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Corrects final two bytes of Apple GCR low nibble encoding.

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This commit is contained in:
Thomas Harte 2018-05-02 21:06:18 -04:00
parent af0cf0d40a
commit 4b4ea4a103
1 changed files with 17 additions and 4 deletions
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21
Storage/Disk/Encodings/AppleGCR.cpp
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@ -156,13 +156,26 @@ Storage::Disk::PCMSegment AppleGCR::six_and_two_data(const uint8_t *source) {
// six bits.
const uint8_t bit_shuffle[] = {0, 2, 1, 3};
for(std::size_t c = 0; c < 84; ++c) {
segment.data[3 + c] = bit_shuffle[source[c]&3];
if(c + 86 < 256) segment.data[3 + c] |= bit_shuffle[source[c + 86]&3] << 2;
if(c + 172 < 256) segment.data[3 + c] |= bit_shuffle[source[c + 172]&3] << 4;
segment.data[3 + c] =
static_cast<uint8_t>(
bit_shuffle[source[c]&3] |
(bit_shuffle[source[c + 86]&3] << 2) |
(bit_shuffle[source[c + 172]&3] << 4)
);
}
segment.data[87] =
static_cast<uint8_t>(
(bit_shuffle[source[84]&3] << 0) |
(bit_shuffle[source[170]&3] << 2)
);
segment.data[88] =
static_cast<uint8_t>(
(bit_shuffle[source[85]&3] << 0) |
(bit_shuffle[source[171]&3] << 2)
);
for(std::size_t c = 0; c < 256; ++c) {
segment.data[3 + 85 + 1 + c] = source[c] >> 2;
segment.data[3 + 86 + c] = source[c] >> 2;
}
// Exclusive OR each byte with the one before it.