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Switched to a track parsing that disallows synchronisation values within sector contents.

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This commit is contained in:
Thomas Harte 2016-12-31 12:23:08 -05:00
parent 12549ff412
commit cfbab1448c
1 changed files with 73 additions and 35 deletions
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108
Storage/Disk/Encodings/MFM.cpp
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@ -329,8 +329,10 @@ uint8_t Parser::get_next_byte()
std::vector<uint8_t> Parser::get_track()
{
std::vector<uint8_t> result;
size_t number_of_bits = 0;
bool is_clock = false;
int distance_until_permissible_sync = 0;
uint8_t last_id[6];
int last_id_pointer = 0;
bool next_is_type = false;
// align to the next index hole
index_count_ = 0;
@ -342,50 +344,86 @@ std::vector<uint8_t> Parser::get_track()
{
// wait until either another bit or the index hole arrives
bit_count_ = 0;
while(!bit_count_ && !index_count_) run_for_cycles(1);
bool found_sync = false;
while(!index_count_ && !found_sync && bit_count_ < 16)
{
int previous_bit_count = bit_count_;
run_for_cycles(1);
if(!distance_until_permissible_sync && bit_count_ != previous_bit_count)
{
uint16_t low_shift_register = (shift_register_&0xffff);
if(is_mfm_)
{
found_sync = (low_shift_register == MFMIndexSync) || (low_shift_register == MFMSync);
}
else
{
found_sync =
(low_shift_register == FMIndexAddressMark) ||
(low_shift_register == FMIDAddressMark) ||
(low_shift_register == FMDataAddressMark) ||
(low_shift_register == FMDeletedDataAddressMark);
}
}
}
// if that was the index hole then finish
if(index_count_) break;
// otherwise, add another bit to the collection if it wasn't a clock
if(!is_clock)
if(index_count_)
{
int bit = number_of_bits & 7;
if(!bit)
{
if(!result.empty()) printf("[%02x]", result.back());
result.push_back(0);
}
result[number_of_bits >> 3] |= (shift_register_&1) << (7 - bit);
number_of_bits++;
if(bit_count_) result.push_back(get_byte_for_shift_value((uint16_t)(shift_register_ << (16 - bit_count_))));
break;
}
is_clock ^= true;
// if a synchronisation is detected then align
uint16_t low_shift_register = (shift_register_&0xffff);
bool is_sync = false;
if(is_mfm_)
// store whatever the current byte is
uint8_t byte_value = get_byte_for_shift_value((uint16_t)shift_register_);
result.push_back(byte_value);
if(last_id_pointer < 6) last_id[last_id_pointer++] = byte_value;
// if no syncs are permissible here, decrement the waiting period and perform no further contemplation
bool found_id = false, found_data = false;
if(distance_until_permissible_sync)
{
is_sync = (low_shift_register == MFMIndexSync) || (low_shift_register == MFMSync);
distance_until_permissible_sync--;
}
else
{
is_sync =
(low_shift_register == FMIndexAddressMark) ||
(low_shift_register == FMIDAddressMark) ||
(low_shift_register == FMDataAddressMark) ||
(low_shift_register == FMDeletedDataAddressMark);
}
if(is_sync)
{
if(number_of_bits&7)
if(found_sync)
{
number_of_bits += 8 - (number_of_bits&7);
if(!result.empty()) printf("[%02x]", result.back());
result.push_back(get_byte_for_shift_value((uint16_t)shift_register_));
number_of_bits += 8;
if(is_mfm_)
{
next_is_type = true;
}
else
{
switch(shift_register_&0xffff)
{
case FMIDAddressMark: found_id = true; break;
case FMDataAddressMark:
case FMDeletedDataAddressMark: found_data = true; break;
}
}
}
is_clock = true;
else if(next_is_type)
{
switch(byte_value)
{
case MFMIDAddressByte: found_id = true; break;
case MFMDataAddressByte:
case MFMDeletedDataAddressByte: found_data = true; break;
}
}
}
if(found_id)
{
distance_until_permissible_sync = 6;
last_id_pointer = 0;
}
if(found_data)
{
distance_until_permissible_sync = 128 << last_id[3];
}
}