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Factors out physical to logical sector conversion.

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This commit is contained in:
Thomas Harte 2018-05-19 22:59:59 -04:00
parent 46fae1a761
commit 4952657b31
2 changed files with 11 additions and 12 deletions
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20
Storage/Disk/DiskImage/Formats/AppleDSK.cpp
View File

@ -52,6 +52,13 @@ long AppleDSK::file_offset(Track::Address address) {
return address.position.as_int() * bytes_per_sector * sectors_per_track_;
}
size_t AppleDSK::logical_sector_for_physical_sector(size_t physical) {
// DOS and Pro DOS interleave sectors on disk, and they're represented in a disk
// image in physical order rather than logical.
if(physical == 15) return 15;
return (physical * (is_prodos_ ? 8 : 7)) % 15;
}
std::shared_ptr<Track> AppleDSK::get_track_at_position(Track::Address address) {
std::vector<uint8_t> track_data;
{
@ -66,17 +73,11 @@ std::shared_ptr<Track> AppleDSK::get_track_at_position(Track::Address address) {
// In either case below, the code aims for exactly 50,000 bits per track.
if(sectors_per_track_ == 16) {
// Write the sectors.
std::size_t sector_number_ = 0;
for(uint8_t c = 0; c < 16; ++c) {
segment += Encodings::AppleGCR::six_and_two_sync(10);
segment += Encodings::AppleGCR::header(254, track, c);
segment += Encodings::AppleGCR::six_and_two_sync(10);
segment += Encodings::AppleGCR::six_and_two_data(&track_data[sector_number_ * 256]);
// DOS and Pro DOS interleave sectors on disk, and they're represented in a disk
// image in physical order rather than logical. So that skew needs to be applied here.
sector_number_ += is_prodos_ ? 8 : 7;
if(sector_number_ > 0xf) sector_number_ %= 15;
segment += Encodings::AppleGCR::six_and_two_data(&track_data[logical_sector_for_physical_sector(c) * 256]);
}
// Pad if necessary.
@ -100,10 +101,7 @@ void AppleDSK::set_tracks(const std::map<Track::Address, std::shared_ptr<Track>>
// Rearrange sectors into Apple DOS or Pro-DOS order.
std::vector<uint8_t> track_contents(static_cast<size_t>(bytes_per_sector * sectors_per_track_));
for(const auto &sector_pair: sector_map) {
size_t target_address = sector_pair.second.address.sector;
if(target_address != 15) {
target_address = (target_address * (is_prodos_ ? 8 : 7)) % 15;
}
const size_t target_address = logical_sector_for_physical_sector(sector_pair.second.address.sector);
memcpy(&track_contents[target_address*256], sector_pair.second.data.data(), bytes_per_sector);
}

3
Storage/Disk/DiskImage/Formats/AppleDSK.hpp
View File

@ -31,7 +31,7 @@ class AppleDSK: public DiskImage {
*/
AppleDSK(const std::string &file_name);
// implemented to satisfy @c Disk
// Implemented to satisfy @c Disk.
HeadPosition get_maximum_head_position() override;
std::shared_ptr<Track> get_track_at_position(Track::Address address) override;
void set_tracks(const std::map<Track::Address, std::shared_ptr<Track>> &tracks) override;
@ -43,6 +43,7 @@ class AppleDSK: public DiskImage {
bool is_prodos_ = false;
long file_offset(Track::Address address);
size_t logical_sector_for_physical_sector(size_t physical);
};
}