Zorchenhimer
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go-studybox
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Some cleanup an the decode code 

Added a bunch of comments and clarified some variables in the decoding
logic.
This commit is contained in:
Zorchenhimer 2024-09-29 15:00:44 -04:00
parent 928a8e2faf
commit 3d5790e230
Signed by: Zorchenhimer
GPG Key ID: 70A1AB767AAB9C20
3 changed files with 29 additions and 18 deletions
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24
rom/decoder.go
View File

@ -10,17 +10,18 @@ import (
// Returns packet, next state, and error (if any)
type decodeFunction func(page *Page, data []byte, startIdx int) (Packet, int, error)
// map of states. each state is a map of types
// Map of states. Each state is a map of types
var definedPackets = map[int]map[byte]decodeFunction{
0: map[byte]decodeFunction{
0: map[byte]decodeFunction{ // state 3 in firmware.org
0x01: decodeHeader,
},
1: map[byte]decodeFunction{
1: map[byte]decodeFunction{ // state 1 in firmware.org
0x00: decodeMarkDataEnd,
},
2: map[byte]decodeFunction{
2: map[byte]decodeFunction{ // state 2 in firmware.org
0x02: decodeSetWorkRamLoad,
0x03: decodeMarkDataStart,
0x04: decodeMarkDataStart,
@ -45,18 +46,19 @@ func (page *Page) decode(data []byte) error {
return nil
}
stateArg := data[idx+1]
var packet Packet
if page.state == 1 && data[idx+1] != 0x00 {
if page.state == 1 && stateArg != 0x00 { // stateArg is length here?
// bulk data
packet, page.state, err = decodeBulkData(page, data, idx)
if err != nil {
return err
}
} else {
df, ok := definedPackets[page.state][data[idx+1]]
df, ok := definedPackets[page.state][stateArg]
if !ok {
return fmt.Errorf("State %d packet with type %02X isn't implemented",
page.state, data[idx+1])
page.state, stateArg)
}
packet, page.state, err = df(page, data, idx)
if err != nil {
@ -149,7 +151,7 @@ func decodeMarkDataStart(page *Page, data []byte, idx int) (Packet, int, error)
func decodeMarkDataEnd(page *Page, data []byte, idx int) (Packet, int, error) {
packet := &packetMarkDataEnd{
Type: data[idx+2],
Reset: (data[idx+2]&0xF0 == 0xF0),
Reset: (data[idx+2]&0xF0 == 0xF0), // what is this?
checksum: data[idx+3],
address: page.DataOffset + idx,
}
@ -195,6 +197,9 @@ func decodeSetWorkRamLoad(page *Page, data []byte, idx int) (Packet, int, error)
}
func decodeBulkData(page *Page, data []byte, idx int) (Packet, int, error) {
// idx+1: length of data
// idx+2: data start
if data[idx+1] == 0 {
return nil, 0, fmt.Errorf("Bulk data packet has a length of zero at offset %08X",
page.DataOffset+idx)
@ -206,8 +211,9 @@ func decodeBulkData(page *Page, data []byte, idx int) (Packet, int, error) {
datalen := int(data[idx+1])
packet.Data = data[idx+2 : idx+2+datalen]
packet.checksum = data[idx+len(packet.Data)+2]
packet.checksum = data[idx+2+len(packet.Data)]
// checksum includes the packet ID and data length values
checksum := calcChecksum(data[idx : idx+int(data[idx+1])+2])
if checksum != packet.checksum {
data := []string{}

14
rom/export.go
View File

@ -13,6 +13,10 @@ func (sb *StudyBox) Export(directory string) error {
Audio: directory + "/audio" + sb.Audio.ext(),
}
// A "Page" here does not correspond to the entered "Page" number on the
// title screen. These are really segments. The "Page" that is entered on
// the title screen is stored in the header of a segment. Multiple
// segments can have the same "Page" number.
for pidx, page := range sb.Data.Pages {
jp := jsonPage{
AudioOffsetLeadIn: page.AudioOffsetLeadIn,
@ -20,7 +24,7 @@ func (sb *StudyBox) Export(directory string) error {
Data: []jsonData{},
}
file, err := os.Create(fmt.Sprintf("%s/page%02d_0000.txt", directory, pidx))
file, err := os.Create(fmt.Sprintf("%s/segment-%02d_packet-0000.txt", directory, pidx))
if err != nil {
return err
}
@ -74,13 +78,13 @@ func (sb *StudyBox) Export(directory string) error {
switch jData.Type {
case "pattern":
jData.File = fmt.Sprintf("%s/page%02d_%04d_chrData.chr", directory, pidx, dataStartId)
jData.File = fmt.Sprintf("%s/segment-%02d_packet-%04d_chrData.chr", directory, pidx, dataStartId)
case "nametable":
jData.File = fmt.Sprintf("%s/page%02d_%04d_ntData.dat", directory, pidx, dataStartId)
jData.File = fmt.Sprintf("%s/segment-%02d_packet-%04d_ntData.dat", directory, pidx, dataStartId)
case "script":
jData.File = fmt.Sprintf("%s/page%02d_%04d_scriptData.dat", directory, pidx, dataStartId)
jData.File = fmt.Sprintf("%s/segment-%02d_packet-%04d_scriptData.dat", directory, pidx, dataStartId)
//script, err := DissassembleScript(scriptData)
//if err != nil {
@ -118,7 +122,7 @@ func (sb *StudyBox) Export(directory string) error {
rawData = append(rawData, p.Data...)
default:
return fmt.Errorf("Encountered an unknown packet: %s page: %d", p.Asm(), pidx)
return fmt.Errorf("Encountered an unknown packet: %s segment: %d", p.Asm(), pidx)
}
}

9
rom/packets.go
View File

@ -26,7 +26,7 @@ func (ph *packetHeader) RawBytes() []byte {
}
func (ph *packetHeader) Asm() string {
return fmt.Sprintf("header %d ; Checksum: %02X", ph.PageNumber, ph.Checksum)
return fmt.Sprintf("header %d [Page %d] ; Checksum: %02X", ph.PageNumber, ph.PageNumber+1, ph.Checksum)
}
func (ph *packetHeader) Address() int {
@ -81,7 +81,7 @@ func newPacketWorkRamLoad(bank, addressHigh uint8) *packetWorkRamLoad {
}
func (p *packetWorkRamLoad) Asm() string {
return fmt.Sprintf("work_ram_load $%02X $%02X ; Checksum %02X",
return fmt.Sprintf("work_ram_load bank:$%02X addr:$%02X00 ; Checksum %02X",
p.bankId, p.loadAddressHigh, p.checksum)
}
@ -192,7 +192,7 @@ func (p *packetMarkDataStart) Address() int {
type packetMarkDataEnd struct {
//Arg uint8
Reset bool
Reset bool // what does this mean? what is special about the value 0xF0?
Type uint8
address int
@ -251,7 +251,8 @@ func (p *packetMarkDataEnd) Asm() string {
for _, b := range p.RawBytes() {
s = append(s, fmt.Sprintf("%02X", b))
}
return fmt.Sprintf("mark_datatype_end %s ; %s Checksum: %02X", tstr, strings.Join(s, " "), p.checksum)
return fmt.Sprintf("mark_datatype_end %s ; %s Checksum: %02X",
tstr, strings.Join(s, " "), p.checksum)
}
func (p *packetMarkDataEnd) Address() int {