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This commit is contained in:
Thomas Harte 2024-12-07 11:54:55 -06:00
parent 0d52cf5f97
commit 84ea04f61d
2 changed files with 15 additions and 18 deletions
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31
Storage/Disk/DiskImage/Formats/D64.cpp
View File

@ -19,8 +19,8 @@ using namespace Storage::Disk;
D64::D64(const std::string &file_name) :
file_(file_name) {
// In D64, this is it for validation without imposing potential false-negative tests: check that
// the file size appears to be correct. Stone-age stuff.
// In D64, this is it for validation without imposing potential false-negative tests:
// check that the file size appears to be correct. Stone-age stuff.
if(file_.stats().st_size != 174848 && file_.stats().st_size != 196608)
throw Error::InvalidFormat;
@ -28,7 +28,6 @@ D64::D64(const std::string &file_name) :
// Then, ostensibly, this is a valid file. Pick a disk ID as a
// function of the file_name, being the most stable thing available.
disk_id_ = 0;
for(const auto &character: file_name) {
disk_id_ ^= character;
disk_id_ = uint16_t((disk_id_ << 2) ^ (disk_id_ >> 13));
@ -39,8 +38,8 @@ HeadPosition D64::get_maximum_head_position() {
return HeadPosition(number_of_tracks_);
}
std::shared_ptr<Track> D64::get_track_at_position(Track::Address address) {
// figure out where this track starts on the disk
std::shared_ptr<Track> D64::get_track_at_position(const Track::Address address) {
// Figure out where this track starts on the disk.
int offset_to_track = 0;
int tracks_to_traverse = address.position.as_int();
@ -54,12 +53,12 @@ std::shared_ptr<Track> D64::get_track_at_position(Track::Address address) {
if(tracks_in_this_zone == zone_sizes[current_zone]) zone++;
}
// seek to start of data
// Seek to start of data.
file_.seek(offset_to_track * 256, SEEK_SET);
// build up a PCM sampling of the GCR version of this track
// Build up a PCM sampling of the GCR version of this track.
// format per sector:
// Format per sector:
//
// syncronisation: three $FFs directly in GCR
// value $08 to announce a header
@ -86,39 +85,39 @@ std::shared_ptr<Track> D64::get_track_at_position(Track::Address address) {
uint8_t *sector_data = &data[size_t(sector) * 349];
sector_data[0] = sector_data[1] = sector_data[2] = 0xff;
uint8_t sector_number = uint8_t(sector); // sectors count from 0
uint8_t track_number = uint8_t(address.position.as_int() + 1); // tracks count from 1
uint8_t sector_number = uint8_t(sector); // Sectors count from 0.
uint8_t track_number = uint8_t(address.position.as_int() + 1); // Tracks count from 1.
uint8_t checksum = uint8_t(sector_number ^ track_number ^ disk_id_ ^ (disk_id_ >> 8));
uint8_t header_start[4] = {
0x08, checksum, sector_number, track_number
};
Encodings::CommodoreGCR::encode_block(&sector_data[3], header_start);
uint8_t header_end[4] = {
const uint8_t header_end[4] = {
uint8_t(disk_id_ & 0xff), uint8_t(disk_id_ >> 8), 0, 0
};
Encodings::CommodoreGCR::encode_block(&sector_data[8], header_end);
// pad out post-header parts
// Pad out post-header parts.
uint8_t zeros[4] = {0, 0, 0, 0};
Encodings::CommodoreGCR::encode_block(&sector_data[13], zeros);
sector_data[18] = 0x52;
sector_data[19] = 0x94;
sector_data[20] = 0xaf;
// get the actual contents
// Get the actual contents.
uint8_t source_data[256];
file_.read(source_data, sizeof(source_data));
// compute the latest checksum
// Compute the latest checksum.
checksum = 0;
for(int c = 0; c < 256; c++)
checksum ^= source_data[c];
// put in another sync
// Put in another sync.
sector_data[21] = sector_data[22] = sector_data[23] = 0xff;
// now start writing in the actual data
// Now start writing in the actual data.
uint8_t start_of_data[4] = {
0x07, source_data[0], source_data[1], source_data[2]
};

2
Storage/Disk/DiskImage/Formats/D64.hpp
View File

@ -26,9 +26,7 @@ public:
*/
D64(const std::string &file_name);
// implemented to satisfy @c Disk
HeadPosition get_maximum_head_position() final;
using DiskImage::get_is_read_only;
std::shared_ptr<Track> get_track_at_position(Track::Address address) final;
private: