initial commit: load cartridge, parse instr types

.editorconfig

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+root = true
+
+[*.cr]
+charset = utf-8
+end_of_line = lf
+insert_final_newline = true
+indent_style = space
+indent_size = 2
+trim_trailing_whitespace = true

.gitignore

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+/docs/
+/lib/
+/bin/
+/.shards/
+*.dwarf

.travis.yml

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+language: crystal
+
+# Uncomment the following if you'd like Travis to run specs and check code formatting
+# script:
+#   - crystal spec
+#   - crystal tool format --check

LICENSE

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+The MIT License (MIT)
+
+Copyright (c) 2020 your-name-here
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.

README.md

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+# crab
+
+TODO: Write a description here
+
+## Installation
+
+TODO: Write installation instructions here
+
+## Usage
+
+TODO: Write usage instructions here
+
+## Development
+
+TODO: Write development instructions here
+
+## Contributing
+
+1. Fork it (<https://github.com/your-github-user/crab/fork>)
+2. Create your feature branch (`git checkout -b my-new-feature`)
+3. Commit your changes (`git commit -am 'Add some feature'`)
+4. Push to the branch (`git push origin my-new-feature`)
+5. Create a new Pull Request
+
+## Contributors
+
+- [your-name-here](https://github.com/your-github-user) - creator and maintainer

shard.yml

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+name: crab
+version: 0.1.0
+
+authors:
+  - Matthew Berry <me@mattrb.com>
+
+targets:
+  crab:
+    main: src/crab.cr
+
+crystal: 0.35.1
+
+license: MIT

spec/crab_spec.cr

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+require "./spec_helper"
+
+describe Crab do
+  # TODO: Write tests
+
+  it "works" do
+    false.should eq(true)
+  end
+end

spec/spec_helper.cr

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+require "spec"
+require "../src/crab"

src/crab.cr

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+require "./crab/gba"
+
+module Crab
+  VERSION = "0.1.0"
+
+  extend self
+
+  def run
+    gba = GBA.new ARGV[0]
+    gba.run
+  end
+end
+
+unless PROGRAM_NAME.includes?("crystal-run-spec")
+  Crab.run
+end

src/crab/bus.cr

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+class Bus
+  CARTRIDGE = 0x08000000..0x0FFFFFFF
+  UNUSED    = 0x10000000..0xFFFFFFFF
+
+  def initialize(@gba : GBA)
+  end
+
+  def [](index : Int) : Byte
+    # puts "read #{hex_str index.to_u32}"
+    case index
+    when CARTRIDGE then @gba.cartridge[index - CARTRIDGE.begin]
+    when UNUSED    then 0xFF
+    else                0xFF
+    end.to_u8
+  end
+
+  def read_word(index : Int) : Word
+    self[index].to_u32 |
+      (self[index + 1].to_u32 << 8) |
+      (self[index + 2].to_u32 << 16) |
+      (self[index + 3].to_u32 << 24)
+  end
+
+  def []=(index : Int, value : Byte) : Nil
+    # puts "write #{hex_str index.to_u32} -> #{hex_str value}"
+    case index
+    when CARTRIDGE then @gba.cartridge[index]
+    when UNUSED    then nil
+    else                @todo[index] = value
+    end
+  end
+
+  def []=(index : Int, value : Word) : Nil
+    # puts "write #{hex_str index.to_u32} -> #{hex_str value}"
+    self[index] = 0xFF_u8 & (value >> 24)
+    self[index] = 0xFF_u8 & (value >> 16)
+    self[index] = 0xFF_u8 & (value >> 8)
+    self[index] = 0xFF_u8 & value
+  end
+end

src/crab/cartridge.cr

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+class Cartridge
+  @rom : Bytes
+
+  getter title : String {
+    io = IO::Memory.new
+    io.write @rom[0x0A0...0x0AC]
+    io.to_s
+  }
+
+  def initialize(rom_path : String)
+    @rom = File.open rom_path do |file|
+      bytes = Bytes.new file.size
+      file.read bytes
+      bytes
+    end
+  end
+
+  def [](index : Int) : Byte
+    @rom[index]
+  end
+
+  def []=(index : Int, value : Byte) : Nil
+  end
+end

src/crab/cpu.cr

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+class CPU
+  @registers = Slice(UInt32).new 16
+
+  def initialize(@gba : GBA)
+    self.pc = 0x08000000
+  end
+
+  def pc : Word
+    @registers[15]
+  end
+
+  def pc=(pc : Word) : Nil
+    @registers[15] = pc
+  end
+
+  def tick : Nil
+    puts "PC: #{hex_str pc}, INSTRUCTION: #{hex_str @gba.bus.read_word pc}, TYPE: #{Instr.from_hash hash_instr @gba.bus.read_word pc}"
+    # puts hex_str @gba.bus.read_word pc
+    # puts hex_str hash_instr @gba.bus.read_word pc
+    # puts Instr.from_hash hash_instr @gba.bus.read_word pc
+    self.pc += 4
+  end
+
+  def hash_instr(instr : Word) : Word
+    ((instr >> 16) & 0x0FF0) | ((instr >> 4) & 0xF)
+  end
+end

src/crab/gba.cr

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+require "./types"
+require "./util"
+require "./cartridge"
+require "./bus"
+require "./cpu"
+
+class GBA
+  getter cartridge : Cartridge
+  getter bus : Bus { Bus.new self }
+  getter cpu : CPU { CPU.new self }
+
+  def initialize(rom_path : String)
+    @cartridge = Cartridge.new rom_path
+  end
+
+  def run : Nil
+    # puts @cartridge.title
+    loop do
+      cpu.tick
+    end
+  end
+end

src/crab/types.cr

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+alias Byte = UInt8
+alias Word = UInt32
+alias Words = Slice(UInt32)
+
+enum Instr
+  DATA_PROCESSING_PSR_TRANSFER
+  MULTIPLY
+  MULTIPLY_LONG
+  SINGLE_DATA_SWAP
+  BRANCH_EXCHANGE
+  HALFWORD_DATA_TRANSFER_REGISTER_OFFSET
+  HALFWORD_DATA_TRANSFER_IMMEDIATE_OFFSET
+  SINGLE_DATA_TRANSFER
+  UNDEFINED
+  BLOCK_DATA_TRANSFER
+  BRANCH
+  COPROCESSOR_DATA_TRANSFER
+  COPROCESSOR_DATA_OPERATION
+  COPROCESSOR_REGISTER_TRANSFER
+  SOFTWARE_INTERRUPT
+
+  def self.from_hash(hash : Word) : Instr
+    if hash & 0b111100000000 == 0b111100000000
+      SOFTWARE_INTERRUPT
+    elsif hash & 0b111100000001 == 0b111000000001
+      COPROCESSOR_REGISTER_TRANSFER
+    elsif hash & 0b111100000001 == 0b111000000001
+      COPROCESSOR_DATA_OPERATION
+    elsif hash & 0b111000000000 == 0b110000000000
+      COPROCESSOR_DATA_TRANSFER
+    elsif hash & 0b111000000000 == 0b101000000000
+      BRANCH
+    elsif hash & 0b111000000000 == 0b100000000000
+      BLOCK_DATA_TRANSFER
+    elsif hash & 0b111000000001 == 0b011000000001
+      UNDEFINED
+    elsif hash & 0b110000000000 == 0b010000000000
+      SINGLE_DATA_TRANSFER
+    elsif hash & 0b111001001001 == 0b000001001001
+      HALFWORD_DATA_TRANSFER_IMMEDIATE_OFFSET
+    elsif hash & 0b111001001001 == 0b000000001001
+      HALFWORD_DATA_TRANSFER_REGISTER_OFFSET
+    elsif hash & 0b111111111111 == 0b000100100001
+      BRANCH_EXCHANGE
+    elsif hash & 0b111110111111 == 0b000100001001
+      SINGLE_DATA_SWAP
+    elsif hash & 0b111110001111 == 0b000010001001
+      MULTIPLY_LONG
+    elsif hash & 0b111111001111 == 0b000000001001
+      MULTIPLY
+    elsif hash & 0b110000000000 == 0b000000000000
+      DATA_PROCESSING_PSR_TRANSFER
+    else
+      raise "Unimplemented from_hash #{hex_str hash}"
+    end
+  end
+end

src/crab/util.cr

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+def hex_str(n : UInt8 | UInt16 | UInt32 | UInt64) : String
+  "0x#{n.to_s(16).rjust(sizeof(typeof(n)) * 2, '0').upcase}"
+end
+
+def bit?(value : Int, bit : Int) : Bool
+  (value >> bit) & 1 > 0
+end
+
+def set_bit(value : Int, bit : Int) : Nil
+  value | 1 << bit
+end
+
+def clear_bit(value : Int, bit : Int) : Nil
+  value & ~(1 << bit)
+end