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mapper_parkerbros.go
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mapper_parkerbros.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 (
"fmt"
"math/rand"
"github.com/jetsetilly/gopher2600/curated"
"github.com/jetsetilly/gopher2600/hardware/memory/bus"
"github.com/jetsetilly/gopher2600/hardware/memory/cartridge/mapper"
"github.com/jetsetilly/gopher2600/hardware/memory/memorymap"
)
// from bankswitch_sizes.txt:
//
// -E0: Parker Brothers was the main user of this method. This cart is
// segmented into 4 1K segments. Each segment can point to one 1K slice of the
// ROM image. You select the desired 1K slice by accessing 1FE0 to 1FE7 for
// the first 1K (1FE0 selects slice 0, 1FE1 selects slice 1, etc). 1FE8 to
// 1FEF selects the slice for the second 1K, and 1FF0 to 1FF8 selects the slice
// for the third 1K. The last 1K always points to the last 1K of the ROM image
// so that the cart always starts up in the exact same place.
//
//
// cartridges:
// - Montezuma's Revenge
// - Lord of the Rings
// - etc.
type parkerBros struct {
mappingID string
description string
// parkerBros cartridges have 8 banks of 1024 bytes
bankSize int
banks [][]uint8
// rewindable state
state *parkerBrosState
}
func newParkerBros(data []byte) (mapper.CartMapper, error) {
cart := &parkerBros{
mappingID: "E0",
description: "parker bros",
bankSize: 1024,
state: newParkerBrosState(),
}
cart.banks = make([][]uint8, cart.NumBanks())
if len(data) != cart.bankSize*cart.NumBanks() {
return nil, curated.Errorf("E0: %v", "wrong number of bytes in the cartridge data")
}
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])
}
return cart, nil
}
// Mapping implements the mapper.CartMapper interface.
func (cart *parkerBros) Mapping() string {
return fmt.Sprintf("Banks: %d %d %d %d", cart.state.segment[0], cart.state.segment[1], cart.state.segment[2], cart.state.segment[3])
}
// ID implements the mapper.CartMapper interface.
func (cart *parkerBros) ID() string {
return cart.mappingID
}
// Snapshot implements the mapper.CartMapper interface.
func (cart *parkerBros) Snapshot() mapper.CartMapper {
n := *cart
n.state = cart.state.Snapshot()
return &n
}
// Plumb implements the mapper.CartMapper interface.
func (cart *parkerBros) Plumb() {
}
// Reset implements the mapper.CartMapper interface.
func (cart *parkerBros) Reset(randSrc *rand.Rand) {
cart.state.segment[0] = cart.NumBanks() - 4
cart.state.segment[1] = cart.NumBanks() - 3
cart.state.segment[2] = cart.NumBanks() - 2
cart.state.segment[3] = cart.NumBanks() - 1
}
// Read implements the mapper.CartMapper interface.
func (cart *parkerBros) Read(addr uint16, passive bool) (uint8, error) {
var data uint8
if addr >= 0x0000 && addr <= 0x03ff {
data = cart.banks[cart.state.segment[0]][addr&0x03ff]
} else if addr >= 0x0400 && addr <= 0x07ff {
data = cart.banks[cart.state.segment[1]][addr&0x03ff]
} else if addr >= 0x0800 && addr <= 0x0bff {
data = cart.banks[cart.state.segment[2]][addr&0x03ff]
} else if addr >= 0x0c00 && addr <= 0x0fff {
data = cart.banks[cart.state.segment[3]][addr&0x03ff]
}
cart.bankswitch(addr, passive)
return data, nil
}
// Write implements the mapper.CartMapper interface.
func (cart *parkerBros) Write(addr uint16, data uint8, passive bool, poke bool) error {
if poke {
if addr >= 0x0000 && addr <= 0x03ff {
cart.banks[cart.state.segment[0]][addr&0x3ff] = data
} else if addr >= 0x0400 && addr <= 0x07ff {
cart.banks[cart.state.segment[1]][addr&0x3ff] = data
} else if addr >= 0x0800 && addr <= 0x0bff {
cart.banks[cart.state.segment[2]][addr&0x3ff] = data
} else if addr >= 0x0c00 && addr <= 0x0fff {
cart.banks[cart.state.segment[3]][addr&0x3ff] = data
}
}
cart.bankswitch(addr, passive)
return curated.Errorf("E0: %v", curated.Errorf(bus.AddressError, addr))
}
// bankswitch on hotspot access.
func (cart *parkerBros) bankswitch(addr uint16, passive bool) {
if addr >= 0xfe0 && addr <= 0xff7 {
if passive {
return
}
switch addr {
// segment 0
case 0x0fe0:
cart.state.segment[0] = 0
case 0x0fe1:
cart.state.segment[0] = 1
case 0x0fe2:
cart.state.segment[0] = 2
case 0x0fe3:
cart.state.segment[0] = 3
case 0x0fe4:
cart.state.segment[0] = 4
case 0x0fe5:
cart.state.segment[0] = 5
case 0x0fe6:
cart.state.segment[0] = 6
case 0x0fe7:
cart.state.segment[0] = 7
// segment 1
case 0x0fe8:
cart.state.segment[1] = 0
case 0x0fe9:
cart.state.segment[1] = 1
case 0x0fea:
cart.state.segment[1] = 2
case 0x0feb:
cart.state.segment[1] = 3
case 0x0fec:
cart.state.segment[1] = 4
case 0x0fed:
cart.state.segment[1] = 5
case 0x0fee:
cart.state.segment[1] = 6
case 0x0fef:
cart.state.segment[1] = 7
// segment 2
case 0x0ff0:
cart.state.segment[2] = 0
case 0x0ff1:
cart.state.segment[2] = 1
case 0x0ff2:
cart.state.segment[2] = 2
case 0x0ff3:
cart.state.segment[2] = 3
case 0x0ff4:
cart.state.segment[2] = 4
case 0x0ff5:
cart.state.segment[2] = 5
case 0x0ff6:
cart.state.segment[2] = 6
case 0x0ff7:
cart.state.segment[2] = 7
}
}
}
// NumBanks implements the mapper.CartMapper interface.
func (cart *parkerBros) NumBanks() int {
return 8
}
// GetBank implements the mapper.CartMapper interface.
func (cart *parkerBros) GetBank(addr uint16) mapper.BankInfo {
var seg int
if addr >= 0x0000 && addr <= 0x03ff {
seg = 0
} else if addr >= 0x0400 && addr <= 0x07ff {
seg = 1
} else if addr >= 0x0800 && addr <= 0x0bff {
seg = 2
} else { // remaining address is between 0x0c00 and 0x0fff
seg = 3
}
return mapper.BankInfo{Number: cart.state.segment[seg], IsRAM: false, IsSegmented: true, Segment: seg}
}
// Patch implements the mapper.CartMapper interface.
func (cart *parkerBros) Patch(offset int, data uint8) error {
if offset >= cart.bankSize*len(cart.banks) {
return curated.Errorf("E0: %v", fmt.Errorf("patch offset too high (%v)", offset))
}
bank := offset / cart.bankSize
offset %= cart.bankSize
cart.banks[bank][offset] = data
return nil
}
// Listen implements the mapper.CartMapper interface.
func (cart *parkerBros) Listen(_ uint16, _ uint8) {
}
// Step implements the mapper.CartMapper interface.
func (cart *parkerBros) Step(_ float32) {
}
// IterateBank implements the mapper.CartMapper interface.
func (cart *parkerBros) CopyBanks() []mapper.BankContent {
c := make([]mapper.BankContent, len(cart.banks))
// banks 0 to len-1 can occupy any of the three segments
for b := 0; b < len(cart.banks)-1; b++ {
c[b] = mapper.BankContent{Number: b,
Data: cart.banks[b],
Origins: []uint16{
memorymap.OriginCart,
memorymap.OriginCart + uint16(cart.bankSize),
memorymap.OriginCart + uint16(cart.bankSize)*2,
},
}
}
// last bank can occupy any of the four segments (the last segment always
// points to bank 7 but bank 7 can also be in another segment at the
// same time)
b := len(cart.banks) - 1
c[b] = mapper.BankContent{Number: b,
Data: cart.banks[b],
Origins: []uint16{
memorymap.OriginCart,
memorymap.OriginCart + uint16(cart.bankSize),
memorymap.OriginCart + uint16(cart.bankSize)*2,
memorymap.OriginCart + uint16(cart.bankSize)*3,
},
}
return c
}
// ReadHotspots implements the mapper.CartHotspotsBus interface.
func (cart *parkerBros) ReadHotspots() map[uint16]mapper.CartHotspotInfo {
return map[uint16]mapper.CartHotspotInfo{
// segment 0
0x0fe0: {Symbol: "B0S0", Action: mapper.HotspotBankSwitch},
0x0fe1: {Symbol: "B1S0", Action: mapper.HotspotBankSwitch},
0x0fe2: {Symbol: "B2S0", Action: mapper.HotspotBankSwitch},
0x0fe3: {Symbol: "B3S0", Action: mapper.HotspotBankSwitch},
0x0fe4: {Symbol: "B4S0", Action: mapper.HotspotBankSwitch},
0x0fe5: {Symbol: "B5S0", Action: mapper.HotspotBankSwitch},
0x0fe6: {Symbol: "B6S0", Action: mapper.HotspotBankSwitch},
0x0fe7: {Symbol: "B7S0", Action: mapper.HotspotBankSwitch},
// segment 1
0x0fe8: {Symbol: "B0S1", Action: mapper.HotspotBankSwitch},
0x0fe9: {Symbol: "B1S1", Action: mapper.HotspotBankSwitch},
0x0fea: {Symbol: "B2S1", Action: mapper.HotspotBankSwitch},
0x0feb: {Symbol: "B3S1", Action: mapper.HotspotBankSwitch},
0x0fec: {Symbol: "B4S1", Action: mapper.HotspotBankSwitch},
0x0fed: {Symbol: "B5S1", Action: mapper.HotspotBankSwitch},
0x0fee: {Symbol: "B6S1", Action: mapper.HotspotBankSwitch},
0x0fef: {Symbol: "B7S1", Action: mapper.HotspotBankSwitch},
// segment 2
0x0ff0: {Symbol: "B0S2", Action: mapper.HotspotBankSwitch},
0x0ff1: {Symbol: "B1S2", Action: mapper.HotspotBankSwitch},
0x0ff2: {Symbol: "B2S2", Action: mapper.HotspotBankSwitch},
0x0ff3: {Symbol: "B3S2", Action: mapper.HotspotBankSwitch},
0x0ff4: {Symbol: "B4S2", Action: mapper.HotspotBankSwitch},
0x0ff5: {Symbol: "B5S2", Action: mapper.HotspotBankSwitch},
0x0ff6: {Symbol: "B6S2", Action: mapper.HotspotBankSwitch},
0x0ff7: {Symbol: "B7S2", Action: mapper.HotspotBankSwitch},
}
}
// WriteHotspots implements the mapper.CartHotspotsBus interface.
func (cart *parkerBros) WriteHotspots() map[uint16]mapper.CartHotspotInfo {
return cart.ReadHotspots()
}
// rewindable state for the parker bros. cartridges.
type parkerBrosState struct {
// parkerBros cartridges divide memory into 4 segments
// o the last segment always points to the last bank
// o the other segments can point to any one of the eight banks in the ROM
// (including the last bank)
segment [4]int
}
func newParkerBrosState() *parkerBrosState {
return &parkerBrosState{}
}
// Snapshot implements the mapper.CartMapper interface.
func (s *parkerBrosState) Snapshot() *parkerBrosState {
n := *s
return &n
}