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Handle extra 0-bits at the start of a sector

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Jeff Epler
2022-03-01 11:50:26 -06:00
parent c4e4520058
commit d90fcbf7ad
1 changed files with 14 additions and 0 deletions
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14
arch/apple2/decoder.cc
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@@ -104,6 +104,20 @@ public:
if (readRaw24() != APPLE2_DATA_RECORD)
return;
// Sometimes there's a 1-bit gap between APPLE2_DATA_RECORD and
// the data itself. This has been seen on real world disks
// such as the Apple II Operating System Kit from Apple2Online.
// However, I haven't seen it described in any of the various
// references.
//
// This extra '0' bit would not affect the real disk interface,
// as it was a '1' reaching the top bit of a shift register
// that triggered a byte to be available, but it affects the
// way the data is read here.
auto p = tell();
auto b = readRawBits(1);
if(b[0]) seek(p);
/* Read and decode data. */
unsigned recordLength = APPLE2_ENCODED_SECTOR_LENGTH + 2;