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Corrects storage of lower two bit pairs.

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It turns out the non-integral result of 256/3 is handled differently than my guess.
This commit is contained in:
Thomas Harte 2018-04-29 11:20:23 -04:00
parent fabcb261dc
commit c62db6665a
1 changed files with 11 additions and 11 deletions
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22
Storage/Disk/Encodings/AppleGCR.cpp
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@ -115,9 +115,13 @@ Storage::Disk::PCMSegment AppleGCR::five_and_three_data(const uint8_t *source) {
Storage::Disk::PCMSegment segment;
segment.data.resize(410 + 7);
segment.data[0] = header_prologue[0];
segment.data[1] = header_prologue[1];
segment.data[2] = header_prologue[2];
segment.data[0] = data_prologue[0];
segment.data[1] = data_prologue[1];
segment.data[2] = data_prologue[2];
segment.data[414] = epilogue[0];
segment.data[411] = epilogue[1];
segment.data[416] = epilogue[2];
// std::size_t source_pointer = 0;
// std::size_t destination_pointer = 3;
@ -151,15 +155,11 @@ Storage::Disk::PCMSegment AppleGCR::six_and_two_data(const uint8_t *source) {
// contents; the 256 bytes afterwards are the remaining
// six bits.
const uint8_t bit_shuffle[] = {0, 2, 1, 3};
for(std::size_t c = 0; c < 85; ++c) {
segment.data[3 + c] =
static_cast<uint8_t>(
bit_shuffle[source[c]&3] |
(bit_shuffle[source[c + 85]&3] << 2) |
(bit_shuffle[source[c + 170]&3] << 4)
);
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 + 85] = bit_shuffle[source[255]&3];
for(std::size_t c = 0; c < 256; ++c) {
segment.data[3 + 85 + 1 + c] = source[c] >> 2;