mirror of
https://github.com/giongto35/cloud-game.git
synced 2026-07-22 09:37:09 +00:00
70 lines
1.5 KiB
Go
70 lines
1.5 KiB
Go
package nes
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import (
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"encoding/gob"
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"log"
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)
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type Mapper3 struct {
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*Cartridge
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chrBank int
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prgBank1 int
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prgBank2 int
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}
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func NewMapper3(cartridge *Cartridge) Mapper {
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prgBanks := len(cartridge.PRG) / 0x4000
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return &Mapper3{cartridge, 0, 0, prgBanks - 1}
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}
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func (m *Mapper3) Save(encoder *gob.Encoder) error {
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encoder.Encode(m.chrBank)
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encoder.Encode(m.prgBank1)
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encoder.Encode(m.prgBank2)
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return nil
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}
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func (m *Mapper3) Load(decoder *gob.Decoder) error {
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decoder.Decode(&m.chrBank)
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decoder.Decode(&m.prgBank1)
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decoder.Decode(&m.prgBank2)
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return nil
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}
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func (m *Mapper3) Step() {
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}
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func (m *Mapper3) Read(address uint16) byte {
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switch {
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case address < 0x2000:
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index := m.chrBank*0x2000 + int(address)
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return m.CHR[index]
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case address >= 0xC000:
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index := m.prgBank2*0x4000 + int(address-0xC000)
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return m.PRG[index]
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case address >= 0x8000:
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index := m.prgBank1*0x4000 + int(address-0x8000)
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return m.PRG[index]
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case address >= 0x6000:
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index := int(address) - 0x6000
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return m.SRAM[index]
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default:
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log.Fatalf("unhandled mapper3 read at address: 0x%04X", address)
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}
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return 0
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}
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func (m *Mapper3) Write(address uint16, value byte) {
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switch {
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case address < 0x2000:
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index := m.chrBank*0x2000 + int(address)
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m.CHR[index] = value
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case address >= 0x8000:
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m.chrBank = int(value & 3)
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case address >= 0x6000:
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index := int(address) - 0x6000
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m.SRAM[index] = value
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default:
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log.Fatalf("unhandled mapper3 write at address: 0x%04X", address)
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}
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}
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