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Introduces sector interleaving.

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This commit is contained in:
Thomas Harte 2019-07-16 18:05:40 -04:00
parent 3633285aaa
commit 9f0f35033d
1 changed files with 23 additions and 16 deletions
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39
Storage/Disk/DiskImage/Formats/MacintoshIMG.cpp
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@ -27,20 +27,20 @@ MacintoshIMG::MacintoshIMG(const std::string &file_name) :
file_(file_name) {
// Test 1: is this a raw secctor dump? If so it'll start with
// the magic word 0x4C4B (big endian) and be exactly
// 819,200 bytes long if double sided, or 409,600 bytes if
// single sided.
// either the magic word 0x4C4B (big endian) or with 0x00000
// and be exactly 819,200 bytes long if double sided, or
// 409,600 bytes if single sided.
//
// Luckily, 0x4c is an invalid string length for the proper
// Luckily, both 0x00 and 0x4c are invalid string length for the proper
// DiskCopy 4.2 format, so there's no ambiguity here.
const auto name_length = file_.get8();
if(name_length == 0x4c) {
if(name_length == 0x4c || !name_length) {
is_diskCopy_file_ = false;
if(file_.stats().st_size != 819200 && file_.stats().st_size != 409600)
throw Error::InvalidFormat;
uint32_t magic_word = file_.get8();
if(magic_word != 0x4b)
if(!((name_length == 0x4c && magic_word == 0x4b) || (name_length == 0x00 && magic_word == 0x00)))
throw Error::InvalidFormat;
file_.seek(0, SEEK_SET);
@ -165,30 +165,36 @@ std::shared_ptr<::Storage::Disk::Track> MacintoshIMG::get_track_at_position(::St
if(start_sector*512 >= data_.size()) return nullptr;
uint8_t *sector = &data_[512 * start_sector];
uint8_t *tags = tags_.size() ? &tags_[12 * start_sector] : nullptr;
uint8_t *const sector = &data_[512 * start_sector];
uint8_t *const tags = tags_.size() ? &tags_[12 * start_sector] : nullptr;
Storage::Disk::PCMSegment segment;
segment += Encodings::AppleGCR::six_and_two_sync(24);
// Determine the sector ordering.
uint8_t source_sectors[12] = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff, 0xff};
int destination = 0;
for(int c = 0; c < included_sectors.length; ++c) {
// const int interleave_scale = ((format_ & 0x1f) == 4) ? 8 : 4;
uint8_t sector_id = uint8_t(c);//uint8_t((c == included_sectors.length - 1) ? c : (c * interleave_scale)%included_sectors.length);
// Deal with collisions by finding the next non-colliding spot.
while(source_sectors[destination] != 0xff) ++destination;
source_sectors[destination] = uint8_t(c);
destination = (destination + (format_ & 0x1f)) % included_sectors.length;
}
for(int c = 0; c < included_sectors.length; ++c) {
const uint8_t sector_id = source_sectors[c];
uint8_t sector_plus_tags[524];
// Copy in the tags, if provided; otherwise generate them.
if(tags) {
memcpy(sector_plus_tags, tags, 12);
tags += 12;
memcpy(sector_plus_tags, &tags[sector_id * 12], 12);
} else {
// TODO: fill in tags properly.
memset(sector_plus_tags, 0, 12);
}
// Copy in the sector body.
memcpy(&sector_plus_tags[12], sector, 512);
sector += 512;
memcpy(&sector_plus_tags[12], &sector[sector_id * 512], 512);
// NB: sync lengths below are identical to those for
// the Apple II, as I have no idea whatsoever what they
@ -205,8 +211,9 @@ std::shared_ptr<::Storage::Disk::Track> MacintoshIMG::get_track_at_position(::St
segment += Encodings::AppleGCR::six_and_two_sync(20);
}
// TODO: is there inter-track skew?
// TODO: it seems some tracks are skewed respective to others; investigate further.
// segment.rotate_right(3000); // Just a test, yo.
return std::make_shared<PCMTrack>(segment);
}
@ -223,7 +230,7 @@ void MacintoshIMG::set_tracks(const std::map<Track::Address, std::shared_ptr<Tra
const int data_rate = included_sectors.length * 6250;
// Decode the track.
auto sector_map = Storage::Encodings::AppleGCR::sectors_from_segment(
const auto sector_map = Storage::Encodings::AppleGCR::sectors_from_segment(
Storage::Disk::track_serialisation(*pair.second, Storage::Time(1, data_rate)));
// Rearrange sectors into ascending order.