--- parser3/src/include/pa_stack.h	2001/02/22 13:33:24	1.2
+++ parser3/src/include/pa_stack.h	2026/04/25 13:38:46	1.35
@@ -1,40 +1,57 @@
-/*
-  $Id: pa_stack.h,v 1.2 2001/02/22 13:33:24 paf Exp $
+/** @file
+	Parser: stack class decl.
+
+	Copyright (c) 2001-2026 Art. Lebedev Studio (https://www.artlebedev.com)
+	Authors: Konstantin Morshnev <moko@design.ru>, Alexandr Petrosian <paf@design.ru>
 */
 
 #ifndef PA_STACK_H
 #define PA_STACK_H
 
+#define IDENT_PA_STACK_H "$Id: pa_stack.h,v 1.35 2026/04/25 13:38:46 moko Exp $"
+
 #include "pa_array.h"
 
-class Stack : public Array {
+/// simple stack based on Array
+template<typename T> class Stack: public Array<T> {
 public:
 
-	Stack(Pool& apool) : Array(apool), ftop(0) {
-	}
+	Stack(size_t initial=4) : Array<T>(initial){}
 
-	void push(Item *item) {
-		if(ftop<size()) // cell is already allocated?
-			put(ftop, item); // use it
-		else
-			*this+=item; // append it
-		ftop++;
-	}
-	Item *pop() {
-		return get(--ftop);
+	inline void push(T item) {
+		if(this->is_full())
+			expand(this->fallocated); // free is not called, so expanding a lot to decrease memory waste
+		this->felements[this->fsize++]=item;
 	}
 
-	Item *operator [] (int top_offset) {
-		return get(ftop-top_offset-1);
+	inline T pop() {
+		return this->felements[--this->fsize];
 	}
 
-	int top() { return ftop; }
+	inline bool is_empty() { return this->fsize==0; }
+	inline size_t top_index() { return this->fsize; }
+	inline void set_top_index(size_t atop) { this->fsize=atop; }
+	inline T top_value() {
+		assert(!is_empty());
+		return this->felements[this->fsize-1];
+	}
 
-private:
+	/// call this prior to collecting garbage [in unused part of stack there may be pointers(unused)]
+	void wipe_unused() {
+		if(size_t above_top_size=this->fallocated-this->fsize)
+			memset((void *)&this->felements[this->fsize], 0, above_top_size*sizeof(T));
+	}
 
-	// deepest used index
-	int ftop;
+protected:
 
+	void expand(size_t delta) {
+		size_t new_allocated=this->fallocated+delta;
+		// we can't use realloc as MethodParams references allocated stack
+		T* new_elements = (T *)pa_malloc(new_allocated*sizeof(T));
+		memcpy(new_elements, this->felements, this->fallocated*sizeof(T));
+		this->felements=new_elements;
+		this->fallocated=new_allocated;
+	}
 };
 
 #endif