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fingerprint.go
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fingerprint.go
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// This file is part of Gopher2600.
//
// Gopher2600 is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Gopher2600 is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Gopher2600. If not, see <https://www.gnu.org/licenses/>.
package cartridge
import (
"github.com/jetsetilly/gopher2600/cartridgeloader"
"github.com/jetsetilly/gopher2600/curated"
"github.com/jetsetilly/gopher2600/hardware/memory/cartridge/harmony/cdf"
"github.com/jetsetilly/gopher2600/hardware/memory/cartridge/harmony/dpcplus"
"github.com/jetsetilly/gopher2600/hardware/memory/cartridge/mapper"
"github.com/jetsetilly/gopher2600/hardware/memory/cartridge/supercharger"
"github.com/jetsetilly/gopher2600/logger"
)
func fingerprint3e(b []byte) bool {
// 3E cart bankswitching is triggered by storing the bank number in address
// 3E using 'STA $3E', commonly followed by an immediate mode LDA
//
// fingerprint method taken from:
//
// https://gitlab.com/firmaplus/atari-2600-pluscart/-/blob/master/source/STM32firmware/PlusCart/Src/cartridge_detection.c#L140
for i := 0; i < len(b)-3; i++ {
if b[i] == 0x85 && b[i+1] == 0x3e && b[i+2] == 0xa9 && b[i+3] == 0x00 {
return true
}
}
return false
}
func fingerprint3ePlus(b []byte) bool {
// previous versions of this function worked similarly to the tigervision
// method but this is more accurate
//
// fingerprint method taken from:
//
// https://gitlab.com/firmaplus/atari-2600-pluscart/-/blob/master/source/STM32firmware/PlusCart/Src/cartridge_detection.c#L148
for i := 0; i < len(b)-3; i++ {
if b[i] == 'T' && b[i+1] == 'J' && b[i+2] == '3' && b[i+3] == 'E' {
return true
}
}
return false
}
func fingerprintMnetwork(b []byte) bool {
// Bump 'n' Jump is the fussiest mnetwork cartridge I've found. Matching
// hotspots:
//
// $fdd5 LDA BANK5
// $fde3 LDA BANK6
// $fe0e LDA BANK5
// $fe16 LDA BANK4
//
// This also catches modern games not created by mnetwork, eg Pitkat
threshold := 4
for i := 0; i < len(b)-3; i++ {
if b[i] == 0xad && b[i+2] == 0xff && (b[i+1] == 0xe4 || b[i+1] == 0xe5 || b[i+1] == 0xe6) {
threshold--
}
if threshold == 0 {
return true
}
}
return false
}
func fingerprintParkerBros(b []byte) bool {
// fingerprint patterns taken from Stella CartDetector.cxx
for i := 0; i <= len(b)-3; i++ {
if (b[i] == 0x8d && b[i+1] == 0xe0 && b[i+2] == 0x1f) ||
(b[i] == 0x8d && b[i+1] == 0xe0 && b[i+2] == 0x5f) ||
(b[i] == 0x8d && b[i+1] == 0xe9 && b[i+2] == 0xff) ||
(b[i] == 0x0c && b[i+1] == 0xe0 && b[i+2] == 0x1f) ||
(b[i] == 0xad && b[i+1] == 0xe0 && b[i+2] == 0x1f) ||
(b[i] == 0xad && b[i+1] == 0xe9 && b[i+2] == 0xff) ||
(b[i] == 0xad && b[i+1] == 0xed && b[i+2] == 0xff) ||
(b[i] == 0xad && b[i+1] == 0xf3 && b[i+2] == 0xbf) {
return true
}
}
return false
}
func fingerprintDF(b []byte) bool {
if len(b) < 0xffb {
return false
}
return b[0xff8] == 'D' && b[0xff9] == 'F' && b[0xffa] == 'S' && b[0xffb] == 'C'
}
func fingerprintDPCplus(b []byte) bool {
if len(b) < 0x23 {
return false
}
return b[0x20] == 0x1e && b[0x21] == 0xab && b[0x22] == 0xad && b[0x23] == 0x10
}
func fingerprintCDF(b []byte) (bool, byte) {
count := 0
version := byte(0)
for i := 0; i < len(b)-3; i++ {
if b[i] == 'C' && b[i+1] == 'D' && b[i+2] == 'F' {
count++
version = b[i+3]
}
}
return count >= 3, version
}
func fingerprintSuperchargerFastLoad(cartload cartridgeloader.Loader) bool {
l := len(cartload.Data)
return l == 8448 || l == 25344 || l == 33792
}
func fingerprintTigervision(b []byte) bool {
// tigervision cartridges change banks by writing to memory address 0x3f. we
// can hypothesise that these types of cartridges will have that instruction
// sequence "85 3f" many times in a ROM whereas other cartridge types will not
threshold := 5
for i := 0; i < len(b)-1; i++ {
if b[i] == 0x85 && b[i+1] == 0x3f {
threshold--
}
if threshold == 0 {
return true
}
}
return false
}
func fingerprint8k(data []byte) func([]byte) (mapper.CartMapper, error) {
if fingerprintTigervision(data) {
return newTigervision
}
if fingerprintParkerBros(data) {
return newParkerBros
}
return newAtari8k
}
func fingerprint16k(data []byte) func([]byte) (mapper.CartMapper, error) {
if fingerprintTigervision(data) {
return newTigervision
}
if fingerprintMnetwork(data) {
return newMnetwork
}
return newAtari16k
}
func fingerprint32k(data []byte) func([]byte) (mapper.CartMapper, error) {
if fingerprintTigervision(data) {
return newTigervision
}
return newAtari32k
}
func fingerprint128k(data []byte) func([]byte) (mapper.CartMapper, error) {
if fingerprintDF(data) {
return newDF
}
logger.Log("fingerprint", "not confident that this is DF file")
return newDF
}
func (cart *Cartridge) fingerprint(cartload cartridgeloader.Loader) error {
var err error
if ok, version := fingerprintCDF(cartload.Data); ok {
cart.mapper, err = cdf.NewCDF(version, cartload.Data)
return err
}
if fingerprintDPCplus(cartload.Data) {
cart.mapper, err = dpcplus.NewDPCplus(cartload.Data)
return err
}
if fingerprintSuperchargerFastLoad(cartload) {
cart.mapper, err = supercharger.NewSupercharger(cartload)
return err
}
if fingerprint3e(cartload.Data) {
cart.mapper, err = new3e(cartload.Data)
return err
}
if fingerprint3ePlus(cartload.Data) {
cart.mapper, err = new3ePlus(cartload.Data)
return err
}
switch len(cartload.Data) {
case 2048:
cart.mapper, err = newAtari2k(cartload.Data)
if err != nil {
return err
}
case 4096:
cart.mapper, err = newAtari4k(cartload.Data)
if err != nil {
return err
}
case 8192:
cart.mapper, err = fingerprint8k(cartload.Data)(cartload.Data)
if err != nil {
return err
}
case 10240:
fallthrough
case 10495:
cart.mapper, err = newDPC(cartload.Data)
if err != nil {
return err
}
case 12288:
cart.mapper, err = newCBS(cartload.Data)
if err != nil {
return err
}
case 16384:
cart.mapper, err = fingerprint16k(cartload.Data)(cartload.Data)
if err != nil {
return err
}
case 32768:
cart.mapper, err = fingerprint32k(cartload.Data)(cartload.Data)
if err != nil {
return err
}
case 65536:
return curated.Errorf("65536 bytes not yet supported")
case 131072:
cart.mapper, err = fingerprint128k(cartload.Data)(cartload.Data)
if err != nil {
return err
}
default:
return curated.Errorf("unrecognised size (%d bytes)", len(cartload.Data))
}
// if cartridge mapper implements the optionalSuperChip interface then try
// to add the additional RAM
if superchip, ok := cart.mapper.(mapper.OptionalSuperchip); ok {
superchip.AddSuperchip()
}
return nil
}
// fingerprinting a PlusROM cartridge is slightly different to the main
// fingerprint() function above. the fingerprintPlusROM() function below is the
// first step. it checks for the byte sequence 8d f1 x1, which is the
// equivalent to STA $xff1, a necessary instruction in a PlusROM cartridge
//
// if this sequence is found then the function returns true, whereupon
// plusrom.NewPlusROM() can be called. the seoncd part of the fingerprinting
// process occurs in that function. if that fails then we can say that the true
// result from this function was a false positive.
func (cart *Cartridge) fingerprintPlusROM(cartload cartridgeloader.Loader) bool {
for i := 0; i < len(cartload.Data)-2; i++ {
if cartload.Data[i] == 0x8d && cartload.Data[i+1] == 0xf1 && (cartload.Data[i+2]&0x10) == 0x10 {
return true
}
}
return false
}