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Ensures that five-and-three sectors pass static analysis.

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This commit is contained in:
Thomas Harte 2020-07-16 21:44:14 -04:00
parent 4fec7c82ab
commit c7ef258494
1 changed files with 4 additions and 6 deletions
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10
Storage/Disk/Encodings/AppleGCR/SegmentParser.cpp
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@ -161,9 +161,7 @@ std::unique_ptr<Sector> decode_appleii_sector(const std::array<uint_fast8_t, 8>
sector->address.sector = ((header[4] << 1) | 1) & header[5];
// Check the header checksum.
// The 0x11 is reverse engineered from the game 'Alien Rain' and is present even on the boot sector,
// so probably isn't copy protection?
uint_fast8_t checksum = (((header[6] << 1) | 1) & header[7]) ^ (is_five_and_three ? 0x11 : 0x00);
const uint_fast8_t checksum = ((header[6] << 1) | 1) & header[7];
if(checksum != (sector->address.volume^sector->address.track^sector->address.sector)) return nullptr;
// Unmap the sector contents.
@ -205,7 +203,7 @@ std::unique_ptr<Sector> decode_appleii_sector(const std::array<uint_fast8_t, 8>
sector->encoding = Sector::Encoding::FiveAndThree;
} else {
// Undo the 6 and 2 mapping.
const uint8_t bit_reverse[] = {0, 2, 1, 3};
constexpr uint8_t bit_reverse[] = {0, 2, 1, 3};
#define unmap(byte, nibble, shift) \
sector->data[86 + byte] = uint8_t(\
(sector->data[86 + byte] << 2) | bit_reverse[(sector->data[nibble] >> shift)&3]);
@ -285,10 +283,10 @@ std::map<std::size_t, Sector> Storage::Encodings::AppleGCR::sectors_from_segment
// If this is the start of a data section, and at least
// one header has been witnessed, start a sector.
if(scanner[2] == data_prologue[2] || is_five_and_three) {
if(scanner[2] == data_prologue[2]) {
new_sector = std::make_unique<Sector>();
new_sector->data.reserve(710);
} else {
} else { // i.e. the third symbol is from either of the header prologues.
sector_location = size_t(bit % segment.data.size());
header_delay = 200; // Allow up to 200 bytes to find the body, if the
// track split comes in between.