From 025622f7ba344b1e47dd47c92ed380902ecbddfd Mon Sep 17 00:00:00 2001
From: Bent Bisballe Nyeng <deva@aasimon.org>
Date: Sun, 6 Aug 2023 18:18:31 +0200
Subject: A6: WIP (code is done)

---
 a6/custom.cc | 128 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 128 insertions(+)
 create mode 100644 a6/custom.cc

(limited to 'a6/custom.cc')

diff --git a/a6/custom.cc b/a6/custom.cc
new file mode 100644
index 0000000..4b95e0b
--- /dev/null
+++ b/a6/custom.cc
@@ -0,0 +1,128 @@
+#include <iostream>
+#include <functional>
+#include <limits>
+#include <memory>
+#include <vector>
+#include <cstddef>
+#include <memory>
+
+#include "generator_stack.h"
+
+void* operator new([[maybe_unused]]std::size_t n)
+{
+	std::cout << "new\n";
+	throw std::bad_alloc();
+}
+
+void operator delete(void*) throw()
+{
+	std::cout << "delete\n";
+	// Do nothing. actual memory is allocated on the stack
+}
+
+void operator delete(void*, std::size_t) throw()
+{
+	std::cout << "delete[]\n";
+	// Do nothing. actual memory is allocated on the stack
+}
+
+// Code heavily inspired by:
+//  https://stackoverflow.com/questions/66891368/template-parametric-type-allocator-in-c
+template <typename T, std::size_t S>
+struct StackAllocator
+{
+	using value_type = T;
+	using size_type = size_t;
+	using pointer = value_type*;
+
+	template<class U> struct rebind { using other = StackAllocator<U, S>; };
+
+	StackAllocator() = default;
+	StackAllocator(const StackAllocator&) = default;
+	template <typename U> StackAllocator(const StackAllocator<U, S>&) {}
+
+	pointer allocate(size_type n)
+	{
+		if(n > S) throw std::bad_alloc();
+		return buf;
+	}
+
+	void deallocate(void*, size_type)
+	{
+	}
+
+private:
+	T buf[S];
+};
+
+template<typename T>
+Generator<T, 64> iota(T start)
+{
+	while(true)
+	{
+		co_yield start++;
+	}
+}
+
+int main()
+{
+	std::cout << " ** std::string:\n";
+	{
+		std::basic_string<char, std::char_traits<char>, StackAllocator<char, 32>> str(31, 'a');
+		std::cout << str << " " << sizeof(str) << '\n';
+
+		std::basic_string<char, std::char_traits<char>, StackAllocator<char, 64>> str2(31, 'a');
+		std::cout << str2 << " " << sizeof(str2) << '\n';
+	}
+	std::cout << '\n';
+
+	std::cout << " ** std::vector:\n";
+	{
+		try
+		{
+			std::vector<int, StackAllocator<int, 10>> vec{42};
+		}
+		catch(std::bad_alloc &e)
+		{
+			std::cout << "No SBO for std::vector!\n";
+		}
+	}
+	std::cout << '\n';
+
+
+	std::cout << " ** std::function:\n";
+	{
+//		{ // Support for allocators with std::function removed in C++17
+//			std::function<std::allocator_arg, StackAllocator<int, 10>, int()> f;
+//			char foo[16]{};
+//			f = [foo]() // capture up to 16 bytes is ok for std::function
+//			    {
+//				    int i = 0;
+//				    for(auto v : foo) i += v;
+//				    return i;
+//			    };
+//		}
+	}
+	std::cout << '\n';
+
+
+	std::cout << " ** co-routines:\n";
+	{
+		try
+		{
+			auto gen = iota(0);
+			while(true)
+			{
+				auto i = gen();
+				if(i > 10) break;
+				std::cout << i << " ";
+			}
+			std::cout << '\n';
+		}
+		catch(std::bad_alloc &e)
+		{
+			std::cout << "Co-routines always allocate!\n";
+		}
+	}
+	std::cout << '\n';
+}
-- 
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