @@ static int S_render_node(cmark_renderer *renderer, cmark_node *node,
                                     node->next->type == CMARK_NODE_LIST)) {
       CR();
     }
+    renderer->list_number = cmark_node_get_list_start(node);
     break;
 
   case CMARK_NODE_ITEM:
     if (cmark_node_get_list_type(node->parent) == CMARK_BULLET_LIST) {
       marker_width = 4;
     } else {
-      list_number = cmark_node_get_list_start(node->parent);
+      list_number = renderer->list_number++;
       list_delim = cmark_node_get_list_delim(node->parent);
-      tmp = node;
-      while (tmp->prev) {
-        tmp = tmp->prev;
-        list_number += 1;
-      }
       // we ensure a width of at least 4 so
       // we get nice transition from single digits
       // to double

src/render.c

@@ -177,8 +177,8 @@ char *cmark_render(cmark_mem *mem, cmark_node *root, int options, int width,
 
   cmark_renderer renderer = {mem,   &buf, &pref, 0,           width,
                              0,     0,    true,  true,        false,
-                             false, outc, S_cr,  S_blankline, S_out,
-                             0};
+                             false, 0,    outc,  S_cr,        S_blankline,
+                             S_out, 0};
 
   while ((ev_type = cmark_iter_next(iter)) != CMARK_EVENT_DONE) {
     cur = cmark_iter_get_node(iter);

src/render.h

@@ -23,6 +23,7 @@ struct cmark_renderer {
   bool begin_content;
   bool no_linebreaks;
   bool in_tight_list_item;
+  int list_number;
   void (*outc)(struct cmark_renderer *, cmark_node *, cmark_escaping, int32_t, unsigned char);
   void (*cr)(struct cmark_renderer *);
   void (*blankline)(struct cmark_renderer *);