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Merge pull request #490 from TomHarte/NIBTails

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Ensures NIB tracks aren't truncated
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Thomas Harte 2018-07-03 21:38:31 -04:00 committed by GitHub
commit fa63f7ffc3
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1 changed files with 35 additions and 8 deletions
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43
Storage/Disk/DiskImage/Formats/NIB.cpp
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@ -75,7 +75,9 @@ std::shared_ptr<::Storage::Disk::Track> NIB::get_track_at_position(::Storage::Di
// Establish where syncs start by finding instances of 0xd5 0xaa and then regressing
// from each along all preceding FFs.
for(size_t index = 0; index < track_data.size(); ++index) {
// This is a D5 AA...
if(track_data[index] == 0xd5 && track_data[(index+1)%track_data.size()] == 0xaa) {
// ... count backwards to find out where the preceding FFs started.
size_t start = index - 1;
size_t length = 0;
while(track_data[start] == 0xff && length < 5) {
@ -83,8 +85,13 @@ std::shared_ptr<::Storage::Disk::Track> NIB::get_track_at_position(::Storage::Di
++length;
}
// Record a sync position only if there were at least five FFs.
if(length == 5) {
sync_starts.insert((start + 1) % track_data.size());
// If the apparent start of this sync area is 'after' the start, then
// this sync period overlaps position zero. So this track will start
// in a sync block.
if(start > index)
start_index = start;
}
@ -92,25 +99,36 @@ std::shared_ptr<::Storage::Disk::Track> NIB::get_track_at_position(::Storage::Di
}
PCMSegment segment;
// If the track started in a sync block, write sync first.
if(start_index) {
segment += Encodings::AppleGCR::six_and_two_sync(static_cast<int>(start_index));
}
std::size_t index = start_index;
for(const auto &location: sync_starts) {
// Write from index to sync_start.
for(const auto location: sync_starts) {
// Write data from index to sync_start.
std::vector<uint8_t> data_segment(
track_data.begin() + static_cast<off_t>(index),
track_data.begin() + static_cast<off_t>(location));
segment += PCMSegment(data_segment);
// Add a sync from sync_start to end of 0xffs.
if(location == track_length-1) break;
// Add a sync from sync_start to end of 0xffs, if there are
// any before the end of data.
index = location;
while(index < track_length && track_data[index] == 0xff)
++index;
segment += Encodings::AppleGCR::six_and_two_sync(static_cast<int>(index - location));
if(index - location)
segment += Encodings::AppleGCR::six_and_two_sync(static_cast<int>(index - location));
}
// If there's still data remaining on the track, write it out.
if(index < track_length) {
std::vector<uint8_t> data_segment(
track_data.begin() + static_cast<off_t>(index),
track_data.end());
segment += PCMSegment(data_segment);
}
return std::make_shared<PCMTrack>(segment);
@ -129,20 +147,29 @@ void NIB::set_tracks(const std::map<Track::Address, std::shared_ptr<Track>> &tra
std::vector<uint8_t> track;
track.reserve(track_length);
uint8_t shifter = 0;
int bit_count = 0;
size_t sync_location = 0, location = 0;
for(const auto bit: segment.data) {
shifter = static_cast<uint8_t>((shifter << 1) | (bit ? 1 : 0));
++bit_count;
++location;
if(shifter & 0x80) {
track.push_back(shifter);
if(bit_count == 10) {
sync_location = location;
}
shifter = 0;
bit_count = 0;
}
}
// Pad out to track_length.
// Trim or pad out to track_length.
if(track.size() > track_length) {
track.resize(track_length);
} else {
while(track.size() < track_length) {
track.push_back(0xff);
std::vector<uint8_t> extra_data(static_cast<size_t>(track_length) - track.size(), 0xff);
track.insert(track.begin() + static_cast<off_t>(sync_location), extra_data.begin(), extra_data.end());
}
}