File _service:obs_scm:CVE-2021-33391-pre.patch of Package tidy

Origin: https://launchpadlibrarian.net/697070499/tidy-html5_2%3A5.6.0-11_2%3A5.6.0-11ubuntu0.20.04.1.diff.gz
Partial backport of:

From e56716f154f13b14fc5585146a85000fdd26d319 Mon Sep 17 00:00:00 2001
From: Jim Derry <balthisar@gmail.com>
Date: Wed, 28 Jul 2021 19:45:57 -0400
Subject: [PATCH] Improve internal documentation. Start general conversion to
 eliminate and/or reduce recursion.

--- a/src/lexer.c
+++ b/src/lexer.c
@@ -4425,6 +4425,106 @@ static Node *ParseDocTypeDecl(TidyDocImp
     return NULL;
 }
 
+
+/****************************************************************************//*
+ ** MARK: - Node Stack
+ ***************************************************************************/
+
+
+/**
+ * Create a new stack with a given starting capacity. If memory allocation
+ * fails, then the allocator will panic the program automatically.
+ */
+Stack* TY_(newStack)(TidyDocImpl *doc, uint capacity)
+{
+    Stack *stack = (Stack *)TidyAlloc(doc->allocator, sizeof(Stack));
+    stack->top = -1;
+    stack->capacity = capacity;
+    stack->firstNode = (Node **)TidyAlloc(doc->allocator, stack->capacity * sizeof(Node**));
+    stack->allocator = doc->allocator;
+    return stack;
+}
+ 
+
+/**
+ *  Increase the stack size. This will be called automatically when the
+ *  current stack is full. If memory allocation fails, then the allocator
+ *  will panic the program automatically.
+ */
+void TY_(growStack)(Stack *stack)
+{
+    uint new_capacity = stack->capacity * 2;
+    
+    Node **firstNode = (Node **)TidyAlloc(stack->allocator, new_capacity);
+    
+    memcpy( firstNode, stack->firstNode, sizeof(Node**) * (stack->top + 1) );
+    TidyFree(stack->allocator, stack->firstNode);
+
+    stack->firstNode = firstNode;
+    stack->capacity = new_capacity;
+}
+
+
+/**
+ * Stack is full when top is equal to the last index.
+ */
+Bool TY_(stackFull)(Stack *stack)
+{
+    return stack->top == stack->capacity - 1;
+}
+
+
+/**
+ * Stack is empty when top is equal to -1
+ */
+Bool TY_(stackEmpty)(Stack *stack)
+{
+    return stack->top == -1;
+}
+ 
+
+/**
+ * Push an item to the stack.
+ */
+void TY_(push)(Stack *stack, Node *node)
+{
+    if (TY_(stackFull)(stack))
+        TY_(growStack)(stack);
+    
+    if (node)
+        stack->firstNode[++stack->top] = node;
+}
+
+
+/**
+ * Pop an item from the stack.
+ */
+Node* TY_(pop)(Stack *stack)
+{
+    return TY_(stackEmpty)(stack) ? NULL : stack->firstNode[stack->top--];
+}
+
+
+/**
+ * Peek at the stack.
+ */
+FUNC_UNUSED Node* TY_(peek)(Stack *stack)
+{
+    return TY_(stackEmpty)(stack) ? NULL : stack->firstNode[stack->top--];
+}
+
+/**
+ *  Frees the stack when done.
+ */
+void TY_(freeStack)(Stack *stack)
+{
+    TidyFree( stack->allocator, stack->firstNode );
+    stack->top = -1;
+    stack->capacity = 0;
+    stack->firstNode = NULL;
+    stack->allocator = NULL;
+}
+
 /*
  * local variables:
  * mode: c
--- a/src/lexer.h
+++ b/src/lexer.h
@@ -594,6 +594,78 @@ Node* TY_(InsertedToken)( TidyDocImpl* d
 TY_PRIVATE Bool TY_(SwitchInline)( TidyDocImpl* doc, Node* element, Node* node );
 TY_PRIVATE Bool TY_(InlineDup1)( TidyDocImpl* doc, Node* node, Node* element );
 
+/** @}
+ *  @name Generic stack of nodes.
+ *  @{
+ */
+
+
+/**
+ * This typedef represents a stack of addresses to nodes. Tidy uses these to
+ * try to limit recursion by pushing nodes to a stack when possible instead
+ * of recursing.
+ */
+typedef struct _Stack {
+    int top;                        /**< Current top position. */
+    unsigned capacity;              /**< Current capacity. Can be expanded. */
+    Node **firstNode;               /** A pointer to the first pointer to a Node in an array of node addresses. */
+    TidyAllocator* allocator;       /**< Tidy's allocator, used at instantiation and expanding. */
+} Stack;
+ 
+
+/**
+ * Create a new stack with a given starting capacity. If memory allocation
+ * fails, then the allocator will panic the program automatically.
+ */
+Stack* TY_(newStack)(TidyDocImpl *doc, uint capacity);
+ 
+
+/**
+ *  Increase the stack size. This will be called automatically when the
+ *  current stack is full. If memory allocation fails, then the allocator
+ *  will panic the program automatically.
+ */
+void TY_(growStack)(Stack *stack);
+
+
+/**
+ * Stack is full when top is equal to the last index.
+ */
+Bool TY_(stackFull)(Stack *stack);
+
+
+/**
+ * Stack is empty when top is equal to -1
+ */
+Bool TY_(stackEmpty)(Stack *stack);
+ 
+
+/**
+ * Push an item to the stack.
+ */
+void TY_(push)(Stack *stack, Node *node);
+
+
+/**
+ * Pop an item from the stack.
+ */
+Node* TY_(pop)(Stack *stack);
+
+
+/**
+ * Peek at the stack.
+ */
+Node* TY_(peek)(Stack *stack);
+
+/**
+ *  Frees the stack when done.
+ */
+void TY_(freeStack)(Stack *stack);
+
+
+/** @}
+ */
+
 #ifdef __cplusplus
 }
 #endif