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Switched parsing logic to looking only for upward zero crossings, that being my new understanding of the ROM.

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This commit is contained in:
Thomas Harte 2017-07-21 19:39:38 -04:00
parent a3e0024980
commit d69b1e2d11
1 changed files with 22 additions and 14 deletions
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36
Storage/Tape/Parsers/ZX8081.cpp
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@ -13,19 +13,25 @@ using namespace Storage::Tape::ZX8081;
Parser::Parser() : pulse_was_high_(false), pulse_time_(0) {}
void Parser::process_pulse(const Storage::Tape::Tape::Pulse &pulse) {
pulse_time_ += pulse.length;
// If this is anything other than a transition from low to high, just add it to the
// count of time.
bool pulse_is_high = pulse.type == Storage::Tape::Tape::Pulse::High;
if(pulse_is_high == pulse_was_high_) return;
bool pulse_did_change = pulse_is_high != pulse_was_high_;
pulse_was_high_ = pulse_is_high;
if(!pulse_did_change || !pulse_is_high) {
pulse_time_ += pulse.length;
return;
}
// Otherwise post a new pulse.
post_pulse();
pulse_time_ = pulse.length;
}
void Parser::post_pulse() {
const float expected_pulse_length = 150.0f / 1000000.0f;
const float expected_pulse_length = 300.0f / 1000000.0f;
const float expected_gap_length = 1300.0f / 1000000.0f;
float pulse_time = pulse_time_.get_float();
pulse_time_.set_zero();
if(pulse_time > expected_gap_length * 1.25f) {
push_wave(WaveType::LongGap);
@ -52,7 +58,7 @@ void Parser::inspect_waves(const std::vector<WaveType> &waves) {
return;
}
if(waves.size() >= 9) {
if(waves.size() >= 4) {
size_t wave_offset = 0;
// If the very first thing is a gap, swallow it.
if(waves[0] == WaveType::Gap) {
@ -67,10 +73,7 @@ void Parser::inspect_waves(const std::vector<WaveType> &waves) {
// If those pulses were followed by a gap then they might be
// a recognised symbol.
if(number_of_pulses > 17 || number_of_pulses < 7) {
push_symbol(SymbolType::Unrecognised, 1);
}
else if(number_of_pulses + wave_offset < waves.size() &&
if(number_of_pulses + wave_offset < waves.size() &&
(waves[number_of_pulses + wave_offset] == WaveType::LongGap || waves[number_of_pulses + wave_offset] == WaveType::Gap)) {
// A 1 is 18 up/down waves, a 0 is 8. But the final down will be indistinguishable from
// the gap that follows the bit due to the simplified "high is high, everything else is low"
@ -78,9 +81,9 @@ void Parser::inspect_waves(const std::vector<WaveType> &waves) {
// 17 and/or 7 pulses.
size_t gaps_to_swallow = wave_offset + ((waves[number_of_pulses + wave_offset] == WaveType::Gap) ? 1 : 0);
switch(number_of_pulses) {
case 18: case 17: push_symbol(SymbolType::One, (int)(number_of_pulses + gaps_to_swallow)); break;
case 8: case 7: push_symbol(SymbolType::Zero, (int)(number_of_pulses + gaps_to_swallow)); break;
default: push_symbol(SymbolType::Unrecognised, 1); break;
case 8: push_symbol(SymbolType::One, (int)(number_of_pulses + gaps_to_swallow)); break;
case 3: push_symbol(SymbolType::Zero, (int)(number_of_pulses + gaps_to_swallow)); break;
default: push_symbol(SymbolType::Unrecognised, 1); break;
}
}
}
@ -104,6 +107,9 @@ int Parser::get_next_byte(const std::shared_ptr<Storage::Tape::Tape> &tape) {
std::shared_ptr<std::vector<uint8_t>> Parser::get_next_file_data(const std::shared_ptr<Storage::Tape::Tape> &tape) {
if(is_at_end(tape)) return nullptr;
SymbolType symbol = get_next_symbol(tape);
if(symbol != SymbolType::FileGap) {
return nullptr;
}
while((symbol == SymbolType::FileGap || symbol == SymbolType::Unrecognised) && !is_at_end(tape)) {
symbol = get_next_symbol(tape);
}
@ -122,6 +128,8 @@ std::shared_ptr<std::vector<uint8_t>> Parser::get_next_file_data(const std::shar
std::shared_ptr<Storage::Data::ZX8081::File> Parser::get_next_file(const std::shared_ptr<Storage::Tape::Tape> &tape) {
std::shared_ptr<std::vector<uint8_t>> file_data = get_next_file_data(tape);
if(!file_data) return nullptr;
if(!file_data) {
return nullptr;
}
return Storage::Data::ZX8081::FileFromData(*file_data);
}