Read Nintendo checksum in cartridge header.

This first commit parses the ROM to extract the Nintendo Logo and
display it on stdout.

.gitignore

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+# vim
+.*.swp
+
+# OCaml
+_build
+*.byte
+*.native

LICENSE

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+Copyright (c) 2015, Fabien Freling
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+* Redistributions of source code must retain the above copyright notice, this
+  list of conditions and the following disclaimer.
+
+* Redistributions in binary form must reproduce the above copyright notice,
+  this list of conditions and the following disclaimer in the documentation
+  and/or other materials provided with the distribution.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
+CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+

Makefile

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+all:
+	ocamlbuild -use-ocamlfind -I src oboy.byte

_tags

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+true: package(unix)

src/cartridge.ml

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+open Unix
+open Printf
+
+(** http://bgb.bircd.org/pandocs.htm#thecartridgeheader *)
+
+type memory_bank_controller =
+  | ROM_ONLY
+  | MBC1
+
+type t = {
+  nintendo_logo : bytes;
+  title : string;
+  mem_type : memory_bank_controller;
+  rom_size : int;
+  ram_size : int;
+  header_checksum : bytes;
+  global_checksum : bytes;
+}
+
+let read_cartridge file =
+  print_endline file;
+  let fd = openfile file [Unix.O_RDONLY] 0o644 in
+  let n_logo = Bytes.create 48 in
+  let _ = lseek fd 0x0104 SEEK_SET in
+  let _ = read fd n_logo 0 48 in
+  print_endline "Nintendo logo:";
+  Hexa.print_bytes n_logo ~width:16;
+  Unix.close fd

src/hexa.ml

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+open Printf
+
+let print_bytes b ?(width=8) =
+  let l = Bytes.length b in
+  let rec print_line b start last =
+    if start < last then
+      let max = min (start + width - 1) last in
+      for i = start to max do
+        printf "%02X " (Bytes.get b i |> int_of_char)
+      done;
+      print_newline ();
+      print_line b (start + width) last
+  in
+  print_line b 0 l

src/oboy.ml

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+let () =
+  if Array.length Sys.argv < 2
+  then print_endline "Please specify a ROM."
+  else Cartridge.read_cartridge Sys.argv.(1)