From 6fb3849e73b797d4610a2b782127f927dec0c9c9 Mon Sep 17 00:00:00 2001
From: Alejandro Soto <alejandro@34project.org>
Date: Mon, 14 Nov 2022 21:10:40 -0600
Subject: Implement VGA simulation

---
 tb/mem.impl.hpp | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)
 create mode 100644 tb/mem.impl.hpp

(limited to 'tb/mem.impl.hpp')

diff --git a/tb/mem.impl.hpp b/tb/mem.impl.hpp
new file mode 100644
index 0000000..f7bb424
--- /dev/null
+++ b/tb/mem.impl.hpp
@@ -0,0 +1,81 @@
+#ifndef TALLER_MEM_IMPL_HPP
+#define TALLER_MEM_IMPL_HPP
+
+#include <cassert>
+#include <cstdint>
+#include <memory>
+
+namespace taller::avalon
+{
+	template<typename Cell>
+	mem<Cell>::mem(std::uint32_t base, std::uint32_t size)
+	: slave(base, size, sizeof(Cell)),
+	  block(std::make_unique<Cell[]>(size >> word_bits()))
+	{}
+
+	template<typename Cell>
+	template<typename F>
+	void mem<Cell>::load(F loader, std::size_t offset)
+	{
+		auto base = base_address();
+		auto bits = word_bits();
+		std::size_t size = address_span();
+		std::size_t addr = base_address() + offset;
+
+		while(addr >= base && addr < base + size)
+		{
+			std::size_t read = loader(&block[(addr - base) >> bits], (base + size - addr) >> bits);
+			if(read == 0)
+			{
+				break;
+			}
+
+			addr += read << bits;
+		}
+	}
+
+	template<typename Cell>
+	bool mem<Cell>::read(std::uint32_t addr, std::uint32_t &data)
+	{
+		data = block[addr];
+		return ready();
+	}
+
+	template<typename Cell>
+	bool mem<Cell>::write(std::uint32_t addr, std::uint32_t data, unsigned byte_enable)
+	{
+		std::uint32_t bytes = 0;
+
+		if(byte_enable & 0b1000)
+		{
+			bytes |= 0xff << 24;
+		}
+
+		if(byte_enable & 0b0100)
+		{
+			bytes |= 0xff << 16;
+		}
+
+		if(byte_enable & 0b0010)
+		{
+			bytes |= 0xff << 8;
+		}
+
+		if(byte_enable & 0b0001)
+		{
+			bytes |= 0xff;
+		}
+
+		block[addr] = (data & bytes) | (block[addr] & ~bytes);
+		return ready();
+	}
+
+	template<typename Cell>
+	bool mem<Cell>::ready() noexcept
+	{
+		count = count > 0 ? count - 1 : 2;
+		return count == 0;
+	}
+}
+
+#endif
-- 
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