116 lines
3.3 KiB
OCaml
116 lines
3.3 KiB
OCaml
(**
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* Copyright (c) 2015, Fabien Freling
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* All rights reserved.
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*
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* This source code is licensed under the BSD 2-clause license found in the
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* LICENSE file at the top level directory of this source tree.
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*)
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(** http://bgb.bircd.org/pandocs.htm#thecartridgeheader *)
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type memory_bank_controller =
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| ROM_ONLY
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| MBC1
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type t = {
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full_rom : bytes;
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nintendo_logo : bytes;
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title : string;
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mem_type : memory_bank_controller;
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rom_size : int;
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ram_size : int;
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(* header_checksum : bytes;
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global_checksum : bytes; *)
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}
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(** The Nintendo logo is a checksum in the header *)
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let check_nintendo_logo cartridge =
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let reference = Bytes.of_string
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"\xCE\xED\x66\x66\xCC\x0D\x00\x0B\x03\x73\x00\x83\x00\x0C\x00\x0D\
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\x00\x08\x11\x1F\x88\x89\x00\x0E\xDC\xCC\x6E\xE6\xDD\xDD\xD9\x99\
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\xBB\xBB\x67\x63\x6E\x0E\xEC\xCC\xDD\xDC\x99\x9F\xBB\xB9\x33\x3E" in
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(Bytes.compare cartridge.nintendo_logo reference) == 0
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let get_cartridge_type = function
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| 0x00 -> ROM_ONLY
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| 0x01 -> MBC1
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| x -> Printf.printf "%02X\n" x; failwith "Invalid cartridge type."
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let mem_type_name = function
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| ROM_ONLY -> "ROM_ONLY"
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| MBC1 -> "MBC1"
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(** ROM size is expressed in KB *)
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let get_ROM_size = function
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| 0x00 -> 32 (* no ROM banking *)
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| 0x01 -> 64 (* 4 banks *)
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| 0x02 -> 128 (* 8 banks *)
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| 0x03 -> 256 (* 16 banks *)
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| 0x04 -> 512 (* 32 banks *)
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| 0x05 -> 1000 (* 64 banks - only 63 banks used by MBC1 *)
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| 0x06 -> 2000 (* 128 banks - only 125 banks used by MBC1 *)
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| 0x07 -> 4000 (* 256 banks *)
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| 0x52 -> 1100 (* 72 banks *)
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| 0x53 -> 1200 (* 80 banks *)
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| 0x54 -> 1500 (* 96 banks *)
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| _ -> failwith "Invalid ROM size code."
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(** RAM size is expressed in KB *)
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let get_RAM_size = function
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| 0x00 -> 0
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| 0x01 -> 2
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| 0x02 -> 8
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| 0x03 -> 32 (* 4 x 8KB banks *)
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| _ -> failwith "Invalid RAM size code."
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let read_cartridge file =
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try
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let ic = open_in_bin file in
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let file_size = in_channel_length ic in
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let full_rom = Bytes.create file_size in
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really_input ic full_rom 0 file_size;
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close_in ic;
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(* Nintendo logo *)
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let nin_logo_offset = 0x0104 in
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let nin_logo_size = 48 in
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let nintendo_logo = Bytes.sub full_rom nin_logo_offset nin_logo_size in
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(* Title *)
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let title_offset = 0x0134 in
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let title_size = 16 in
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let title_b = Bytes.sub full_rom title_offset title_size in
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let title = Bytes.to_string title_b in
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(* Cartridge type - memory bank *)
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let mem_type_code = Bytes.get full_rom 0x0147 |> int_of_char in
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let mem_type = get_cartridge_type mem_type_code in
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(* ROM size *)
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let rom_size_code = Bytes.get full_rom 0x0148 |> int_of_char in
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let rom_size = get_ROM_size rom_size_code in
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(* RAM size *)
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let ram_size_code = Bytes.get full_rom 0x0149 |> int_of_char in
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let ram_size = get_RAM_size ram_size_code in
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Some { full_rom; nintendo_logo; title; mem_type; rom_size; ram_size }
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with
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| Sys_error msg
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| Invalid_argument msg (* This is triggered by Bytes.sub *)
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| Failure msg -> prerr_endline msg; None
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let print_info cartridge =
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let open Printf in
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printf "Title: %s\n" cartridge.title;
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printf "Mem. type: %s\n" (cartridge.mem_type |> mem_type_name);
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printf "ROM size: %iKB\n" cartridge.rom_size;
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printf "RAM size: %iKB\n" cartridge.ram_size
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