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mapper_ua.go
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/
mapper_ua.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 (
"crypto/sha1"
"fmt"
"io"
"github.com/jetsetilly/gopher2600/cartridgeloader"
"github.com/jetsetilly/gopher2600/environment"
"github.com/jetsetilly/gopher2600/hardware/memory/cartridge/mapper"
"github.com/jetsetilly/gopher2600/hardware/memory/memorymap"
"github.com/jetsetilly/gopher2600/logger"
)
type ua struct {
env *environment.Environment
mappingID string
// ua cartridges are 8k in size and have two banks of 4096 bytes
bankSize int
banks [][]uint8
// identifies the currently selected bank
bank int
// the hotspot addresses are swapped
swappedHotspots bool
}
func newUA(env *environment.Environment, loader cartridgeloader.Loader) (mapper.CartMapper, error) {
data, err := io.ReadAll(loader)
if err != nil {
return nil, fmt.Errorf("UA: %w", err)
}
cart := &ua{
env: env,
mappingID: "UA",
bankSize: 4096,
swappedHotspots: false,
}
if len(data) != cart.bankSize*cart.NumBanks() {
return nil, fmt.Errorf("UA: wrong number of bytes in the cartridge data")
}
cart.banks = make([][]uint8, cart.NumBanks())
for k := 0; k < cart.NumBanks(); k++ {
cart.banks[k] = make([]uint8, cart.bankSize)
offset := k * cart.bankSize
copy(cart.banks[k], data[offset:offset+cart.bankSize])
}
// only one cartridge dump is known to have swapped hotspots
if fmt.Sprintf("%0x", sha1.Sum(data)) == "6d4a94c2348bbd8e9c73b73d8f3389196d42fd54" {
cart.swappedHotspots = true
logger.Logf(env, "UA", "swapping hotspot address for this cartridge (Sorcerer's Apprentice)")
}
return cart, nil
}
// MappedBanks implements the mapper.CartMapper interface
func (cart *ua) MappedBanks() string {
return fmt.Sprintf("Bank: %d", cart.bank)
}
// ID implements the mapper.CartMapper interface
func (cart *ua) ID() string {
return cart.mappingID
}
// Snapshot implements the mapper.CartMapper interface
func (cart *ua) Snapshot() mapper.CartMapper {
n := *cart
return &n
}
// Plumb implements the mapper.CartMapper interface
func (cart *ua) Plumb(env *environment.Environment) {
cart.env = env
}
// Reset implements the mapper.CartMapper interface
func (cart *ua) Reset() {
cart.bank = len(cart.banks) - 1
}
// Access implements the mapper.CartMapper interface
func (cart *ua) Access(addr uint16, _ bool) (uint8, uint8, error) {
return cart.banks[cart.bank][addr], mapper.CartDrivenPins, nil
}
// AccessVolatile implements the mapper.CartMapper interface
func (cart *ua) AccessVolatile(addr uint16, data uint8, poke bool) error {
if poke {
cart.banks[cart.bank][addr] = data
}
return nil
}
// NumBanks implements the mapper.CartMapper interface
func (cart *ua) NumBanks() int {
return 2
}
// GetBank implements the mapper.CartMapper interface
func (cart *ua) GetBank(addr uint16) mapper.BankInfo {
// ua cartridges are like atari cartridges in that the entire address
// space points to the selected bank
return mapper.BankInfo{Number: cart.bank}
}
// AccessPassive implements the mapper.CartMapper interface
func (cart *ua) AccessPassive(addr uint16, data uint8) error {
switch addr & 0x1260 {
case 0x0220:
if cart.swappedHotspots {
cart.bank = 1
} else {
cart.bank = 0
}
case 0x0240:
if cart.swappedHotspots {
cart.bank = 0
} else {
cart.bank = 1
}
}
return nil
}
// Step implements the mapper.CartMapper interface
func (cart *ua) Step(_ float32) {
}
// IterateBank implements the mapper.CartMapper interface
func (cart *ua) CopyBanks() []mapper.BankContent {
c := make([]mapper.BankContent, len(cart.banks))
for b := 0; b < len(cart.banks); b++ {
c[b] = mapper.BankContent{Number: b,
Data: cart.banks[b],
Origins: []uint16{memorymap.OriginCart},
}
}
return c
}
// Patch implements the mapper.CartPatchable interface
func (cart *ua) Patch(offset int, data uint8) error {
if offset >= cart.bankSize*len(cart.banks) {
return fmt.Errorf("UA: patch offset too high (%d)", offset)
}
bank := offset / cart.bankSize
offset %= cart.bankSize
cart.banks[bank][offset] = data
return nil
}