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Introduces support for writing NIBs.

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This commit is contained in:
Thomas Harte 2018-05-25 18:30:55 -04:00
parent 79c60b8984
commit f443fd44b5
2 changed files with 63 additions and 7 deletions
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60
Storage/Disk/DiskImage/Formats/NIB.cpp
View File

@ -9,6 +9,7 @@
#include "NIB.hpp"
#include "../../Track/PCMTrack.hpp"
#include "../../Track/TrackSerialiser.hpp"
#include "../../Encodings/AppleGCR/Encoder.hpp"
#include <vector>
@ -36,13 +37,25 @@ HeadPosition NIB::get_maximum_head_position() {
return HeadPosition(number_of_tracks);
}
bool NIB::get_is_read_only() {
return file_.get_is_known_read_only();
}
long NIB::file_offset(Track::Address address) {
return static_cast<long>(address.position.as_int()) * track_length;
}
std::shared_ptr<::Storage::Disk::Track> NIB::get_track_at_position(::Storage::Disk::Track::Address address) {
// NIBs contain data for even-numbered tracks underneath a single head only.
if(address.head) return nullptr;
const long file_track = static_cast<long>(address.position.as_int());
file_.seek(file_track * track_length, SEEK_SET);
std::vector<uint8_t> track_data = file_.read(track_length);
long offset = file_offset(address);
std::vector<uint8_t> track_data;
{
std::lock_guard<std::mutex> lock_guard(file_.get_file_access_mutex());
file_.seek(offset, SEEK_SET);
track_data = file_.read(track_length);
}
// NIB files leave sync bytes implicit and make no guarantees
// about overall track positioning. So the approach taken here
@ -100,3 +113,44 @@ std::shared_ptr<::Storage::Disk::Track> NIB::get_track_at_position(::Storage::Di
return std::make_shared<PCMTrack>(segment);
}
void NIB::set_tracks(const std::map<Track::Address, std::shared_ptr<Track>> &tracks) {
std::map<Track::Address, std::vector<uint8_t>> tracks_by_address;
// Convert to a map from address to a vector of data that contains the NIB representation
// of the track.
for(const auto &pair: tracks) {
// Grab the track bit stream.
auto segment = Storage::Disk::track_serialisation(*pair.second, Storage::Time(1, 50000));
// Process to eliminate all sync bits.
std::vector<uint8_t> track;
track.reserve(track_length);
uint8_t shifter = 0;
for(unsigned int bit = 0; bit < segment.number_of_bits; ++bit) {
shifter = static_cast<uint8_t>((shifter << 1) | segment.bit(bit));
if(shifter & 0x80) {
track.push_back(shifter);
shifter = 0;
}
}
// Pad out to track_length.
if(track.size() > track_length) {
track.resize(track_length);
} else {
while(track.size() < track_length) {
track.push_back(0xff);
}
}
tracks_by_address[pair.first] = std::move(track);
}
// Lock the file and spool out.
std::lock_guard<std::mutex> lock_guard(file_.get_file_access_mutex());
for(const auto &track: tracks_by_address) {
file_.seek(file_offset(track.first), SEEK_SET);
file_.write(track.second);
}
}

10
Storage/Disk/DiskImage/Formats/NIB.hpp
View File

@ -17,21 +17,23 @@ namespace Disk {
/*!
Provides a @c DiskImage describing an Apple NIB disk image:
mostly a bit stream capture, but syncs are implicitly packed
into 8 bits instead of 9.
a bit stream capture that omits sync zeroes, and doesn't define
the means for full reconstruction.
*/
class NIB: public DiskImage {
public:
NIB(const std::string &file_name);
// Implemented to satisfy @c DiskImage.
HeadPosition get_maximum_head_position() override;
std::shared_ptr<::Storage::Disk::Track> get_track_at_position(::Storage::Disk::Track::Address address) override;
void set_tracks(const std::map<Track::Address, std::shared_ptr<Track>> &tracks) override;
bool get_is_read_only() override;
private:
FileHolder file_;
long get_file_offset_for_position(Track::Address address);
long file_offset(Track::Address address);
};
}