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Ensures no data is dropped in transcribing a NIB to real track data.

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This commit is contained in:
Thomas Harte 2018-07-03 20:01:07 -04:00
parent a391d0f4ae
commit 6e34e60f8a
1 changed files with 24 additions and 6 deletions
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30
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 D% 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);