From d6a1699e37257c0b3d4651a481ce0bf597bc4e45 Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Wed, 16 Nov 1994 16:09:11 -0200
Subject: [PATCH] uses a single list to keep allocated strings.

---
 tree.c | 130 +++++++++++++++++++--------------------------------------
 1 file changed, 42 insertions(+), 88 deletions(-)

diff --git a/tree.c b/tree.c
index 6e1c0b2a..e58a7dca 100644
--- a/tree.c
+++ b/tree.c
@@ -3,7 +3,7 @@
 ** TecCGraf - PUC-Rio
 */
  
-char *rcs_tree="$Id: tree.c,v 1.5 1994/11/16 16:03:48 roberto Exp roberto $";
+char *rcs_tree="$Id: tree.c,v 1.6 1994/11/16 17:38:08 roberto Exp roberto $";
 
 
 #include <string.h>
@@ -17,13 +17,21 @@ char *rcs_tree="$Id: tree.c,v 1.5 1994/11/16 16:03:48 roberto Exp roberto $";
 #define lua_strcmp(a,b)	(a[0]<b[0]?(-1):(a[0]>b[0]?(1):strcmp(a,b))) 
 
 
-static TreeNode *string_root = NULL;
+typedef struct StringNode {
+  struct StringNode *next;
+  Word mark;
+  char str[1];
+} StringNode;
+
+static StringNode *string_root = NULL;
+
+
 static TreeNode *constant_root = NULL;
 
 /*
-** Insert a new string/constant/variable at the tree. 
+** Insert a new constant/variable at the tree. 
 */
-static TreeNode *tree_create (TreeNode **node, char *str, int *created)
+static TreeNode *tree_create (TreeNode **node, char *str)
 {
  if (*node == NULL)
  {
@@ -31,16 +39,15 @@ static TreeNode *tree_create (TreeNode **node, char *str, int *created)
   (*node)->left = (*node)->right = NULL;
   strcpy((*node)->str, str);
   (*node)->varindex = (*node)->constindex = UNMARKED_STRING;
-  *created = 1;
   return *node;
  }
  else
  {
   int c = lua_strcmp(str, (*node)->str);
   if (c < 0) 
-   return tree_create(&(*node)->left, str, created);
+   return tree_create(&(*node)->left, str);
   else if (c > 0)
-   return tree_create(&(*node)->right, str, created);
+   return tree_create(&(*node)->right, str);
   else
    return *node;
  }
@@ -48,101 +55,48 @@ static TreeNode *tree_create (TreeNode **node, char *str, int *created)
 
 char *lua_strcreate (char *str) 
 {
- int created=0;
- TreeNode *t = tree_create(&string_root, str, &created);
- if (created)
- {
+  StringNode *newString = (StringNode *)luaI_malloc(sizeof(StringNode)+
+                                                strlen(str));
+  newString->mark = UNMARKED_STRING;
+  strcpy(newString->str, str);
+  newString->next = string_root;
+  string_root = newString;
   if (lua_nentity == lua_block) lua_pack ();
   lua_nentity++;
- }
- return t->str;
+  return newString->str;
 }
 
+
 TreeNode *lua_constcreate (char *str) 
 {
- int created;
- return tree_create(&constant_root, str, &created);
-}
-
-
-/*
-** Free a node of the tree
-*/
-static TreeNode *lua_strfree (TreeNode *parent)
-{
- if (parent->left == NULL && parent->right == NULL) /* no child */
- {
-  luaI_free(parent);
-  return NULL;
- }
- else if (parent->left == NULL)         /* only right child */
- {
-  TreeNode *p = parent->right;
-  luaI_free(parent);
-  return p;
- }
- else if (parent->right == NULL)        /* only left child */
- {
-  TreeNode *p = parent->left;
-  luaI_free(parent);
-  return p;
- }
- else                                   /* two children */
- {
-  TreeNode *p = parent, *r = parent->right;
-  while (r->left != NULL)
-  {
-   p = r;
-   r = r->left;
-  }
-  if (p == parent)
-  {
-   r->left  = parent->left;
-   parent->left = NULL;
-   parent->right = r->right;
-   r->right = lua_strfree(parent);
-  }
-  else
-  {
-   TreeNode *t = r->right;
-   r->left  = parent->left;
-   r->right = parent->right;
-   parent->left = NULL;
-   parent->right = t;
-   p->left  = lua_strfree(parent);
-  }
-  return r;
- }
-}
-
-/*
-** Traverse tree for garbage collection
-*/
-static TreeNode *lua_travcollector (TreeNode *r)
-{
- if (r == NULL) return NULL;
- r->right = lua_travcollector(r->right);
- r->left  = lua_travcollector(r->left);
- if (r->constindex == UNMARKED_STRING) 
- {
-  ++lua_recovered;
-  return lua_strfree(r);
- }
- else
- {
-  r->constindex = UNMARKED_STRING;
-  return r;
- }
+ return tree_create(&constant_root, str);
 }
 
 
 /*
 ** Garbage collection function.
-** This function traverse the tree freening unindexed strings
+** This function traverse the string list freeing unindexed strings
 */
 void lua_strcollector (void)
 {
- string_root = lua_travcollector(string_root);
+  StringNode *curr = string_root, *prev = NULL;
+  while (curr)
+  {
+    StringNode *next = curr->next;
+    if (curr->mark == UNMARKED_STRING)
+    {
+      if (prev == NULL) string_root = next;
+      else prev->next = next;
+      luaI_free(curr);
+      ++lua_recovered;
+    }
+    else
+    {
+      curr->mark = UNMARKED_STRING;
+      prev = curr;
+    }
+    curr = next;
+  }
 }
 
 /*