added fixed-size stack implementation

README.md

@@ -142,6 +142,10 @@ A [Digital delay line](https://en.wikipedia.org/wiki/Digital_delay_line) can be
 
 A [ring buffer](https://en.wikipedia.org/wiki/Circular_buffer) based, fixed-size [double-ended queue](https://en.wikipedia.org/wiki/Double-ended_queue).
 
+### [stack.hh](stack.hh)
+
+A fixed-size [stack](https://en.wikipedia.org/wiki/Stack_(abstract_data_type)) with access to the first element.
+
 ### [calculus.hh](calculus.hh)
 
 Some [calculus](https://en.wikipedia.org/wiki/Calculus) functions:

stack.hh

@@ -0,0 +1,63 @@
+/*
+Fixed-size stack
+
+Copyright 2020 Ahmet Inan <inan@aicodix.de>
+*/
+
+#pragma once
+
+namespace DSP {
+
+template <typename TYPE, int SIZE>
+class Stack
+{
+	TYPE buf[SIZE];
+	int pos;
+public:
+	Stack() : pos(-1)
+	{
+	}
+	void clear()
+	{
+		pos = -1;
+	}
+	void push(TYPE input)
+	{
+		assert(pos < SIZE-1);
+		buf[++pos] = input;
+	}
+	void pop()
+	{
+		assert(pos >= 0);
+		--pos;
+	}
+	TYPE top()
+	{
+		assert(pos >= 0);
+		return buf[pos];
+	}
+	TYPE first()
+	{
+		assert(pos >= 0);
+		return buf[0];
+	}
+	bool empty()
+	{
+		return pos == -1;
+	}
+	bool full()
+	{
+		return pos == SIZE-1;
+	}
+	int size()
+	{
+		return pos+1;
+	}
+	int max_size()
+	{
+		return SIZE;
+	}
+};
+
+}
+