83 lines
2.5 KiB
Rust
83 lines
2.5 KiB
Rust
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// SPDX-License-Identifier: LGPL-3.0-or-later
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// Copyright (c) 2024 Patrick_Pluto
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// This is an example implementation of a CPU emulator. You can copy this for your own custom ISA, or do something else.
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pub struct ExampleCPU {
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debug: bool,
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execution_pointer: u8,
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operands: [u8; 3],
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ram: [u8; 256],
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registers: [u8; 8],
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}
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impl ExampleCPU {
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// Here is where you can create your own CPU Instance.
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pub fn create_instance(debug: bool, initial_state: [u8; 256]) -> ExampleCPU {
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return ExampleCPU {
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debug: debug,
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execution_pointer: 0,
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operands: [0; 3],
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ram: initial_state,
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registers: [0; 8],
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};
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}
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// This fetches the operands, based on the position of the execution_pointer, then runs the selected instruction.
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pub fn fetch_and_decode(&mut self) {
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self.operands[0] = self.ram[self.execution_pointer as usize];
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self.operands[1] = self.ram[(self.execution_pointer + 1) as usize];
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self.operands[2] = self.ram[(self.execution_pointer + 2) as usize];
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println!(
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"0x{:02X} 0x{:02X} 0x{:02X}",
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self.operands[0], self.operands[1], self.operands[2]
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);
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match self.operands[0] {
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0x00 => self.nop(),
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0x01 => self.load(),
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0x02 => self.store(),
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0x03 => self.add(),
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0x04 => self.sub(),
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0x05 => self.jump(),
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0x06 => self.jpiz(),
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_ => self.nop(),
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};
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}
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// Here is where all of the implementations of the instructions should go.
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fn nop(&mut self) {
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self.execution_pointer += 1;
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}
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fn load(&mut self) {
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self.registers[self.operands[1] as usize] = self.ram[self.operands[2] as usize];
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self.execution_pointer += 3;
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}
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fn store(&mut self) {
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self.ram[self.operands[1] as usize] = self.registers[self.operands[2] as usize];
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self.execution_pointer += 3;
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}
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fn add(&mut self) {
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self.registers[self.operands[1] as usize] += self.registers[self.operands[2] as usize];
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self.execution_pointer += 3;
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}
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fn sub(&mut self) {
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self.registers[self.operands[1] as usize] -= self.registers[self.operands[2] as usize];
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self.execution_pointer += 3;
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}
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fn jump(&mut self) {
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self.execution_pointer = self.operands[1];
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}
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fn jpiz(&mut self) {
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if self.operands[2] == 0 {
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self.execution_pointer = self.operands[1];
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} else {
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self.execution_pointer += 3;
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}
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}
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}
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